Glomerulonephritis and Renal Failure
Glomerulonephritis, the commonest cause of end-stage renal failure in most countries, is worsened and may even be caused by exposure to chemicals present on many work places, at home and in the public environment.
The commonest nephrotoxic chemicals are hydrocarbons, present for instance in organic solvents, glues, fuels, paints and motor exhausts. Exposure is common among painters, printers, cabinet makers, fitters and mechanics, electricians, in much manufacturing, and in many other occupations
Also nephrotoxic are silicates, the main components in rocks and sand. Exposure is prevalent among miners, foundry and quarry workers, sandblasters, glaziers, and workers in the production and handling of asbestos, mineral wool and fiber glass.
Other chemicals that may promote glomerulonephritis or other kidney diseases include gold, lead, mercury and various drugs, for instance non-steroidal antiinflammatory drugs and lithium
Recent studies have found that even diabetic kidney disease may be worsened by exposure to toxic chemicals. Exposure should also be ruled out in patients with kidney diseases of unknown origin
As seen from the following more than 60% of patients with end-stage renal failure caused by glomerulonephritis have been exposed to toxic chemicals. Most important for patients with progressive renal failure is therefore to discontinue any exposure to nephrotoxic chemicals and drugs
Although glomerulonephritis is a rare disease, it is the commonest cause of end-stage renal failure in most countries. It is possible to live a normal life even with a substantial reduction of renal function, but when the function goes down below ten per cent of normal, symptoms such as muscular weakness, tiredness, itching, anemia and nausea may eventually invalidate the patient seriously. This condition is called end-stage renal disease and may soon become life-threatening.
Previously, all patients with end-stage renal disease died, but to-day it is possible to maintain life by dialysis treatment or by transplanting a kidney from another human being. However, it is still a catastrophe for the patient and the patient´s family because there is a great shortage of kidneys for transplantation, and dialysis treatment is disabling. Two to three times a week the patient is chained to a dialysis machine for many hours and despite that the patient`s health is not optimal. A tedious diet and many drugs are necessary to combat the many complications of end-stage renal failure and the mortality is high. Every year 20-30 per cent of all dialysis patients die, but new patients constantly arrive. Therefore, although glomerulonephritis is a rare disease it is costly for society. In many countries treatment of renal failure alone takes four to five per cent of the total health budget.
Glomerulonephritis is an innocent condition as long as the renal function is normal. The “patient” has no symptoms and the diagnosis may remain undetected unless his urine is examined. Here, a, routine laboratory test may reveal the presence of small amounts of protein and blood in the urine (named proteinuria and hematuria, respectively), and with a microscope, red blood cells and casts of the renal tubules may be seen also. If a patient with these findings is admitted to a renal department for further investigations it is likely that the doctor with a fine syringe will take out a small sample of the kidney tissue, a so-called kidney biopsy. A microscopic analysis of the kidney tissue most often, but not always, will reveal deposits of immunoglobulins and/or complement factors in the glomeruli, the minute filters of the kidney. In spite of these laboratory abnormalities the “patient” may remain healthy for the rest of his life.
I have guarded the word patient with quotation marks because, as I shall argue in the following, it is doubtful if the presence of immune components in the glomeruli alone, or the findings of slight urine anomalies, is a disease.
Glomerulonephritis may also appear acutely, often in association with an upper respiratory infection, but even spontaneously. Acute glomerulonephritis has usually a benign course, even in cases where the renal function is seriously affected in the acute stage, as the function recovers completely in most patients.
But in some patients glomerulonephritis may be associated with the nephrotic syndrome, a high blood pressure and a decreased renal function. If these complications do not occur in association with an acute onset as described above, but rather appear gradually and insidiously, these abnormalities will most often, sooner or later, proceed to end-stage renal failure.
This is the greatest challenge for researchers in nephrology to-day, to understand why, once renal function has worsened, most cases of glomerulonephritis and other diseases of the kidney tissue progress to end-stage renal failure, irrespective of any treatment.
In the following I shall present a hypothesis, that explains the cause of progressive renal failure in many patients, a hypothesis that is based on solid scientific evidence, but is ignored or met by disbelief by most nephrologists.
The aim of the website is not only to inform colleagues, but also patients and their relatives. Therefore I have tried to present the text in a way so that it should become understood by a layman. Certain scientific terms are explained on a separate file. These words are marked as hyperlinks – just click on it and use the back button to get back to the text. Here I have also given references to the relevant scientific literature. If you are unfamiliar with the way scientists present or search information, but are interested in deepening your knowledge, go to a university library with the references and ask the librarian for help.
According to current concepts glomerulonephritis is an immunologic disease. Immune complex formation, the reaction between antibody and antigen, is said to occur in the glomeruli, the microscopic globular capillary filters of the kidney. When immune complexes are formed, various enzymes in the blood and on the surface of the cells, the so-called complement factors, are activated by the reaction, and the complement factors together with other chemical processes that are initiated by them, allegedly destroy the glomerular filtering apparatus and sooner or later the whole kidney.
In a particular type of glomerulonephritis called minimal change nephropathy it is not the formation of immune complexes that is considered detrimental, but the white blood cells´ production of lymphokines. One of their effects is that they increase the permeability of the glomerular basement membrane.
The above is a very simple presentation of the current view. In the following I shall give some more detailed explanations and arguments for the concept. Authoritative and comprehensive reviews can be found elsewhere (1-6). However, to follow my arguments for the new toxic-allergic hypothesis it is not necessary to understand all details of the immunological concept.
As I shall demonstrate in the following, there are numerous experimental and clinical observations that are in serious conflict with the classical concept. The aim of this website is to question this concept and to present a new theory about the causation of glomerulonephritis, in particular to explain why the disease in some patients proceeds to renal failure and how it may be possible to stop and even reverse this process. The theory and the numerous studies that support it, have been presented in medical journals since many years. By unknown reasons the issue has gained little interest among nephrologists and little is mentioned about the subject in the textbooks.
In the present review I have concentrated on the association between hydrocarbon exposure and glomerulonephritis because this is the area that has been studied most thoroughly and this is also the most widespread type of toxic exposure. Among other chemicals that have been associated with glomerulonephritis are silicon, mercury, lithium and gold. Many drugs are known to be able to induce glomerulonephritis also; the most important ones are a type of pain-killers called non-steroidal-antiinflammatory-drugs, or NSAID, but also lithium and certain antibiotics. In the following I shall discuss the importance of silicon compounds and NSAID. Hopefully I shall be able to update the website later on with more information about other types of toxic exposure.
In the following I shall present the arguments for the classical concept and after each argument my counter-argument. After that I shall tell you about the new toxic-allergic hypothesis and the scientific evidence for that idea and also explain why the clinical and experimental findings fit much better with the toxic-allergic hypothesis than with the classical concept.
Although I have tried to explain the many arguments for and against the classical concept in a popular way they may appear rather complicated if you are unfamiliar with biological science. Therefore, if you are not a doctor or a researcher and if you find the arguments too complicated I will suggest that you precede directly to the toxic-allergic hypothesis. For the experienced researcher more comprehensive reviews of the arguments can be found elsewhere (7-12).
This website is based on the medical literature. Click on the names of the authors in the text to get the references. In a few of the more recent papers there is a link to the abstract of the article also. Reprints of the most recent of my own papers are still available.
As mentioned above, glomerulonephritis often starts 1-3 weeks after an infectious disease at a time where the body´s immune system is working hardest to combat the infection. The best studied variant is acute poststreptococcal glomerulonephritis, a particular type of glomerulonephritis that appears after an infection of the throat or the skin with certain strains of streptococci (a type of bacteria), the so-called nephritogenic strains. The start of a kidney disease shortly after the start of an infection strongly suggests that the infection, or the immune response that it has elicited, is an important causal factor.
The close association between an infection and the onset of the disease is a good argument for the idea that the immune system is involved in some way, but it does not prove that the infection or the immunological reactions by themselves is the very cause. The large majority of infectious diseases are not associated with glomerulonephritis, and many cases of glomerulonephritis are not initiated by an infectious disease indicating that an infectious process alone is insufficient and not even necessary to produce the disease. Evidently, there must be contributing factors, either hereditary, or environmental, or both.
A strong case for a participating role of hydrocarbon exposure in poststreptococcal glomerulonephritis is the following observation. Fifteen patients with poststreptococcal glomerulonephritis and fifteen patients who had had an infection with a nephritogenic streptococcal strain without developing glomerulonephritis were asked about possible exposure to organic solvents, fuels, glues or other hydrocarbons timely associated with the onset of the disease (13). Ten of the patients with glomerulonephritis had been exposed during the period between the streptococcal infection and the acute onset of the nephritis, whereas none of the control individuals reported exposure timely associated with their infection. In some patients the exposure was heavy, but short and confined to the mentioned period only; others had been exposed less heavily, but during long periods before the streptococcal infection. All exposed patients were ten years or older, five of them were adults, whereas four of the five unexposed patients were preschool children attending a daytime nursery and the interview of these children was performed six months to three years after recovery from the acute glomerulonephritis. Exposure may thus have occurred without the parents knowing or it may have been forgotten by them.
Another interesting observation from this study was the result of a follow-up study. Four of the patients had been exposured also after the acute onset of the disease, three of them had renal failure. The other eleven had not been exposed, nine of them had normal renal function, two had an insignificant lowering.
The logical explanation from this study is that a streptococcal infection, even with strains that are especially known to produce glomerulonephritis, does not harm the kidneys unless the patient is exposed at the same time for nephrotoxic chemicals. Either the chemicals make the kidneys susceptible to immunological harassment, or the chemicals enhance the renal damage by attacking another part of the kidneys, the tubules, and the combined effects of the immunological reactions and the toxic damage may produce the serious kidney disease. The study also points to the influence of continued exposure on renal function.
In this connection it is worth mentioning that epidemics of acute poststreptococcal glomerulonephritis have been described from oil-producing areas such as Trinidad and Macaraibo in Venezuela (14,15) and here the disease often progressed to renal failure, whereas acute poststreptococcal glomerulonephritis usually is a benign disease, at least in children. Also, in most countries glomerulonephritis has become a rare disease, but not in Kuwait, a small country where a large proportion of the population is engaged in the oil industry (16).
In most patients with glomerulonephritis a microscopic investigation of the renal tissue using immunofluorescence microscopy shows deposits of antibodies and complement factors in the glomeruli. The presence of both antibodies and complement in the glomeruli strongly suggests that a formation of immune complexes has taken place with unfortunate consequences for the glomerular filters. Plasma proteins, that normally are unable to pass the glomerular basement membrane because of their size, now leak to the urine and eventually, renal function goes down.
Immune complexes in the glomeruli may have been formed outside the kidneys and thereafter trapped in the glomeruli. Even if they have been formed in the glomeruli, their formation may not necessarily damage the kidneys, as has been demonstrated in numerous animal experiments (see later).
That the mere presence of immune complexes in the glomeruli may be unimportant for glomerular function is obvious from numerous clinical observations. For instance, patients with cancer, various internal diseases, and even healthy individuals, often have immune complexes located to the glomeruli without having any signs or symptoms of renal disease (17-24). Glomerular immune complexes are also found in normally functioning kidney grafts (25). Very often such findings have been classified as glomerulonephritis, but to call a deposition of immune complexes for a kidney disease when the kidneys are functioning normally and the urine is normal, is misuse of medical terminology.
There are disturbing observations from the animal kingdom also. Great amounts of glomerular immune deposits have been found in a large proportion of sheep, steers, guinea pigs, horses, mice and rabbits with normal urine and normal kidney function (26-31). Again, these findings have been classified as glomerulonephritis, but if the presence of immune complexes alone is a disease you could equally well call dirty nails for a disease.
Also, if a glomerular formation of immune complexes were the direct cause of glomerulonephritis, the amount of immune complexes should correlate with the renal function and the course of the disease. Patients with many deposits should more often have renal failure than patients with little or no deposits, and many deposits should also mean that the disease has a more serious outcome, this is pure logic. But there is no association whatsoever between the amount of glomerular deposits or the degree of glomerular damage, and the renal function and the outcome; this has been documented in numerous studies (32-35). In fact, about a fifth of all patients with serious glomerulonephritis have no glomerular deposits at all.
Another fact, that has gained little interest among nephrologists is that many patients with glomerulonephritis have deposits of immunoglobulins but not of complement. If the disease were the result of immune complex formation in the glomeruli, both immunoglobulins and complement should be present because complement is always participating in the formation of an immune complex.
These observations are difficult to understand if the classical hypothesis were true, but as seen in the following they are easily explained by the toxic-allergic hypothesis, which says that the deposits are secondary to the real cause, the toxic-allergic damage of the tubulointerstitial tissue and the glomerular basement membrane. Any macromolecule may be caught in the glomerular filters, in particular if the glomerulus is damaged by toxic or allergic reactions. In the following sections I shall tell about the many studies that in various ways have shown that the depostion of immune components in the glomeruli is a secondary phenomenon secondary to the toxic-allergic damage of the kidneys.
In a special type of glomerulonephritis, the so-called anti-glomerular-basement-membrane (anti-GBM) nephritis, antibodies against the glomerular basement membranes (shortened GBM) are found in the blood of the patients during active periods of the disease. By immunofluorescence microscopy such antibodies are also found lying closely to the GBM as a linear band. These findings strongly suggest that the attack of the antibodies on the GBM is the cause of the disease.
Anti-GBM antibodies are found now and then in the blood and even in the kidneys of healthy individuals without any clinical signs of glomerulonephritis (36-38). They have also been found in the blood of transplanted patients whose own kidneys allegedly have been destroyed by anti GBM-nephritis (39). But although the same antibodies still were present in the blood and even located in the transplanted kidney, the latter was completely normal. As these anti-GBM antibodies were blamed for having destroyed the patient´s own kidneys, but did not harm the transplanted kidney, an attack of such antibodies alone cannot explain the serious disease.
An important co-factor must be necessary, a factor that was present when the patient became sick, but was absent after the transplantation. The factor may for instance have been an exposure to nephrotoxic chemicals. In accordance, a large numer of case stories have been published where anti-GBM nephritis had been preceded by heavy exposure to various kinds of toxic chemicals closely time-asociated with the acute onset of the disease.
(In fact, most of the published case histories of glomerulonephritis associated with toxic exposure concern this very rare type of glomerulonephritis. This fact has of course been used by those who are skeptic to the association in general. How come that this rare variant predominates among the case stories? Why haven’t more case histories about exposed patients with the common variants of glomerulonephritis been published? The reason is simple. Anti-GBM nephritis is very often followed by lung bleedings, the so-called Goodpasture´s syndrome. A patient with glomerulonephritis and lung bleedings automatically stimulates the doctor to ask for toxic airborn exposure. Unfortunately, few doctors asks patients with glomerulonephritis alone.)
Many immunologic functions are disturbed in glomerulonephritis. The number of a special type of white blood cells, the T-cells may be lowered and their function may be imperfect. Also other kinds of white blood cells do a bad work, and the production of antibodies is decreased or abnormal (Ravnskov 1985). For instance, antibodies may be produced that are directed against the patients own tissue, in particular against the renal cells, a condition called autoimmunity. These findings clearly indicate that a disturbance of the immune system is an important factor in the causation of the disease.
Disturbances of the immune system are in accord with both hypotheses because almost all chemicals that have been associated with glomerulonephritis, inhibit or derange the immune system (Ravnskov 1985). Again, immunological processes may participate in the creation of glomerulonephritis, but they are not necessarily the very cause.
Numerous experimental models have demonstrated that glomerulonephritis can be produced in animals by immunological methods. In one of the first models, acute or one-shot serum sickness, rabbits were injected with bovine serum albumin. A few days´ later, when the rabbit´s immune system has started to produce antibodies against the injected antigen, typical acute glomerulonephritis with proteinuria and haematuria develops, a strong argument that an acute infection may induce glomerulonephritis (40). The injected antigen, the bovine serum albumin molecules, are caught in the glomerular filters and when the antigens are attacked by the rabbit´s anti-bovine-albumin antibodies the resulting formation of immune complexes injures the glomeruli. If several injections of bovine albumin are given (chronic serum sickness), the rabbit eventually may develop serious glomerulonephritis with impaired renal function (41).
No doubt, the acute serum sickness model is a good simulation of human, acute glomerulonephritis. However, no serious or persistent renal damage is produced after a single injection of foreign serum albumin. Just as in most human types of acute glomerulonephritis, the only symptoms are transient proteinuria and haematuria at most and the renal function remains normal. In numerous similar animal models the researchers have claimed that they have produced glomerulonephritis. The only thing that has been produced however, is a formation or deposition of immune complexes in the glomeruli followed by mild and transient urinary abnormalities, or less than that.
Let me stress again: a deposition of immune complexes in the kidneys (or elsewhere) without any other symptoms is not a disease. In all mammals, including human beings, there is normally a steady production of immune complexes in the body. This is part of the normal defense against foreign molecules and microorganisms. Immune complexes are disposed by various ways as garbage and may be found in many parts of the body, including the glomeruli, in all healthy individuals. Glomerulonephritis is a clinical problem, or a serious disease, only if it is followed by kidney failure or the nephrotic syndrome. (You may add also: a high blood pressure, but a high blood pressure rarely appears in the absence of renal failure or the nephrotic syndrome).
The chronic serum sickness model seems to be a good argument for the classical hypothesis. However, to induce serious glomerulonephritis it is necessary to inject large amounts of the antigen several times during several weeks. In most human infections bacterial or viral antigen rarely appear during longer periods in the blood circulation because it is quickly eliminated by our immune system. But there are exceptions. Serious glomerulonephritis may be seen associated with chronic infections, such as hepatitis, malaria, schistosomiasis, and an infected atrioventricular shunt. In these diseases the steady discharge of microbial antigens into the blood may be a contributing and perhaps even the main cause of glomerulonephritis. In accordance, glomerulonephritis secondary to chronic bacterial infections are most often cured by antibiotics directed against the infectious agent, whereas antibiotics have no effect on other types of glomerulonephritis, not even on glomerulonephritis secondary to an acute infection.
If a rat is immunized with certain extracts of its own kidney a severe glomerulonephritis develops. Immune complex formation inside the glomeruli leads to severe proteinuria and eventually renal failure (42-43). This is a strong argument that an immunological reaction inside the glomeruli is the cause of glomerulonephritis.
To develop serious glomerulonephritis in this animal model it is necessary to mix the injected tissue extract with Freund´s adjuvant. This substance is a mixture of mycobacteria emulsified with mannide monooleate in hydrocarbon oils and has been used in countless animal experiments to enhance the immunological reactions. It is a striking fact, however, that in experimental glomerulonephritis no serious kidney damage is produced without the use of Freund´s adjuvant. In the section Experimental Anti-GBM Nephritis I shall show that the reason why Freund’s adjuvant produces glomerulonephritis is not an enhancement of the immunological reactions but a toxic effect on the kidneys.
What also has been ignored is that an injection of Freund’s adjuvant alone produces typical glomerulonephritis with deposition of immune complexes in the glomeruli (8,45). This means that experimental glomerulonephritis produced with the aid of Freund’s adjuvant cannot be used as support of the classical concept, because who knows if it is the immunization, or the injection of the nephrotoxic substance, Freund’s adjuvant. or a combination of these measures, that are producing the disease?
The similarity with acute poststreptococcal glomerulonephritis is striking: a streptococcal infection without exposure to toxic chemicals may be harmless (44) just as an immunization of the rat without the use of Freund´s adjuvant is harmless. The similarity goes further, because just as an injection of Freund´s adjuvant can produce glomerulonephritis by itself, hydrocarbon exposure alone can do it also. This has most convincingly been demonstrated by the animal experiments.
However, even if Freund´s adjuvant alone can produce glomerulonephritis, the disease becomes more serious if the injection is combined with an immunization. Obviously the immune system is participating in the production of glomerulonephritis, but it is not causing it by itself.
Antibodies against the rat kidney can be produced in rabbits by immunization of the rabbit with injections of a rat kidney extract into the rabbit. If these rabbit anti-rat kidney antibodies are injected into a rat they will immediately attack the rat´s glomeruli After a number of injections the rat develops glomerulonephritis with renal failure, a strong argument for the idea that an immunological reaction in the glomeruli alone can produce serious glomerulonephritis (46,47).
This type of experimental glomerulonephritis develops in two steps. In the first stage, the heterologous phase, the rabbit anti-rat-kidney antibodies (the foreign, or heterologous antibodies) attack the rat´s glomeruli. At this stage a granular deposition of complement factors and rabbit antibodies are seen in the glomeruli. But this reaction does not result in any kidney damage and no proteinuria is seen. The second stage, the autologous phase, begins a few days later. As the injected anti-rat kidney antibodies come from another species, they are recognized as “foreign” by the rat´s immune system. Consequently, the rat starts to produce antibodies against the foreign antibodies. At this time, both rabbit and rat antibodies are seen in the glomeruli.
A reaction between antigen and antibody is the starting signal for inflammation. Normally, an inflammatory reaction protects us against foreign intruders such as bacteria, virus and other foreign substances. In the autologous phase the antibodies attack the foreign rabbit antibodies, that are located to the glomerular basement membrane. Therefore, the inflammation may destruct not only the intruders, but also the basement membrane.
The reason why the first reaction, the heterologous phase, does not damage the kidney but the second does, may partly be that the second involves many more antibodies, and partly because the second reaction happens to a membrane that is already damaged a little, just as a flu is harmless in healthy youngsters but can kill the old and the weak. By this way the GBM of the rat is damaged both from the immune complex formation between the injected, foreign anti-kidney antibodies and certain parts of the GBM, but also from the reactions between the rat’s own antibodies, the autologous antibodies, that are attacking the injected rabbit antibodies and thus indirectly also the GBM.
That it is the second reaction, the autologous phase that is crucial has been shown in an elegant variant of the experiment. Here, the rats were made tolerant to rabbit immunoglobulin by desensibilization before the experiment. As a result no renal damage was seen; the autologous phase had been eliminated (48).
Even if it were correct that glomerulonephritis in the passive Heymann nephritis is produced by immunological means only, the mechanism is of course highly unlikely in human beings, because no one would ever have injected anti-human antibodies. To assume that the passive Heymann nephritis is a model of human glomerulonephritis should demand that the patient produces antibodies against his own GBM, but also, at the same time, produces antibodies against his own immunoglobulins, a hitherto unknown combination of events in glomerulonephritis.
It is possible to demonstrate in another way that the rat’s own anti-kidney antibodies alone are unable to hurt the kidney. If anti-kidney antibodies (extracted from a rat with active Heymann nephritis) are injected into a healthy rat, these antibodies immediately locate to the glomeruli together with complement, indicating that an antigen-antibody reaction has taken place in the glomeruli. But no kidney damage is seen, just as no damage was seen during the heterologous phase. The urine is normal as is the renal function, clearly indicating that a direct immunological attack against the glomeruli is harmless – a crucial factor is missing (9,49-51).
An immunization of experimental animals with extracts of the glomerular basement membrane (GBM) mixed with Freund´s adjuvant produces serious glomerulonephritis. In this type of glomerulonephritis the antibodies and the complement factors are seen by immunofluorescence microscopy as a fine, linear band along the GBM (52,53). This finding clearly demonstrates that the anti-GBM antibodies are attacking the GBM. The reaction between antibodies and antigen is followed by immune complex formation and inflammation, strongly suggesting that the kidney damage is caused by this reaction.
Again, serious glomerulonephritis is produced only if Freund´s adjuvant is used; an immunization alone does produce a linear deposition of antibodies and complement but it does not produce proteinuria or renal failure. As mentioned previously Freund´s adjuvant produces glomerulonephritis alone (44). Therefore, the mentioned experiment is no proof that immunological reactions alone are causing glomerulonephritis. Most probably, Freund´s adjuvant sensitises the kidneys for immunological assaults. This is suggestive from the following experiment.
At first, rats were injected with Freund´s adjuvant alone. After 2-3 weeks rabbit anti-rat-GBM antibodies were injected into these rats in 1/20-1/15 of the amount required to produce glomerulonephritis in the Masugi model (see below). Control rats, that had not been pre-treated with Freund´s adjuvant, were injected with antibodies too. The pre-treated rats developed glomerulonephritis in two steps, just as in the Masugi nephritis (see below) and in the passive Heymann model, whereas no damage was seen in the rats that were not pre-treated with Freund´s adjuvant (54).
Evidently, Freund´s adjuvant is an important co-factor in this experiment. The difference was not due to a stronger immunization of the rats that had been injected with Freund´s adjuvant because the amount of antibodies extracted from their kidneys was not larger than the amount of antibodies extracted from the kidneys of the rats in the control group. Again, the most reasonable conclusion is that Freund´s adjuvant predisposes the kidneys to immunological harassment (Ravnskov 1989).
The experimental induction of anti-GBM nephritis is not dependent on Freund´s adjuvant because it is also seen after injection of foreign anti-GBM antibodies alone (foreign, or heterologous: from another animal species), just as passive Heymann nephritis can be produced by injecting foreign anti-kidney antibodies (53).
Again, just as in passive Heymann nephritis, this type of glomerulonephritis can be separated into two steps. The first step, the heterologous phase, is followed by trace proteinuria at most and no renal damage is seen. At this stage only rabbit antibodies can be seen in the glomeruli. A few days later a serious glomerulonephritis may develop. At this stage, the autologous phase, the rabbits own antibodies can be seen in the glomeruli also, obviously attacking the foreign antibodies that are located along the glomerular basement membrane. Thus, two immunological process are taking place in the glomeruli: immune complex formation between the foreign (heterologous) anti-GBM antibodies and the GBM, which is harmless; and immune complex formation between the rat´s own (autologous) antibodies and the foreign antibody. And again, the second reaction can be abolished if the animals are made tolerant to the injected, foreign antibodies before the experiment (55).
Once again it has been demonstrated that a direct attack on the kidney by one´s own antibodies does not produce glomerulonephritis. A crucial factor is missing.
According to this hypothesis the first and causal event in glomerulonephritis is not an infection or an immunological reaction in the glomeruli, but an exposure to nephrotoxic chemicals, either by inhalation, by skin contact or by ingestion. The precise mechanism by which the chemicals produce renal damage is still uncertain, but the primary targets are most probably the tubular cells and/or the cells of the immune system. The deposition of immunoglobulins and complement in the glomeruli is a secondary phenomenon with little importance for glomerular function or structure (Ravnskov 1985, Ravnskov 1989, Ravnskov 1998, Ravnskov 1999).
The tubular cells have many important functions in the body. They regulate the balance of salt and water in the blood, they maintain the body’s acid/base balance, they prevent important substances from being lost in the urine after having been filtered out through the glomerular filters, and many toxic substances are taken up from the blood and secreted into the urine by these cells. The latter function is probably crucial for the start of glomerulonephritis because if too much of a toxic chemical has come into the blood, its accumulation in the tubular cell may damage and even kill the cell. The damage of the tubular cells may lead to inflammation and scarring of the interstitium. These changes lead to shrinkage of the renal tissue, the tubules become narrow,the urine flow is retarded, and gradually renal function goes down.
Another possibility is that white blood cells react with the chemical and starts an allergic reaction. Also this reaction may lead to inflammation in the interstitium. White blood cells may become stimulated by the allergic reaction to produce lymfokines, small molecules that may damage the epithelial cells of the GBM resulting in an increased permeability to plasma proteins and facilitate the deposition of macromolecules, for instance antibodies and complement factors, in the glomeruli. Such damage may even be produced directly by the toxic chemicals. Most probably all mechanisms operate together.
If the toxic-allergic hypothesis is correct the following predictions should be satisfied:
- Workers exposed to nephrotoxic chemicals should more often have symptoms of glomerulonephritis than other people.
- Patients with glomerulonephritis should have been exposed more often to nephrotoxic chemicals than other people.
- Patients with glomerulonephritis and a decreased renal function should have been exposed more often than patients with glomerulonephritis and normal function.
- Discontinuation of the exposure should improve renal function and the course of the disease.
- The renal function and the course should be closer associated with the tubulointerstitial changes than with the glomerular changes.
- Exposure of laboratory animals to nephrotoxic chemicals should produce glomerulonephritis with renal failure.
In the following I shall show that all of these predictions have been fulfilled.
In a cross-sectional study signs of the disease is sought in individuals exposed for the suspected causal factor and in non-exposed individuals of the same age and sex. If the factor is causal, the disease should be seen more often in the exposed than in the unexposed individuals.
A large number of cross-sectional studies of workers with occupational exposure to hydrocarbons have been published. These studies included refinery workers, dry-cleaners, floor layers , printers, road workers, paint sprayers and a variety of other workers exposed to organic solvents or fuels. In at least fourteen studies these workers had more often urinary findings typical for early glomerulonephritis than had the unexposed control individuals (56-70). In three of the studies the workers even had a decreased renal function more often (61,66,70).
Thus, without doubt, exposure to hydrocarbons does induce renal damage typical of glomerulonephritis. It should be stressed, however, that it was seen only in a few of the exposed workers, and that these workers were healthy by all standards and had no other symptoms or signs of disease. The blood and urinary findings were mild in most workers and may have remained undetected if the laboratory tests had not been performed. What these studies have shown is that hydrocarbon exposure affects the kidneys of a few individuals but to a small degree only.
As hydrocarbon exposure is prevalent in most societies and as clinically significant glomerulonephritis is a rare disease, a further factor, probably a hereditary predisposition, is necessary. If this unknown factor is present, however, hydrocarbon exposure may result in serious glomerulonephritis. This has been shown most convincingly by the case-control studies.
In a case-control study a number of patients with the disease in question (here glomerulonephritis) are asked whether they have been exposed to the risk factor (here toxic chemicals) more often than a similar number of control individuals without the disease and of the same age and sex.
Today, twenty case-control studies of patients with glomerulonephritis and healthy control individuals or patients with various non-renal diseases have been published. In the large majority of these studies patients with glomerulonephritis had been exposed more often to hydrocarbons (mainly fuels, glues, paints, solvents and motor exhausts) than had the control individuals (11,12). In a few studies the exposure difference was trivial, but two of them included only patients with early stages of the disease (71,72), and two studies included one group of patients with normal or mildly reduced renal function and little exposure, and one group of patients with chronic renal failure and much exposure (73,74). In four studies, that included patients with end-stage renal failure only, 60-80 per cent of the patients had been exposed (75-78).
An exception is a population-based case–control study of 926 patients with renal failure, 222 of whom had glomerulonephritis, and 998 control subjects matched for age and gender (79). In that study, no difference was found with regard to the degree of renal failure between exposed and unexposed patients, including those with glomerulonephritis. The authors, therefore, claimed that organic solvents have no adverse effect on the development of renal failure.
The study had several serious errors, however. Statisticians, who were not blinded to the patient’s case–control status, interviewed the subjects; occupational hygienists were only involved, if the patient reported exposure to solvents. A kidney biopsy specimen was available in only 61% of the patients. Diagnoses of underlying renal disease were based on routine clinical evaluation, and as the study included patients from all the hospitals in the country, some of the diagnoses must have been made by non-nephrologists. The most serious bias was the exclusion of patients who had died before the interview, patients who were too ill to be interviewed and patients who had received a kidney transplant, because all other studies have shown that exposure is most pronounced in such patients.
Thus, taking all studies together, a strong, inverse association was found between degree of exposure and renal function, and a direct association between degree of exposure and stage of the disease indicating that the most important effect of the exposure is a worsening of renal function (11).
Patients with glomerulonephritis and normal or only slightly depressed renal function may not necessarily have been exposed more than most of us who live in a western society, whereas patients with glomerulonephritis and more advanced renal failure have been exposed more often, in particular patients with end-stage renal failure.
However, even if two studies that included acute glomerulonephritis did not find an increased exposure to hydrocarbons we cannot exclude that such exposure also may start glomerulonephritis because some individuals may be more sensitive to hydrocarbon exposure than others. If so, a short, but intensive exposure may suffice to start the disease, but as most people experience such exposure once or perhaps several times in their life, the total exposure of patients with early glomerulonephritis may not necessarily exceed the exposure of most people. To know if a short exposure may start the disease it is necessary to study the timely association between the exposure and the onset of the disease. One of the case-control studies had addressed this question. As mentioned in the section named The postinfectious occurrence the acute onset of the disease was closely time-associated with exposure to organic solvents in ten of the fifteen patients.
In a cohort study a number of healthy individuals (the cohort) are followed during a period of time. Either all individuals are exposed and the frequency of the disease is compared with the frequency in the general population, or the cohort could represent a random sample of the population. In the latter case the suspected disease factor is asked for among those who have acquired the disease at follow-up and those who have not. However, the rarity of glomerulonephritis demands that a conventional cohort study should include at least 22000 exposed individuals to be able to demonstrate a statistically significant increase of the disease (80).
Instead of recording new cases among healthy individuals, renal function and degree of exposure can be recorded in patients with established disease.
In one such study fifty patients with glomerulonephritis were followed for 7-8 years. At follow-up nine of 26 patients, who were heavily exposed to hydrocarbons, had end-stage renal failure, but this was not seen in any of 24 moderately or rarely exposed patients (81).
In a more recent study 68 patients with glomerulonephritis were followed for five years. At follow-up 21 of 29 patients with progressive renal failure had been exposed to hydrocarbons, whereas exposure was noted only in five of 39 patients with stable renal function. Furthermore, it was noted that when the exposure was eliminated in these five patients, their renal function improved (82).
Together with the case-control studies these two studies show that the most important effect of hydrocarbon exposure is a worsening of renal function. The logical conclusion is of course that all patients with glomerulonephritis and renal failure should be questioned in depth about possible toxic exposure and if such exposure is present, attempts should be performed to eliminate the exposure. As I shall demonstrate soon, an attempt to do that in a few patients was succesful.
When researchers claim a factor for being the cause of a disease one of the strongest proofs is the induction of the disease in an experimental animal with the suspected disease factor. When it comes to glomerulonephritis and hydrocarbons such experiments have been performed succesfully again and again in rats, mice, cats and guinea pigs. Here is a list of the hydrocarbons that have been used:
Type of glomerulonephritis
|Diacetylbenzidine||Proliferative with crescents (83)
Not classifiable (84)
Not classifiable (85)
Rapidly progressive (86)
Not classifiable (exsudative?) (87)
Focal, segmental sclerosis (88)
|Tetramethylbenzidine||Not classsifiable (84)|
|Trichloroethylene||Not classifiable (89)
Not classifiable (90)
Not classifiablen (91)
Not classifiable (92)
|Trimethylpentane||Not classifiable (93)|
|Xylen||Not classifiable (94)|
|Petrol (gasoline)||Focal, mesangial (95)|
|Carbon tetrachloride||Minimal change, glomerulosclerosis (96)
IgA nephritis; focal sclerosis (97)
Focal, segmental sclerosis (88)
Mesangial; focal segm. sclerosis (99)
|Dinitrochlorobenzene + acetone||Mesangial (exsudative?)(100)
Anti-TBM; focal segm. proliferative (101)
Anti-TBM; minimal change; focal segm. prolif. (102)
|Maleic vinylether anhydride||Minimal change (103)|
|Bromoform, dibromochlorometan||Not classifiable (104)|
|White spirit||Not classifiable (105)|
Some of the early studies were rather primitive and did not allow a more specific classification. In the studies where modern microscopic techniques were used most of the human subgroups of glomerulonephritis were identified as seen from the table. Tubular damage was noted in all experiments; renal function was measured in eight and was decreased in five. In the studies, where the animals were examined at different times during or after the exposure, the tubular changes were observed immediately, whereas the glomerular deposition of IC and complement appeared late in the course.
In a recent review I have analysed the animal experiments in more detail (Ravnskov 2005)
Evidently we cannot test the hypothesis by exposing human beings for hydrocarbons. But an unintentional “experiment” was performed some years ago i Spain. Adulterated cooking oil that contained aniline, oleoanilides and azobenzene, was sold for human consumption. 842 patients were admitted to hospital with severe symptoms of intoxication. Four of them had glomerulonephritis with renal failure. As this number is at least 150 times higher than the normal incidence of end-stage glomerulonephritis during a whole year there can be no doubt that the glomerulonephritis was caused by the chemicals (106).
Instead of exposing healthy individuals we can ask exposed patients to discontinue the exposure and see what happens. Only one such study has been published. In that study fifteen of thirty exposed patients discontinued the exposure. Initially the renal function in these patients was lower and the blood pressure higher compared with the fifteen patients who did not succeed in discontinuing the exposure. In spite of that the course of the disease was more favourable (Ravnskov 1986), just as in the follow-up studies by Bell et al and Yaqoob et al (81,82).
Evidently, the most important influence of hydrocarbon exposure in glomerulonephritis is its effect on renal function. Exposure is prevalent in patients with renal failure and renal function may improve when the exposure is discontinued.
Treatment with certain analgesics, named non-steroidal-antiinflammatory drugs, or NSAID, may in rare circumstances induce a renal disease. In some patients the disease develops in the course of a few days with a clinical picture similar to so-called acute tubular, acute tubulo-interstitial, or acute interstital nephritis with allergic symptoms, such as rash, fever, eosinophilia and acute renal failure. In most patients the disease develops more insidiously with heavy proteinuria, a slowly worsening of the kidney function and a rising blood pressure. A microscopic investigation of a kidney biopsy specimen may in some patients reveal almost normal glomeruli as in so-called minimal change nephropathy. Other patients may have more or less pronounced depositions of immune components in the glomeruli in a pattern similar to membranous glomerulonephritis. In a few patients other glomerulonephritis subgroups are seen. Almost all patients have tubular, interstitial or tubulointerstitial changes.
As mentioned, NSAID nephropathy may often be followed by a reduced kidney function and the disease may progress to end-stage renal failure unless NSAID treatment is discontinued. If so, almost all patients recover, most of them with normal renal function.
The various clinical and laboratory appearances of NSAID nephropathy has led to the idea that the mechanisms behind them also vary. However, in an analysis of 97 case histories published in medical journals a pattern emerged that was suggestive of a common allergic mechanism (Ravnskov 1999). As the findings may have importance for an understanding of the mechanisms behind glomerulonephritis in general I shall shortly recapitulate them.
Three main groups of nephritis were recorded, 19 patients with acute tubular, interstitial or tubulointerstitial nephritis (to be short grouped together as “acute nephritis” in the following), 38 patients with minimal change nephropathy and 19 patients with membranous glomerulonephritis. A few other types were seen also, but they were too few to allow a systematic analysis.
It appeared that signs and symptoms of allergy were found in all the three main variants, most often in patients with acute NSAID nephropathy, least often in patients with membranous glomerulonephritis.
It was also obvious that the NSAID treatment time before the start of the disease differed substantially. Patients with acute nephritis had taken NSAID for on average 1.7 months, patients with minimal change nephropathy for on average 8.2 months, and patients with membranous glomerulonephritis for on average 39 months.
As is typical for most cases of acute nephritis due to other causes proteinuria was least pronounced in the acute NSAID nephritis, whereas heavy proteinuria was prevalent in the two other varieties, most pronounced in patients with minimal change nephropathy. In fact, the degree of proteinuria was independent on the amount of immune deposits in the glomeruli, in accordance with what I mentioned in the section Immunofluorescence Microscopy.
A typical finding on a kidney biopsy from patients with glomerulonephritis and heavy proteinuria is swelling and fusion of the podocytes, the glomerular epithelial cells. In accordance, such changes were found in all of the patients with minimal change nephropathy and membranous glomerulonephritis, but patients with acute NSAID nephritis had podocyte fusion also, although to a lesser degree, in support of a common mechanism behind all three types of NSAID nephropathy.
The general finding of podocyte swelling is suggestive of an allergic reaction involving activation of lymphocytes. It is well-known that activated lymphocytes may produce chemical substances, so-called lymphokines, that increase the permeability of the glomerular filters. Little attention has been raised to the fact that fusion of the podocytes is seen in most cases of acute nephritis due to other drugs also, although to a lesser degree than in glomerulonephritis, possibly because there is a time lag before the production of lymphokines is maximal (Ravnskov 1999).
Most important was that the renal function in NSAID nephropathy was strongly associated with the tubulointerstitial changes and strongly inversely associated with the amount of immune deposits in the glomeruli. The logical interpretation of this finding is of course that the primary damage is located to the tubulointerstitial tissue and that the glomerular changes are secondary and without importance for renal function. If the reaction against the NSAID is violent, the course is more dramatic and renal failure is prevalent, but with a short course, few if any immune components are deposited in the glomerular filters. With a milder and more protracted cause, time will allow more macromolecules to be caught in the glomeruli.
A relevant question: In most patients with acute nephritis due to an allergic reaction to a drug the kidney disease appears abruptly and the course is rapid and violent. If NSAID nephropathy is the result of an allergic reaction also, why is the course generally much more slow and why are the typical allergic symptoms absent in many patients, in particular those with a protracted course of the disease? The explanation may be that NSAIDs inhibit a variety of immunologic reactions, the very effect that has made these drugs suitable for treatment of inflammatory diseases. Most probably the milder course in NSAID nephropathy compared with acute nephritis induced by other drugs is due to a delay of the immunologic reactions induced by the offending NSAID itself causing the immune system to work ineffectively and in slow motion.
In conclusion, it is suggested that the various kidney diseases seen after NSAID treatment are not separate entities, but varying results of a common mechanism, an allergic reaction to the drug. In case the allergic reaction is strong and the effects of the offending drug on the immune system are weak, the patient will present with acute tubular, interstitial or tubulointerstitial nephritis. In case the allergic reaction is moderate, time will allow the lymphocytes that participate in the allergic reaction to produce lymphokines with unfavourable effects on the podocytes leading to heavy proteinuria. In case the allergic reaction is weak or the effects of the offending NSAID on the immune system is strong, the course will be even more protracted and as a result immune complexes, present in the blood circulation now and then, even in healthy individuals, will be caught in the glomeruli. The immune deposits are not causing the disease, they are secondary to the glomerular damage that is produced by the allergic reactions in the body.
Are allergic mechanisms participating also in glomerulonephritis associated with exposure to toxic chemicals? This is suggestive from one of the animal experiments. By exposing mice to carbon tetrachloride the researchers induced a mesangial glomerulonephritis with deposition of IgG in the glomeruli. However, if the mice were irradiated before the exposure no glomerulonephritis was seen (98). As the cells of the immunological system are particularly sensitive to irradiation this finding suggests that allergic reactions may be crucial, at least in glomerulonephritis induced by carbontetrachloride. Again you may ask, why is the course in most patients with glomerulonephritis much more protracted than in acute allergic, tubulointerrstitial nephritis? The same answer is valid. Almost all chemicals that have been associated with glomerulonephritis are toxic both to the kidneys’ tubules and to the body’s immune system (Ravnskov 1985).
To-day at least 60 case histories of glomerulonephritis associated with exposure to silicon have been published. Silicon is an element the salts of which, named silicates, are the main components in rocks and sand. Exposure to silicates is prevalent among miners, foundry and quarry workers, sandblasters, tile setters, glaziers, and workers in the production and handling of asbestos, mineral wool and fiber glass. The type of renal disease seen in such individuals is most often so-called focal, segmental glomerulonephritis, and a characteristic feature is the simultaneous presence of an auto-immune disease such as Wegener granulomatosis or systemic lupus erythematosus.
Case reports are weak evidence, because the association could occur by chance. However, there is also epidemiological evidence, that silicon or silicon salts may produce serious glomerulonephritis.
Cross-sectional studies of workers with occupational exposure to silicon compounds have shown that some of them may have urinary findings typical for early glomerulonephritis (107-109), even after a short exposure (110). After many years the exposure may result in serious kidney damage. In a cohort study of 2412 men who had worked on average eight years in a South Dakota gold mine between 1940 and 1965 the incidence of end-stage renal failure in 1977 was significantly higher than in the general population; in particular end-stage renal failure due to glomerulonephritis (111). In a review of 583 reported cases of silicosis (a serious lung disease caused by chronic inhalation of silicates) in Michigan between 1985 and 1995 a reduction of renal function was found in about a third of them (112).
Case control studies are also in support. In one such study of 272 patients with chronic renal failure and 272 people with normal renal function, 52 (19%) of the patients had been exposed to silicon-containing compounds but only 24 (8.8%) of the control individuals. Among the various diagnostic groups 16% of 38 patients with glomerulonephritis, and 26% of 39 patients with diabetic nephropathy had been exposed (113). In another case-control study fourteen of sixteen patients with glomerulonephritis and Wegener granulomatosis had been exposed to nephrotoxic chemicals, most of them to silica and silicon-containing compounds (113).
As is the case with almost all other chemicals associated with glomerulonephritis, chemicals derived from silicon are known for having disturbing effects on the immune system, in particular it has been found that autoimmunity is a common finding, seen both in exposed workers, and in experimental animals (114,115).
Thus, although studies of silicon-associated glomerulonephritis are much fewer, these studies suggest that exposure to silicon may also lead to end-stage glomerulonephritis.
In many countries diabetic nephropathy has become the most common cause of end-stage renal failure. It is a common belief that the complications to diabetes, including renal disease, is due to maltreatment of the diabetic condition. However, many studies have shown that this is only part of the truth, because many patients develop severe diabetic complications in spite of a meticulous control of the blood glucose level, and most diabetic patients survive for many years with a normal kidney function in spite of a badly controlled diabetes.
Other factors obviousoly contribute to the development of kidney disease in diabetic patients. One factor may be exposure to toxic chemicals because what has been said about glomerulonephritis in the previous sections seems to be valid for diabetic nephropathy also. This appears from two recent case-control studies.
In one of the studies 113 patients with juvenile diabetes for at least ten years were asked for hydrocarbon exposure since the diagnosis of diabetes had been settled. The exposure was minimal in a group of 45 patients without signs of kidney disease. In a group of 37 patients with microalbuminuria, the mildest form of diabetic kidney disease, and in a group of 31 patients with established nephropathy the exposure was significantly higher than in the first group, most pronounced in the group with overt kidney disease. Those with significant exposure had mainly been exposed to petroleum products, greasing and degreasing agents, paints and glues (116).
Another study included 39 patients with diabetic nephropathy and chronic renal failure. Compared with healthy control individuals the diabetic patients had been more often exposed to a variety of chemicals, including lead (28% exposed against 9.9% of the control individuals), welding fumes (18% against 7%), silicon-containing compounds (26% against 8.8%), chromium (23% against 3.7%) and hydrocarbons (39% against 25.7%) (117).
As seen from the preceding sections all six predictions have been fulfilled. In addition, almost all clinical and experimental observations are in better accordance with the toxic-allergic hypothesis than with the classical, immunological concept.
|The Predictions||The Evidence|
|1st prediction||Workers exposed to nephrotoxic chemicals should more often have symptoms of glomerulonephritis than other people.||In 14 cross-sectional studies of workers exposed to hydrocarbons and in four studies of workers exposed to silicon compounds, the exposed workers had more often symptoms of glomerulonephritis than had the unexposed control individuals.|
|2nd prediction||Patients with glomerulonephritis should have been exposed more often to nephrotoxic chemicals than other people.||All case-control studies that included patients with chronic or end-stage renal failure found significantly more exposure in patients compared with control individuals of the same sex and age. A strong, inverse association was found between renal function and degree of exposure.|
|3rd prediction||Patients with glomerulonephritis and a decreased renal function should have been exposed more often than patients with glomerulonephritis and normal function.|
|4th prediction||Discontinuation of the exposure should improve renal function and the course of the disease.||In the four studies, that had addressed this question, renal function worsened mainly or exclusively in patients who continued their exposure to hydrocarbons|
|5th prediction||The renal function and the course should be closer associated with the tubulointerstitial changes than with the glomerular changes.||Numerous studies have shown that the course and the renal function is strongly associated with the degree of tubulointerstitial damage but only weakly, if at all, by the degree of glomerular damage|
|6th prediction||Exposure of laboratory animals to nephrotoxic chemicals should produce glomerulonephritis with renal failure.||In 14 experimental studies most of the human glomerulonephritis subgroups have been produced by a variety of hydrocarbons. Also gold, lithium and mercury have produced glomerulonephritis in experimental animals (not yet reviewed here)|
You may probably ask why so little has been done to treat and prevent renal failure in patients who are exposed to toxic chemicals. How come that most nephrologists consider the problem of minor importance?
There are several answers. Most important is probably that patients with glomerulonephritis and other kidney diseases are not questioned professionally. Many doctors are not familiar with the working conditions of their patients, and many patients are unaware of their exposure. Therefore the doctor get the impression that heavy, toxic exposure is unusual, in particular if mainly patients with normal renal function are questioned.
However, it is a striking fact that more than 50 per cent of patients with glomeruloinephritis and end-stage renal failure have had prolonged and heavy exposure to nephrotoxic chemicals, in particular to organic solvents, fuels and motor exhausts. But to detect such exposure it is necessary to co-operate with experts in occupational medicine, as has been the case in almost all the scientific studies that I have referred to in the preceeding sections. Many times I have seen that even heavy and prolonged exposure may remain undetected unless the patient is interviewed by someone who is familiar with the working conditions in the trade and industry.
Therefore, if you suffer from glomerulonephritis, diabetic kidney disease or a kidney disease of unknown origin, in particular if your kidney function is reduced and if you think you may be exposed to toxic chemicals:
Ask your doctor to read this website. Many nephrologists are unfamiliar with the subject, or they have been told that the association between toxic exposure and glomerulonephritis is non-existing or of little importance.
Become a member of a patient association and inform the board about this website. Here are some:
US: The Patient & Family Council of the National Kidney Foundation
American Association of Kidney Patients
National Organization for Renal Disease
Canada: The Kidney Foundation of Canada
Sweden: Riksförbundet för njursjuka
|Acute interstitial nephritis
|A kidney disease characterized by acute onset, a decreased renal function and microscopic changes mainly located to the renal interstitium (edema and/or infiltration of white blood cells).|
|Acute tubular nephritis
|A kidney disease characterized by acute onset, a decreased renal function and microscopic changes mainly located to the renal tubules.|
|Acute tubulo-interstitial nephritis (ATIN)||A kidney disease characterized by acute onset, a decreased renal function and microscopic changes located to the tubules and the renal interstitium|
|Albumin||The dominating protein in the plasma. The normal level of albumin in the plasma of healthy individuals is about 4 gram per liter.|
|Antigen||A substance, foreign to the body, that stimulates the immune system to produce antibody or to elicit a response from white blood cells. The resulting antibodies and the reacting cells are specific for the stimulating antigen|
|Antibody||A plasma protein (immunoglobulin) that has the ability to combine with the antigen that caused its production (see above)|
|Atrioventricular shunt||A device for drainage of the cerebral ventricular fluid (“water on the brain”), for instance inoperated between the ventricles of the brain and the right atrium of the heart.|
|Auto-immune disease||A condition where the immune system reacts against the body’s own constituents|
|Casts||Cylindric formations in the urine produced by protein that has coagulated inside the renal tubules. Casts may contain various blood cells or tubular epithelial cells.|
|Complement||A complex system of more than 30 various enzymes in serum and on the surface of cells. They are activated for instance by contact with immune complexes and microorganisms. Being activated they will start various types of inflammatory reactions in the tissue and thus contribute to an elimination of microorganisms or damaged cells.|
|Electron microscope||With a (transmission) electron microscope it is possible to reveal the ultrastructure of the interior of cells. An electron microscope may enlarge by almost 500,000 times.|
|Eosinophilia||An increased number of a certain type of white blood cells, the eosinophilic leucocytes. An abnormally high number of eosinophils is a common finding in patients with an allergic disease.|
|Focal, segmental glomerulonephritis||Glomerulonephritis localized to a few glomeruli only (focal) and in these glomeruli only to segments of the glomerulus (segmental). One of the many unanswered questions about glomerulonephritis is how an immunological disease can be focal and segmental. The phenomenon is easily explained by the toxic-allergic hypothesis (Ravnskov 1988).|
|Glomerular basement membrane (GBM)||The membrane that separate the capillary walls in the glomerulus from the urinary space. The primary urine is produced by blood filtered through the GBM|
|A glomerulus is composed of 5-6 capillary loops that spring from the afferent arteriole (the arteriole that leds to the glomeruli) and end in the efferent arteriole (the arteriole that leads away from the glomerulus), surrounded by Bowman’s capsule. The wall of a glomerular capillary is composed of three layers, the endothelial cells that line the inside of the capillary wall, the glomerular basement membrane, and the glomerular epithelial cells (also named podocytes) that are continuous with the cells lining the inside of Bowman’s capsule which again are continuous with the tubular cells. Each kidney has about 1 million glomeruli.|
|Goodpasture’s syndrome||A rare disease characterized by anti-GBM nephritis and bleedings from the lungs|
|Haematuria||Blood in the urine|
|Hydrocarbon||A chemical compund the core of which is composed by carbon and hydrogen atoms. In an aliphatic hydrocarbon the carbon atoms are put together as a chain; in an aromatic hydrocarbon they are put together as a ring or as several rings (polyaromatic hydrocarbons). The most important sources of hydrocarbon exposure are mineral oil, petroleum distillates and combustion fumes. Most fuels and solvents are produced by distillation of mineral oil at different temperatures. As it is extremely difficult to isolate a pure hydrocarbon by distillation all hydrocarbon products are composed of hundreds or thousands of different hydrocarbon molecules.|
|Immune complex||The union of antigen, antibody and complement|
|Immunofluorescence microscopy||A technique used to localize specific constituents in tissue sections. Specific antibodies against the constituent in question are tagged with fluorescent chemicals. In the microscope it is thus possible to recognize the localization in the tissue of any constituent provided a specific antibody is available. In glomerulonephritis the technique is primarily used to identify various immunoglobulins and complement components in the glomeruli.|
|Immunoglobulin||A group of plasma proteins, produced by the immune system and functioning as antibodies. There are five types of immunoglobulins, immunoglobulin G (IgG), A (IgA), M (IgM), D (IgD) and E (IgE)|
|Inflammation||An influx into the tissue of blood cells and fluid caused by reactions of the immune system against injury or foreign substances, for instance microorganisms or chemicals.|
|Interstitium, renal||The connective tissue that binds together the glomeruli and the tubules|
|Lymphokine||A substance produced by lymphocytes (a kind of white blood cells) when the lymphocyte is stimulated by an antigen. Lymphokines are released to the blood circulation and they can thus exert their effect far away from the cells that produced it|
|Membranous glomerulonephritis||A subgroup of glomerulonephritis characterized by granular deposits of immunoglobulins and complement lying on the outside of the glomerular basement membrane beneath the epithelial cells. They have a typical appearance on electron microscopy. Membranous glomerulonephritis is thought to be caused by auto-immunity, eg. the antibodies áttack some of the body’s own components located in the glomerulus.|
|Minimal change nephropathy||A subgroup of glomerulonephritis characterized by heavy proteinuria but with no or minimal changes seen by light microscopy and no deposits of immunoglobulins or complement factors are seen by immunofluorescence microscopy. Electron microscopy shows fusion of the podocytes. Minimal change nephropathy is the most common type of glomerulonephritis in children and there is much evidence that the increased permeability of the glomerular filter and the resulting proteinuria and podocyte fusion is caused by lymphokines|
|Nephrotic syndrome||A combination of heavy proteinuria, low plasma albumin and fluid retention in the body.|
|Nephrotoxic||Toxic to the kidneys|
|Plasma||The fluid that remains when all cells of the blood (red and white blood cells and platelets) have been eliminated (by centrifugation).|
|Podocyte||Another name for the glomerular epithelial cell, see glomerulus|
|Primary urine||The fluid that is produced after filtration of the blood in the glomeruli. Almost 200 liter primary urine is produced by the glomeruli every 24 hour. After having passed the renal tubules this amount is reduced to 1-3 liter urine|
|Proteinuria||An increased amount of plasma proteins in the urine. Normal urine has less than 25 mg protein per liter. Urine from patients with the nephrotic syndrome has 4 gram protein per liter or more|
|Systemic Lupus Erythematosus (SLE)||A chronic, autoimmune, inflammatory disease, most commonly affecting the skin, the joints (arthritis) and the kidneys (glomerulonephritis), but many other organs may be affected as well.|
|Serum||The fluid that remains when blood has coagulated and the clot has been removed, eg. serum is plasma without fibrinogen.|
|T-cell||A white blood cell produced in the thymus. T-cells have important functions in the body’s defense against microorgaanisms|
|Tubules||Microscopic channels that lead the primary urine through the kidney to the pelvis of the kidney from where it goes down to the urinary bladder. During the passage through the tubules, salt, water and other useful substances are reabsorped from the primary urine and toxic substances are excreted into it. The tubules also maintain the body’s acid-base balance.|
|Tubulointerstitial tissue||The tissue that surrounds the glomeruli, composed of the tubules (normally by far the major part) and the interstitial tissue. In inflammatory states the interstitial tissue is increased and may be dominated by white blood cells and/or edema and/or connective or fibrous tissue, a condition called interstitial nephritis. In case the tubules are abnormal also, it is called tubulointerstitial nephritis.|
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