Introduction
Each kidney contains about 1 million filtering units (glomeruli). The glomeruli are made up of many microscopic clusters of tiny blood vessels (capillaries) with small pores. These blood vessels are designed to leak fluid from the bloodstream into a system of miniature tubules that process the fluid to become urine. Normally this filtering system permits fluid and small molecules (but almost no protein or blood cells) to leak into the tubules. Diseases that affect the kidneys can be divided into three categories based on the way they affect different parts of the kidneys: With glomerulonephritis, the inflammation is often the result of an abnormal immune reaction. Such a reaction can occur in two ways: (1) Antibodies (proteins made by the body to attack specific molecules called antigens) may attach directly to cells of the kidney or molecules trapped in them, causing inflammation. (2) Antibodies attach to antigens outside the kidney, and these antigen-antibody (or immune) complexes are carried to the kidney by the bloodstream and get trapped in the glomeruli, causing inflammation. If enough glomeruli are damaged, kidney function is decreased. As a result, urine production falls and waste products build up in the blood. Also, when damage is severe, inflammatory cells and injured glomerular cells accumulate, compressing the capillaries within the glomerulus and interfering with filtration. Scarring may develop, which also impairs kidney function and reduces urine production. In some cases, tiny blood clots (microthrombi) may form in the small blood vessels, further decreasing kidney function. Rarely, glomerulonephritis can result from a hereditary condition. In other cases, glomerulonephritis is caused by inflammation of the blood vessels (vasculitis). Nephrotic syndrome causes large amounts of protein to leak from blood into the urine. This leakage can be caused by damage to the glomeruli by inflammatory or noninflammatory processes. In inflammatory processes, red blood cells appear in the urine. Nephrotic syndrome caused by inflammation therefore has characteristics similar to those of glomerulonephritis. With noninflammatory processes, no red blood cells appear in the urine. Some forms of nephrotic syndrome can be severe. The glomeruli become scarred, and kidney failure develops. In less severe forms of nephrotic syndrome, kidney function decreases very little. Tubulointerstitial nephritis often is caused by a toxic or allergic reaction to a drug. White blood cells or scar tissue appears in the kidney's tissues. Infection of the kidneys (pyelonephritis—see Urinary Tract Infections (UTI): Kidney Infection (Pyelonephritis)) can also cause tubulointerstitial nephritis. When inflammation damages the tubules and surrounding tissues, the kidneys may become unable to perform their normal functions, such as concentrating urine, eliminating (excreting) waste products from the body, or balancing the excretion of sodium and other electrolytes, such as potassium. If the damage is severe and affects both kidneys, the result is kidney failure.
Glomerulonephritis (Nephritic Syndrome)
Glomerulonephritis (nephritic syndrome) is a disorder of glomeruli (clusters of microscopic blood vessels in the kidneys with small pores through which blood is filtered). It is characterized by body tissue swelling (edema), high blood pressure, and the presence of red blood cells in the urine. Glomerulonephritis can develop over a short time period (acute glomerulonephritis) or develop and progress slowly (chronic glomerulonephritis). In 1% of children and 10% of adults who have acute glomerulonephritis, it evolves into rapidly progressive glomerulonephritis, in which most of the glomeruli are destroyed, resulting in kidney failure. Causes Glomerulonephritis can be primary, affecting only the kidneys, or secondary, caused by a vast array of disorders that affect other parts of the body. Acute Glomerulonephritis: Acute glomerulonephritis most often occurs as a complication of throat or skin infection by streptococcus, a type of bacteria. Acute glomerulonephritis that occurs after a streptococcal infection (post-streptococcal glomerulonephritis) typically develops in children between the ages of 2 and 10 following recovery from the infection. Infections with other types of bacteria, such as staphylococcus and pneumococcus, viral infections, such as chickenpox, and parasitic infections, such as malaria, can also result in acute glomerulonephritis. Acute glomerulonephritis that results from any of these infections is called postinfectious glomerulonephritis. Noninfectious causes of acute glomerulonephritis include membranoproliferative glomerulonephritis, immunoglobulin A (IgA) nephropathy, thin basement membrane disease, Henoch-Schönlein purpura, systemic lupus erythematosus (lupus), cryoglobulinemia, Goodpasture's syndrome, and Wegener's granulomatosis. Acute glomerulonephritis that develops into rapidly progressive glomerulonephritis most often results from conditions that involve an abnormal immune reaction. Chronic Glomerulonephritis: Often, chronic glomerulonephritis seems to result from one of the same conditions that cause acute glomerulonephritis, such as IgA nephropathy or membranoproliferative glomerulonephritis. Sometimes, acute glomerulonephritis does not resolve and instead becomes chronic. Occasionally, chronic glomerulonephritis is caused by hereditary nephritis, an inherited genetic disorder. In many people, the cause of chronic glomerulonephritis cannot be identified. Symptoms About half of the people with acute glomerulonephritis have no symptoms. If symptoms do occur, the first to appear are tissue swelling (edema) due to fluid retention, low urine volume, and production of urine that is dark because it contains blood. Edema may first appear as puffiness of the face and eyelids but later is prominent in the legs. Blood pressure increases as kidney function becomes impaired. In turn, high blood pressure and swelling of the brain may produce headaches, visual disturbances, and more serious disturbances of brain function (for example, seizures or coma). In older people, nonspecific symptoms, such as nausea and a general feeling of illness (malaise), are more common. When rapidly progressive glomerulonephritis develops, weakness, fatigue, and fever are the most frequent early symptoms. Loss of appetite, nausea, vomiting, abdominal pain, and joint pain are also common. About 50% of people have a flu-like illness in the month before kidney failure develops. These people have edema and usually produce very little urine. High blood pressure is uncommon and rarely severe when it does occur. Because chronic glomerulonephritis usually causes only very mild or subtle symptoms, it goes undetected for a long time in most people. Edema may occur. High blood pressure is common. The disease may progress to kidney failure, which can cause itchiness, fatigue, decreased appetite, nausea, vomiting, and difficulty breathing. Diagnosis Doctors investigate the possibility of acute glomerulonephritis in people whose laboratory test results indicate kidney dysfunction or blood in the urine and in people who develop symptoms of the disorder, particularly those who have had strep throat or other infections. Laboratory tests show variable amounts of protein and blood cells in the urine and often kidney dysfunction, as shown by a high concentration of urea and creatinine (waste products) in the blood. In people with rapidly progressive glomerulonephritis, casts (clumps of red blood cells or white blood cells) are almost always visible in a urine sample that is examined under a microscope. Blood tests detect anemia and often an abnormally high number of white blood cells. When doctors suspect glomerulonephritis, a biopsy of the kidney is usually done to confirm the diagnosis, help determine the cause, and determine the amount of scarring and potential for reversibility. Kidney biopsy is done by inserting a needle in one of the kidneys under ultrasound or computed tomography (CT) guidance to obtain a small amount of kidney tissue. Although kidney biopsy is an invasive procedure and occasionally can become complicated, it is usually safe. Additional tests are sometimes helpful for identifying the cause. For example, a throat culture may provide evidence of streptococcal infection. Blood levels of antibodies against streptococci may be higher than normal or progressively increase over several weeks. Acute glomerulonephritis that follows an infection other than strep throat is usually easier to diagnose, because its symptoms often begin while the infection is still obvious. Cultures and blood tests that help identify the organisms that cause these other types of infections are sometimes needed to confirm the diagnosis. Chronic glomerulonephritis develops gradually, and therefore, a doctor may not be able to tell exactly when it began. It may be discovered when a urine test, done as part of a medical examination, reveals the presence of protein and blood cells in a person who is feeling well, has normal kidney function, and has no symptoms. Doctors usually do an imaging test of the kidneys, such as an ultrasound, CT scan, or magnetic resonance imaging (MRI) scan. A kidney biopsy is the most reliable way to distinguish chronic glomerulonephritis from other kidney diseases. A biopsy, however, is rarely done in advanced stages. In these cases, the kidneys are shrunken and scarred, and the chance of obtaining specific information about the cause is small. Doctors suspect that the kidneys are shrunken and scarred if kidney function has been poor for a long time and the kidneys appear abnormally small on an imaging test. Prognosis Acute poststreptococcal glomerulonephritis resolves completely in most cases, especially in children. About 0.1% of children and 25% of adults develop chronic kidney failure. The prognosis for people with rapidly progressive glomerulonephritis depends on the severity of glomerular scarring and whether the underlying disease, such as infection, can be cured. In about 75% of the people who are treated early (within weeks to a few months), kidney function is preserved and dialysis is not needed. However, because the early symptoms can be subtle and vague, many people who have rapidly progressive glomerulonephritis are not aware of the underlying disease and do not seek medical care until kidney failure develops. If treatment occurs late, the person is more likely to develop chronic kidney failure. The prognosis also depends on the cause, the person's age, and any other diseases the person might have. When the cause is unknown or the person is older, the prognosis is worse. In some children and adults who do not recover completely from acute glomerulonephritis, other types of kidney disorders develop, such as asymptomatic proteinuria and hematuria syndrome or nephrotic syndrome. Other people with acute glomerulonephritis, especially older adults, often develop chronic glomerulonephritis.
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| Primary Glomerular Disorders That Can Cause Glomerulonephritis |
Disorder | Description | Prognosis |
Fibrillary glomerulonephritis | A rare disease in which abnormal proteins are deposited around the glomerulus; it may also cause nephrotic syndrome | The prognosis is poor; end-stage kidney failure occurs in half of people within 4 years. It is not clear how much treatment (with corticosteroids and immunosuppressants) helps |
Primary rapidly progressive glomerulonephritis | A group of disorders that cause microscopic damage to the glomeruli and progress rapidly; sometimes they are caused by an infection or other treatable disorder | The prognosis is poor; at least 80% of people develop end-stage kidney failure within 6 months without treatment. The prognosis is better for people younger than 60 years or if an underlying disorder causing the glomerulonephritis responds to treatment |
Immunoglobulin A (IgA) nephropathy | The most common form of glomerulonephritis in the world; caused by immune complexes (combinations of antigens and antibodies) deposited in the kidney | Usually the disorder progresses slowly; end-stage kidney failure develops in about 20% to 40% of people after 5 to 25 years; progresses more slowly in children |
Thin basement membrane disease (benign familial hematuria) | A hereditary disorder caused by thinning of a part of the glomerulus called the basement membrane | The prognosis is excellent; most people do not develop end-stage kidney failure |
Membranoproliferative glomerulonephritis | An uncommon type of glomerulonephritis primarily occurring between the ages of 8 and 30; sometimes the cause is unknown, or the disorder may be caused by immune complexes (combinations of antigens and antibodies) attaching to the kidney | If caused by immune complex disease, a partial remission may occur; the outcome is not as good in people in whom the cause remains unknown. About half of untreated people will progress to end-stage kidney failure within 10 to 15 years, while in most others the kidney function stabilizes or improves |
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Treatment No specific treatment is available in most cases of acute glomerulonephritis. Following a diet that is low in protein and sodium may be necessary until kidney function recovers. Diuretics may be prescribed to help the kidneys excrete excess sodium and water. High blood pressure needs to be treated. When a bacterial infection is suspected as the cause of acute glomerulonephritis, antibiotics are usually ineffective because the nephritis begins 1 to 6 weeks (average, 2 weeks) after the infection, which has, by then, usually resolved. However, if a bacterial infection is still present when acute glomerulonephritis is discovered, antibiotic therapy is started. Antimalarial drugs may be beneficial if the cause of the syndrome is malaria. For rapidly progressive glomerulonephritis, drugs to suppress the immune system are started promptly. High doses of corticosteroids are usually given intravenously for about a week, followed by a variable period of time when they are taken by mouth. Cyclophosphamide , an immunosuppressant, may also be given. In addition, plasmapheresis is sometimes used to remove antibodies from the blood. The sooner treatment occurs, the less likely are kidney failure and the need for dialysis. Kidney transplantation is sometimes considered for people who develop chronic kidney failure, but rapidly progressive glomerulonephritis may recur in the transplanted kidney. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) either alone or in combination often slow progression of chronic glomerulonephritis. Taking drugs to reduce high blood pressure and reducing sodium intake are considered beneficial. Restricting the amount of protein in the diet is modestly helpful in reducing the rate of kidney deterioration. End-stage kidney failure can be treated with dialysis or a kidney transplant. ASYMPTOMATIC PROTEINURIA AND HEMATURIA SYNDROME Asymptomatic proteinuria and hematuria is the result of diseases of glomeruli (clusters of microscopic blood vessels in the kidneys that have small pores through which blood is filtered) characterized by steady or intermittent loss of small amounts of protein and blood in the urine. Small amounts of protein excreted in the urine (proteinuria) or blood excreted in the urine (hematuria) are sometimes discovered in people without symptoms, when urine tests are done for some routine purpose. The presence of casts (clumps of red blood cells) or abnormally shaped red blood cells is a clue for doctors that the blood in the urine came from glomeruli. Casts and proteinuria may be present because the person is recovering from a recent undiagnosed episode of nephritis. If this situation seems likely, a doctor needs only to recheck the person over the next weeks or months to make sure that the abnormalities resolve. If casts and proteinuria persist, the cause is usually one of three disorders. One is immunoglobulin A (IgA) nephropathy, a type of nephritis caused by deposition of immune complexes (combinations of antibodies and antigens) in the kidney that can be very mild and nonprogressive or become a severe disease leading to kidney failure. Another is hereditary nephritis (Alport's syndrome), a progressive disorder that can be severe and lead to kidney failure. The third disorder is thin basement membrane disease (benign familial hematuria). Thin basement membrane disease is a hereditary disorder caused by thinning of a part of the glomerulus called the basement membrane. It follows a mild and nonprogressive course. The diagnosis can usually be made with a kidney biopsy. However, a kidney biopsy is rarely done because the likelihood of finding a treatable disease is very low. Doctors usually recommend that people with asymptomatic proteinuria and hematuria have a physical examination and undergo urine testing once or twice a year. Additional tests are done if the amount of protein or blood increases much, or if symptoms occur that suggest the development of a specific disease. Most people with asymptomatic proteinuria and hematuria syndrome do not worsen, and the condition may persist indefinitely. HEREDITARY NEPHRITIS (ALPORT'S SYNDROME) Hereditary nephritis (Alport's syndrome) is a genetic disorder in which kidney function is poor, blood is present in the urine, and deafness and eye abnormalities sometimes occur. Hereditary nephritis is usually caused by a defective gene on the X chromosome, but it sometimes results from an abnormal gene on a nonsex (autosomal) chromosome. Other factors influence how severe the disorder is in a person who has the gene. Females with the defective gene on one of their two X chromosomes usually do not have symptoms, although their kidneys may function somewhat less efficiently than normal. Most of these females have some blood in the urine. Males with the defective gene develop more severe problems because males do not have a second X chromosome to compensate for the defect. Males usually develop kidney failure between the ages of 20 and 30. Many people with the defective gene on only one autosomal chromosome have no symptoms other than blood in the urine, but the urine may also contain varying amounts of protein, white blood cells, and casts (small clumps of cells) that are visible under a microscope. Kidney function in people who have the defective gene on two autosomal chromosomes slowly worsens, and kidney failure usually occurs. Hereditary nephritis can affect other organs. Hearing problems, usually an inability to hear sounds in the higher frequencies, are common. Cataracts can also occur, although less often than hearing loss. Abnormalities of the cornea, lens, or retina sometimes cause blindness. Other problems include a low number of platelets in the blood (thrombocytopenia) and abnormalities that affect several nerves (polyneuropathy). People who develop kidney failure need to undergo dialysis or receive a kidney transplant. Genetic testing is usually offered to people who want to have children. NAIL-PATELLA SYNDROME The nail-patella syndrome (also called osteo-onychodysplasia, arthro-onychodysplasia, and onycho-osteodysplasia) is a rare hereditary disorder that results in abnormalities of the kidneys, bones, joints, and fingernails. The gene that causes nail-patella syndrome is dominant. Commonly, people who have this syndrome have one or both kneecaps (patellas) missing, one of the arm bones (the radius) dislocated at the elbow, and the pelvic bone abnormally shaped. They have either no fingernails or poorly developed ones, with pitting and ridges. About 30% to 40% of people with this syndrome have blood or protein in their urine, which may prompt the doctor to order kidney function tests. Kidney failure eventually develops in about 30% of the people with affected kidneys by the time they are 50 or 60. The diagnosis is confirmed by bone x-rays and a biopsy of kidney tissue. There is no effective treatment for this syndrome. Controlling blood pressure may slow the rate of deterioration of kidney function. Those who develop kidney failure need dialysis or a kidney transplant. Genetic testing is usually offered to people who want to have children.
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Nephrotic Syndrome
Nephrotic syndrome is a disorder of the glomeruli (clusters of microscopic blood vessels in the kidneys that have small pores through which blood is filtered) in which excessive amounts of protein are excreted in the urine. This typically leads to accumulation of fluid in the body (edema) and low levels of the protein albumin and high levels of fats in the blood. Nephrotic syndrome can develop gradually or suddenly. Nephrotic syndrome can occur at any age. In children, it is most common between the ages of 18 months and 4 years, and more boys than girls are affected. In older people, both sexes are equally affected. Protein excretion into the urine (proteinuria) is accompanied by low levels of important proteins, such as albumin, in the blood, increased levels of fats (lipids) in the blood, a tendency for increased blood clotting, and a greater susceptibility to infection. The decreased level of albumin in the blood leads to edema and to the retention of excess sodium. Causes Nephrotic syndrome can be primary, affecting only the kidneys, or secondary, caused by a vast array of disorders that affect other parts of the body, most commonly diabetes mellitus, systemic lupus erythematosus, and certain viral infections. Nephrotic syndrome can also result from glomerulonephritis. A number of drugs that are toxic to the kidneys can also cause nephrotic syndrome, especially nonsteroidal anti-inflammatory drugs (NSAIDs). The syndrome may be caused by certain allergies, including allergies to insect bites and to poison ivy or poison oak. Some types of nephrotic syndrome are hereditary.
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* Asterisks indicate the most common causes. |
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Symptoms Early symptoms include loss of appetite, a general feeling of illness (malaise), puffy eyelids and tissue swelling from excess sodium and water retention, abdominal pain, wasting of muscles (atrophy), and frothy urine. The abdomen may be swollen because of a large accumulation of fluid in the abdominal cavity (ascites). Shortness of breath may develop because fluid accumulates in the space surrounding the lungs (pleural effusion). Other symptoms may include swelling of the knees and, in men, the scrotum. Most often, the fluid that causes tissue swelling is affected by gravity and therefore moves around. During the night, fluid accumulates in the upper parts of the body, such as the eyelids. During the day, when the person is sitting or standing, fluid accumulates in the lower parts of the body, such as the ankles. Swelling may hide the muscle wasting that is progressing at the same time. In children, blood pressure is generally low, and blood pressure may fall when the child stands up (orthostatic hypotension). Shock occasionally develops. Adults may have low, normal, or high blood pressure. Urine production may decrease, and kidney failure may develop if the leakage of fluid from blood vessels into tissues depletes the liquid component of blood and the blood supply to the kidney is diminished. Occasionally, kidney failure with low urine output occurs suddenly. Nutritional deficiencies may result because nutrients are excreted in the urine. In children, growth may be stunted. Calcium may be lost from bones. The hair and nails may become brittle, and some hair may fall out. Horizontal white lines may develop in fingernail beds for unknown reasons. The membrane that lines the abdominal cavity and abdominal organs (peritoneum) may become inflamed and infected. Opportunistic infections—infections caused by normally harmless bacteria—are common. The higher likelihood of infection is thought to occur because the antibodies that normally combat infections are excreted in the urine or not produced in normal amounts. The tendency for blood clotting (thrombosis) increases, particularly inside the main vein from the kidney. Less commonly, the blood may not clot when clotting is needed, generally leading to excessive bleeding. High blood pressure accompanied by complications affecting the heart and brain is most likely to occur in people who have diabetes or systemic lupus erythematosus. Diagnosis A doctor bases the diagnosis of nephrotic syndrome on the symptoms, physical examination findings, and laboratory findings. Sometimes nephrotic syndrome is at first mistaken for heart failure in older adults because swelling occurs in both disorders and heart failure is common in older people. A laboratory test of urine collected over a 24-hour period is useful for measuring the degree of protein loss, but collection of urine over such a long period is difficult for many people to accomplish. Alternatively, to estimate protein loss, a randomly collected urine specimen can be tested to measure the ratio of the level of protein to that of creatinine (a waste product). Blood tests and other urine tests detect additional characteristics of the syndrome. The level of albumin in the blood is low because this vital protein is excreted in the urine and its production is impaired. The urine often contains clumps of cells that may be combined with protein and fat (casts). The urine contains low levels of sodium and high levels of potassium. Concentrations of lipid in the blood are high, sometimes exceeding 10 times that of a normal concentration. Levels of lipid in the urine are also high. Anemia may be present. Levels of blood clotting proteins may be increased or decreased. The doctor investigates possible causes of nephrotic syndrome, including drugs. Analysis of the urine and blood may reveal an underlying disorder. An imaging test of the kidney, such as ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI), is usually done. If the person has lost weight or is older, a search for cancer is undertaken. A kidney biopsy is especially useful in determining the cause and extent of kidney damage. Prognosis The prognosis varies depending on the cause of the nephrotic syndrome, the person's age, and the type and degree of kidney damage. Symptoms may disappear completely if the nephrotic syndrome is caused by a treatable disorder, such as an infection, cancer, or drugs. This situation occurs in about half the cases in children but less often in adults. If the underlying disorder responds to corticosteroids, sometimes progression of the disease is halted, and less often the condition partially or, rarely, completely reverses. When the syndrome is caused by HIV infection, it usually progresses relentlessly, often resulting in complete kidney failure in 3 or 4 months. Children born with the nephrotic syndrome rarely live beyond their first birthday, although a few have survived by means of dialysis treatments or a kidney transplant. When the cause is systemic lupus erythematosus or diabetes mellitus, drug treatment often stabilizes or decreases the amount of protein in the urine. However, some people do not respond to drug treatment and develop progressive kidney failure within a few years. In cases of nephrotic syndrome resulting from conditions such as an infection, allergy, or intravenous heroin use, the prognosis varies, depending on how early and effectively the underlying condition is treated.
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| Primary Glomerular Disorders That Can Cause Nephrotic Syndrome |
Glomerular Disorder | Description | Prognosis |
Minimal change disease | A mild disease of the glomerulus that is more common in children but also affects adults | The prognosis is good; 90% of children and nearly as many adults respond to treatment. In 30 to 50% of adults, disease relapses. After treatment for 1 or 2 years, more than 80% of people have permanent remission |
Focal segmental glomerulosclerosis | A disease that damages glomeruli; it affects mainly adolescents but also young and middle-aged adults; it is more common in blacks | The prognosis is poor because treatment is not very effective. In most adults and children, the disease progresses to end-stage kidney failure 5 to 20 years after being diagnosed |
Membranous glomerulopathy | A serious type of glomerular disease, affecting mainly adults; it is more common in whites | Spontaneous remission of proteinuria occurs in 30 to 40% of people. The likelihood of end-stage kidney failure rises steadily over time to about 40% at 15 years |
Congenital and infantile nephrotic syndrome | A rare inherited disease; congenital nephrotic syndrome (Finnish type) and diffuse mesangial sclerosis are the two main causes; they closely resemble focal segmental glomerulosclerosis; symptoms are present at birth in the Finnish type and develop during childhood in the infantile variety | The disorder does not respond to corticosteroids. Because the level of albumin in the blood is extremely low, removal of both kidneys is often considered. Supportive therapy, including dialysis, is given until the child is eligible for a kidney transplant |
Membranoproliferative glomerulonephritis | An uncommon type of glomerulonephritis, it primarily occurs between the ages of 8 and 30; sometimes the cause is unknown, or it may be caused by immune complex disease, which is caused by immune complexes (combinations of antigens and antibodies) attaching to the kidney | If caused by immune complex disease, a partial remission may occur; the outcome is not as good in people in whom the cause remains unknown. About half of untreated people will progress to end-stage kidney failure within 10 to 15 years, while in most others kidney function stabilizes or improves |
Mesangial proliferative glomerulonephritis | Accounts for about 3 to 5% of people with nephrotic syndrome of unknown cause; affects all ages; sometimes considered a subtype of membranoproliferative glomerulonephritis; may be a severe form of minimal change disease | About 50% of people initially respond to corticosteroids; 10 to 30% develop progressive kidney failure, relapses may respond to cyclophosphamide |
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Prevention and Treatment Use of an angiotensin-converting enzyme (ACE) inhibitor, such as enalapril , quinapril, or lisinopril , or an angiotensin II receptor blocker (ARB), such as candesartan , losartan , or valsartan , alone or in combination is the mainstay of both prevention and treatment. When a person with a disease such as systemic lupus erythematosus or diabetes mellitus has mild or moderate proteinuria, an ACE inhibitor or ARB is used as soon as possible because it may prevent proteinuria from increasing and kidney function from worsening. When a person who already has nephrotic syndrome is treated with an ACE inhibitor or ARB, symptoms may improve, the amount of protein excreted in the urine usually decreases, and lipid concentrations in the blood are likely to decline. However, these drugs can increase the potassium levels in the blood in people who have moderate to severe kidney failure, which can cause potentially dangerous heart rhythm abnormalities. General therapy for nephrotic syndrome includes a diet that contains normal amounts of protein and potassium but that is low in saturated fat and cholesterol and sodium. Some doctors recommend limiting the amount of protein in the diet. If fluid accumulates in the abdomen, the person may need to eat frequent, small meals because of the reduced capacity of the stomach. High blood pressure is usually treated with diuretics. Diuretics can also reduce fluid retention and tissue swelling but may increase the risk of blood clots. Anticoagulants may help control clot formation if it occurs. Infections can be life threatening and must be treated promptly. Whenever possible, specific treatment is aimed at the cause. Treating an infection that causes nephrotic syndrome may cure the syndrome. If a treatable disease, such as certain cancers, causes the syndrome, treating that disease can eliminate the syndrome. If a heroin user with the nephrotic syndrome stops using heroin in the early stages of the disease, the syndrome may resolve. If other drugs are responsible for the syndrome, discontinuing the drugs may be curative. People who are sensitive or allergic to poison oak, poison ivy, or insect bites should avoid these irritants.If no reversible cause can be found, the person may be given corticosteroids and other drugs that suppress the immune system, such as cyclophosphamide . However, corticosteroids cause problems, particularly for children, in whom these drugs can stunt growth and suppress sexual development (see Joint Disorders: Corticosteroids: Uses and Side Effects ).
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Tubulointerstitial Nephritis
Tubulointerstitial nephritis is inflammation that affects the tubules of the kidneys and the tissues that surround them (interstitial tissue). Tubulointerstitial nephritis may be acute or chronic, and it often results in kidney failure. It may be caused by various diseases, drugs, toxins, or radiation that damages the kidneys. Damage to the tubules results in changes in the concentrations of electrolytes in the blood or in problems with the kidney's ability to concentrate urine. There are two parts of the kidney tubules, the proximal and the distal. When the proximal tubule is damaged, the normal reabsorption into the blood of sodium, potassium, bicarbonate, uric acid, and phosphate may be altered, resulting in low levels in the blood of these substances. Injuries to the distal tubule are usually associated with a loss of urine-concentrating ability and an increase in daily urine volume (polyuria). Causes The most common cause of acute tubulointerstitial nephritis is an allergic reaction to a drug. Antibiotics such as penicillin and the sulfonamides, diuretics, and nonsteroidal anti-inflammatory drugs (NSAIDs)—including aspirin —may trigger an allergic reaction. The interval between the exposure to the allergen that caused the reaction and the development of acute tubulointerstitial nephritis varies from 5 days to 5 weeks. Drugs can also cause tubulointerstitial nephritis through nonallergic mechanisms. For example, NSAIDs can damage the tissues gradually, taking up to 18 months to cause chronic tubulointerstitial nephritis. Infection of the kidneys (pyelonephritis) can also cause acute or chronic tubulointerstitial nephritis. Kidney failure is unlikely unless inflammation causes a blockage in the urinary tract or pyelonephritis occurs in both kidneys. Symptoms and Diagnosis Some people have few or no symptoms. When symptoms develop, they are highly variable, and they may develop suddenly or gradually. When tubulointerstitial nephritis develops suddenly, the amount of urine produced may be normal or less than normal. Some people develop the symptoms of pyelonephritis: fever, painful urination, pus in the urine, and pain in the lower back or side (flank). If the cause is an allergic reaction, symptoms may include fever and a rash. When tubulointerstitial nephritis develops gradually, the first symptoms to appear are those of kidney failure, such as itchiness, fatigue, decreased appetite, nausea, vomiting, and difficulty breathing. Blood pressure is normal or only slightly above normal in the early stages of the disease. The amount of urine produced may be greater than normal. Laboratory tests usually detect signs of kidney failure, such as an increase in the level of waste products in the blood, or other characteristic abnormalities, such as metabolic acidosis, hypokalemia, hypouricemia, or hypophosphatemia. A kidney biopsy is the only conclusive means of diagnosing tubulointerstitial nephritis, although a biopsy is rarely done except when the cause cannot be found or treatment with corticosteroids is being considered. When tubulointerstitial nephritis develops suddenly, the urine may be almost normal, with only a trace of protein or pus, but often the abnormalities are striking. The urine may show large numbers of white blood cells, including eosinophils. Eosinophils rarely appear in the urine, but when they do, a person usually has acute tubulointerstitial nephritis caused by an allergic reaction. Also, the number of eosinophils in the blood may be increased. When an allergic reaction is the cause, the kidneys usually are large because of inflammation caused by the allergic reaction. This enlargement can be seen with x-rays or ultrasound scanning. Prognosis and Treatment Kidney function usually improves when an offending drug is discontinued or treatment of the underlying disease is effective, although some kidney scarring is common. Treatment with a corticosteroid may speed the recovery of kidney function when the disorder is caused by an allergic reaction. If kidney function worsens and kidney failure develops, dialysis is usually needed. In some cases, the damage is irreversible, and kidney failure becomes chronic. When the inflammation occurs gradually, kidney damage may develop at different rates in different portions of the kidney. The person may develop abnormalities characteristic of damage to different portions of the kidney at different times. However, kidney damage usually progresses to involve most or all of the kidney and becomes irreversible. Irreversible kidney damage, whatever the cause, results in the need for dialysis or kidney transplantation. |
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