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INTRODUCTION ? Glomerular disease, or glomerulonephritis, is an inflammation of the glomeruli of the kidney. Glomeruli are structures composed of blood vessels, and are the first part of the kidney's filtering process. These structures are surrounded by tubules and tissues called the tubulointerstitial tissue.

In glomerulonephritis, inflammation of some or all of the glomeruli reduces their ability to filter a number of substances out of the bloodstream. The result is that blood, protein, and lipids (fat structures) tend to be excreted into the urine. Eventually, damage to the glomeruli leads to increasing impairment, and as less urine is produced, more metabolic waste is left to build up in the blood. This may lead to renal failure.

PATTERNS OF GLOMERULONEPHRITIS ? Although there are specific clinical patterns characteristic of glomerular disease, many of these clinical findings are also common to other kidney diseases. The first suggestion that the glomeruli are involved is often the presence of blood in the urine (called hematuria), particularly malformed red cells and those with casts, or tiny deposits of minerals, attached to them. Proteins and lipids in the urine are also suggestive of glomerular inflammation, as these do not usually cross the glomerular membranes from the blood.

Although a biopsy of the kidney is generally used for definitive diagnosis of glomerular disease, there are certain factors and patterns of clinical findings that can help physicians narrow down the possibilities. One factor is the patient's age, while the other is the characteristics of the urine sediment, which can be broken down into three general histologic (microscopic appearance) patterns: focal nephritic, diffuse nephritic, and nephrotic.

Each of the following three patterns can be caused by a wide variety of primary kidney diseases, as well as some diseases that affect the kidney as well as other organs (systemic diseases).

Focal glomerulonephritis ? In this type of glomerular disease, less than one-half of the glomeruli show inflammatory lesions. Urinalysis (which is evaluation of the urine) usually shows the presence of red blood cells, many of which are malformed, occasional red cell casts (cells encased in a small waxy structure), and a mild level of protein. Patients with this type of glomerulonephritis do not usually show symptoms of more severe kidney disease, such as high levels of protein in the urine, edema (water retention that causes swelling in the extremities), high blood pressure, or kidney dysfunction. In fact, they may not have any symptoms and their condition may go unnoticed until blood and protein in the urine are found during routine examinations.

Diffuse glomerulonephritis ? This type of glomerular disease affects most of the glomeruli. Urinalysis usually shows high levels of protein, and symptoms and signs such as edema, hypertension, and kidney dysfucntion may be observed.

Nephrotic syndrome ? This form of glomerular disease is characterized by large amounts of protein and fats (or lipids) in the urine, but few red blood cells or casts. It is harder to differentiate nephrotic syndrome from other kidney diseases, because the symptoms and clinical findings can also be caused by a number of other conditions, including diabetes mellitus.

CAUSES AND TREATMENT ? These patterns can be caused by a wide variety of primary kidney diseases, as well as some diseases that affect the kidney as well as other organs (systemic diseases). Thus, a discussion of the causes and treatment of these patterns is beyond the scope of this review.

WHERE TO GET MORE INFORMATION ? Your doctor is the best resource for finding out important information related to your particular case. Not all patients with glomerular disease are alike, and it is important that your situation is evaluated by someone who knows you as a whole person.

A number of other sites on the Internet have information about glomerular diseases. Information provided by the National Institutes of Health, national medical societies, and some other well-established organizations are often reliable sources of information, although the frequency with which their information is updated is variable. Go to links page >>