Glomerulonephritis, an immunologic disease of the kidneys, affects the glomerulus. This structure, a cluster of capillaries, is the filter in the functioning unit of the kidney, the nephron. Inflammation, initiated by immune complexes (defined below), injures the glomerulus. Often the disease is acute, but it may be silent and completely undetected until signs and symptoms of chronic kidney failure prompt a biopsy, leading to diagnosis. Alternatively, this silent disease may prove fatal, and the diagnosis is made at autopsy.

The urine-secreting structure (nephron) (Figure VIII.60.1) consists of the glomerulus and its tubular system. Each glomerulus consists of a tangle of interconnecting capillaries branching between two tiny arteries (arterioles). A glomerular cross section shows these capillary loops (Figure VIII.60.2). The glomerulus is a blood filter that controls passage of molecules through the basement membrane, depending on their size and charge. Normally red blood cells and albumin are not permitted to pass through the membrane. The tubules reabsorb, secrete, synthesize, and excrete solutes and metabolites, thereby maintaining physiological equilibrium.

This article will deal only with poststreptococcal glomerulonephritis. This disease, described by Richard Bright in the early part of the nineteenth century, still bears his name. Other forms of glomerulonephritis, which he also described, and the glomerular diseases termed glomerulopathies, seen in diabetes or amyloidosis, are not discussed.

Distribution and Incidence

Glomerulonephritis occurs worldwide. The disease was seen frequently in Europe during the eighteenth and nineteenth centuries as a complication of scarlet fever during epidemics. Today glomerulonephritis occurs sporadically. Several epidemics have occurred since the 1950s in the United States, Trinidad, and Venezuela.