Acute Glomerulonephritis

The term acute glomerulonephritis is used by clinicians as well as pathologists to describe the sudden onset of kidney disease. Irrespective of the cause, there would be enlargement of a kidney or kidneys and the capsule around the kidney is strained and stretched. Ultrasonography is always helpful to ascertain the size of kidneys. Histological examination of kidney biopsy would present densely cellular glomerular tuft with polymorphonuclear cells (a type of white blood cells) in the glomerular capillaries. Accumulation of leukocytes (white blood cells) in the glomerular capillaries with swelling and proliferation of the vascular endothelium (inner lining of capillaries) is rapidly followed by edema (swelling) and mesangial proliferation (enlargement of inner stalk of a cluster of glomerular capillaries)leading to capillary ischemia (poor blood supply).

The glomerular basement membrane (GBM) is the other important component affected by acute glomerulonephritis. By electron microscopic study of kidney biopsy, electron dense deposits of antigen-antibody complexes could be revealed in and around the glomerular basement membrane. The ultrastructural features of normal GBM have been depicted in the figure-1 and the figure-2 is from a case affected by acute glomerulonephritis.

Figure-1: Electron micrograph of a capillary loop of glomerular tuft showing normal features; CL: capillary lumen, US; urinary space, En: endothelium, GBM: glomerular basement membrane, EpC: epithelial cell or podocyte.

Figure-2: Electron micrograph of a capillary loop of glomerular tuft from a case affected by acute glomerulonephritis is showing sub-epithelial deposits; CL: capillary lumen, US; urinary space, GBM: glomerular basement membrane, dep: deposits on sub-epithelial site of GBM.

The tubules in the kidney may show slight degenerative changes. The degree of degenerative changes in the tubules depends on the extent of the glomerular obstruction. The interstitial tissue and the blood vessels are observed to be normal on the histological study of kidney biopsy.