Glomerulonephritis. Light micrograph of three glomeruli (dark blue) in a human kidney affected by glomerulonephritis. In this condition there is a proliferation of enlarged epithelial cells that line the glomerular capillaries, and the presence of increased numbers of neutrophils (red/purple, blood cells). The glomeruli thus take on a dense appearance, as seen here. Glomerulonephritis is the most common cause of kidney failure, occurring often after a bacterial infection. The inflamed & obstructed glomeruli cause red blood cells and proteins to leak into the urine, and the patient retains fluid. Magnification: x50 at 35mm size.