Glomerulonephritis. Light micrograph of tissue from a kidney in a case of glomerulonephritis. This condition refers to inflammation of the glomeruli, the filtering structures of a kidney. The glomerulus is the round structure seen here. In the chronic form, the renal glomeruli and tubes atrophy, turn fibrous, and fail. This micrograph shows mesangiocapillary glomerulonephritis. Here all segments of the glomerulus have undergone mesangial endothelial cell proliferation and marked widespread basement membrane thickening.