The changes in acute nephritis are characterized by diffuse intracapillary proliferative glomerulonephritis, and the main structures in the kidney are the glomeruli, renal tubules, and renal interstitium. Therefore, pathological examination can be divided into light microscopy, immunofluorescence, and electron microscopy examinations.

Under light microscopy, the pathological changes in acute nephritis mainly include proliferation of mesangial and endothelial cells in the glomeruli. In the acute phase, there is significant infiltration of neutrophils and mononuclear cells. Masson's trichrome staining can reveal subepithelial immune complex deposits, and there is also edema and infiltration of inflammatory cells in the interstitium;

Immunofluorescence examination shows diffuse coarse granular deposits of immune complexes along the capillary walls and in the mesangial areas, mainly composed of IgG and C3;

Under electron microscopy examination, there are hump-like electron-dense deposits beneath the epithelial cells.