Renal ultrastructure in lamb nephrosis

Ultrastructural investigation of the kidneys of 18 lambs with clinical nephrosis revealed that groups of tubules showing various degrees of degeneration up to necrosis could exist alongside tubules showing proliferative or regenerative changes. Lesions were most common in proximal convoluted tubules, less common in distal tubules and absent from collecting ducts or straight tubules, though the latter were often distended with hyaline or flocculent casts. The basement membranes of necrotic tubules were intact, suggesting that the potential for regeneration was unimpaired. Nine lambs had lesions in the glomeruli, though the distribution was focal. Glomerular lesions occasionally were acute and degenerative but more usually were proliferative, with occlusion of capillaries due to endothelial swelling and mesangial encroachment. Basement membrane splitting or reduplication was a feature of some glomeruli, but neither subepithelial nor subendothelial dense deposits were seen. The changes were consistent with damage by an unknown nephrotoxic factor or factors.