Unilateral obstructive nephropathy in the rabbit. II. Late morphologic changes.

The late histologic and ultrastructural effects of complete unilateral ureteral obstruction in the rabbit kidney were studied from 7 to 32 days postobstruction. Papillary necrosis occurred in all animals by the 7th day. There was progressive widening of the cortical interstitial space with proliferation of fibroblasts. Increased interstitial collagen fibers first became apparent on the 7th day and showed a progressive increase with time. The fibroblasts underwent myofibroblast transformation beginning on the 7th day. All segments of the nephron showed ultrastructural evidence of sublethal cell injury with loss of cell specialization. The dedifferentiation of the tubular cells was associated with a repetitive formation of new lamellae of basement membrane on the luminal side of the original basement membranes beginning on the 16th day of obstruction. These morphologic changes are discussed in terms of the physiologic changes previously reported in this model and the known clinical abnormalities found in obstructive uropathy.