Different phenotypes of dysplastic kidney in obstructive uropathy in fetallambs

Purpose: The cause of cyst production in renal dysplasia is uncertain. The authors hypothesized that different patterns of renal dysplasia result from variations in the timing and site of the urinary tract obstruction. Methods: The authors operated on fetal lambs at 50 and 60 days' gestation. Male lambs underwent urethral and urachal ligation and female lambs unilate ral ureteric ligation. They were delivered by cesarean section at 145 days' gestation and killed. Results: Of 12 lambs operated on at 50 days' gestation, 4 survived. Of 26 l ambs operated on at 60 days, 21 survived, The authors identified 3 types of dysplastic kidneys. Type A, fibrotic kidneys (2.2 g) with no cysts and int erstitial fibrosis. There were reduced numbers of proximal tubules, but dis tal tubules and collecting ducts persisted. (50-day obstruction, n = 5 kidn eys); type B, Sponge-like kidneys (37g): these had large cysts with minimal interstitial fibrosis. (87% of 60-day uretheral and urachal ligation model n = 12 kidneys); Type C, Small kidneys (4.8 g) with no large cysts (60-day Ureteric ligation model n = 7 kidneys). Conclusion: The authors produced 3 different types of renal dysplasia by cr eating urinary tract obstruction at different sites and gestational ages. J Pediatr Surg 36:1698-1703. Copyright (C) 2001 by W.B. Saunders Company.