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Purpose: To investigate the effects of 1-arginine, a substrate for nitric oxide (NO) synthase, on renal hemodynamics in acute ureteral obstruction (UUO)., Materials and Methods: Renal blood flow (RBF) and ureteral pressure (UP) were measured in anesthetized dogs with or without UUO., Results: In 9 dogs (Group 1), RBF was 212 +/- 13 ml./min. before UUO, and significantly increased to 302 +/- 18 and 268 +/- 9 ml./min. at 90 and 140 min. post-UUO, respectively, associated with a marked increase in UP from 3 +/&#95; 1 mm. Hg to 73 +/- 5 and 83 +/-2 mm. Hg at 90 and 140 min. post-UUO, respectively. In 6 dogs (Group 2) prostaglandin synthesis was inhibited with meclofenamate (5 mg./kg., i.v.). After UUO, RBF did not change significantly and the increase in UP was markedly attenuated when compared with Group 1, as UP rose only to 27 +/-3 and 34 +/- 4 mm. Hg at 90 and 140 min. post-UUO, respectively. In 6 dogs pre-treated with meclofenamate, L-arginine was infused into the renal artery at 5 mg./kg./min. at 90 min. after UUO (Group 3). Prostaglandin synthesis inhibition prevented renal vasodilation after UUO and significantly attenuated the increase in UP. Upon infusion of L-arginine, RBF and UP rose sharply from 202 +/- 16 ml./min. and 24 +/- 6 mm. Hg to 264 +/- 22 ml./min. and 70 +/- 4 mm. Hg, respectively, at 140 min. post-UUO (p <0.001), values approaching those in Group 1. In sham-operated dogs, L-arginine infusion did not alter RBF in dogs with or without pretreatment with meclofenamate., Conclusion: In UUO the L-arginine-NO pathway is activated, contributing to renal vasodilation and a marked increase in UP.

We report on 3 pediatric patients with multicystic dysplasia involving 1 component of a horseshoe kidney. Including our cases, 18 cases of unilateral multicystic dysplasia in a horseshoe kidney have been reported. The clinical, radiological and pathological features of these cases are briefly reviewed. The association of multicystic dysplastic kidney and horseshoe kidney presents a unique diagnostic challenge. Because of the rarity of unilateral multicystic dysplasia in a horseshoe kidney and the size of the dysplastic component, which crossed the midline in our patients, we chose to excise that component. Cross-sectional imaging techniques, that is computerized tomography and magnetic resonance imaging, were helpful in diagnosis and in planning operative treatment.