Impaired renal concentrating capacity in the rat after surgical resection of the papilla.

Renal cortical and medullary function was examined in rats 4 weeks after surgical resection of the distal portion of the renal papilla had been performed. Glomerular filtration rate (GFR), obtained during the determination of free water reabsorption (TcH2O) at high rates of urine flow, did not differ significantly among controls (1.62 +/- 0.19 ml/min, n = 5), sham operated animals (1.45 +/- 0.16, n = 4) and papillectomized animals (1.49 +/- 0.21, n = 7). Maximum urinary osmolality (Umax) was 2216 +/- 293 mOsm/kg in controls, and was significantly reduced in sham operated (1737 +/- 261, P less than 0.05) and papillectomized animals (889 +/- 143, P less than 0.0001). TcH2O was normal in sham operated animals at high rates of osmolar clearance (Cosm), but was significantly impaired after resection of the renal papilla. These results suggest that removal of the terminal collecting ducts and interruption of nephrons with long loops extending into the papilla impair the maximal generation of solute free water.