Functional effects of unilateral laser papillectomy in the pig

Objectives. To evaluate the use of endoscopic laser papillectomy in a multi -papillary animal model to unilaterally impair concentrating ability and in crease the urinary flow rate. Methods. Domestic pigs underwent unilateral retrograde flexible nephroscopy . With a holmium:yttrium-aluminum-garnet laser, varying numbers of papillae were ablated. Four weeks after the procedure, renal function studies were performed during hydropenia and after hydration, the animals were killed, a nd the kidneys were examined histologically. Results. The urine flow rate per 100 mt creatinine clearance was significan tly increased in the papillectomized kidney compared with the control kidne y during hydropenia (1.50 versus 0.94, P <0.01). The papillectomized kidney s were unable to concentrate the urine as well as the control kidneys durin g both hydropenia (urine osmolarity 430 versus 554 mOsm/L, P <0.01) and aft er hydration (329 versus 362 mOsm/L, P = 0.02). The free water reabsorption per 100 mt creatinine clearance was impaired in the papillectomized kidney s compared with the control kidneys (0.48 versus 1.00, P = 0.02) after hydr ation. A significant correlation existed between the percentage of papillae ablated and the difference in osmolarity between the operated and control kidneys (r(2) = 0.50, P = 0.015). Histologic examination demonstrated trans itional re-epithelialization with moderate collecting duct dilation and med ullary fibrosis underlying the ablated papillae early in the series; howeve r, the histologic features normalized and the creatinine clearance was less impaired with a more proficient technique later in the series. Conclusions. Endoscopic laser papillectomy results in increased urine flow and impaired urinary concentrating ability. This surgical technique should be investigated further for its role in the prevention of nephrolithiasis. UROLOGY 57: 832-836, 2001. (C) 2001, Elsevier Science Inc.