Functional effects of unilateral laser papillectomy in the pig

To evaluate the use of endoscopic laser papillectomy in a multi-papillary animal model to unilaterally impair concentrating ability and increase the urinary flow rate.

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, and the kidneys were examined histologically.

The urine flow rate per 100 mL creatinine clearance was significantly increased in the papillectomized kidney compared with the control kidney during hydropenia (1.50 versus 0.94, P <0.01). The papillectomized kidneys were unable to concentrate the urine as well as the control kidneys during both hydropenia (urine osmolarity 430 versus 534 mOsm/L, P <0.01) and after hydration (329 versus 362 mOsm/L, P = 0.02). The free water reabsorption per 100 mL creatinine clearance was impaired in the papillectomized kidneys compared with the control kidneys (0.48 versus 1.00, P = 0.02) after hydration. 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 transitional re-epithelialization with moderate collecting duct dilation and medullary fibrosis underlying the ablated papillae early in the series; however, the histologic features normalized and the creatinine clearance was less impaired with a more proficient technique later in the series.

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.