Effect of internal ureteral stenting of normal ureter on the upper urinary tract: an experimental study.

The effects of internal stenting of a normal ureter on the upper urinary tract were studied in 34 male rabbits by plain films, intravenous urograms, and 99mTc-DTPA renography at weekly intervals. Moreover, pressure-flow studies of the upper urinary tract were performed, and urine specimens for culture were obtained preoperatively and at the time of sacrifice. Histopathologic examination of the kidney, ureter, and ureterovesical junction was performed after animal sacrifice. Hydroureteronephrosis and stasis with equivocal obstruction were noted after 1 week of stenting. These changes were reversible after stent removal. Prolonged stenting (> 3 weeks) produced moderate to severe hydroureteronephrosis, and renal function was lost in 2 of 18 renal units because of severe hydronephrosis or infection. Ureteral stenting did not produce obstruction at a flow rate as high as 8 ml/minute. Histopathologic examination showed dilation of the pelvicaliceal system and renal tubules, infiltration of the kidney and the ureter with inflammatory cells, mucosal ulceration, and muscular hypertrophy of the ureters. The bladder mucosa showed a severe inflammatory reaction, Brunn nests, and ulceration with occasional metaplasia. Stenting of normal ureters in rabbits produced no harmful effects on the kidney if the stents were removed within 1 week, but prolonged stenting could affect renal and ureteral integrity.