[Three cases of hydronephrosis in which the indwelt ureteral stent was ineffective. Urodynamic studies using a stent indwelling model for retroperitoneal fibrosis].

We report 3 cases in which ureteral stents were indwelt to treat hydronephrosis due to retroperitoneal fibrosis, resulting in aggravation of hydronephrosis and renal function. An urodynamic study was carried out to determine the factors that aggravated hydronephrosis. The subjects were a 59-year-old male with prostatic cancer and bilateral hydronephrosis due to intrapelvic lymph node metastasis, a 49-year-old female with retroperitoneal lymph node metastasis and bilateral hydronephrosis following surgery for stomach cancer, and a 65-year-old male with hydronephrosis due to idiopathic retroperitoneal fibrosis. Indwelling of ureteral stents in the 3 patients resulted in aggravation of hydronephrosis and renal function. Stent indwelling models of retroperitoneal fibrosis were produced using adult mongrel dogs. A pressure flow study was carried out through the nephrostomy in each experimental model to determine the intrapelvic pressure and urine volume. In all stent indwelling models, the urine volume showed changes similar to those in the controls. In the stent indwelling models, the intrapelvic pressure showed a significant increase with an increase in the volume of water instilled through the nephrostomy in the stent indwelling models with retroperitoneal fibrosis, unlike the controls and models with ureteral stenosis. In conclusion, the clinical cases and model experiment suggested that unlike partial ureteral stenosis, in ureters in which extensibility was disturbed in an extensive area, the indwelt stent caused an increase in the resistance of the liquid flowing in the ureter, aggravating hydronephrosis.