New experimental model of ureteropelvic junction obstruction allowing easy access for percutaneous surgery

To assess the usefulness of an experimental model of ureteropelvic junction (UPJ) obstruction designed to facilitate subsequent percutaneous surgery, a right UPJ obstruction was created in 10 pigs by an open retroperitoneal surgical approach. With the pig in the left lateral decubitus position, a 0.038-inch Terumo guidewire was inserted via a 1-cm longitudinal upper-third ureterotomy and advanced up and down so as to bridge the UPJ from the flank to the urogenital opening. A UPJ obstruction was then induced by securing two 2-0 chromic gut ties, separated by an interval of 1 cm, over the Terumo guidewire and a 6F ureteral catheter, which was removed immediately after this procedure. After closure of the ureterotomy, the kidney was anchored horizontally to the muscle wall, and the Terumo guidewire was coiled subcutaneously in the flank and fixed to the urogenital opening. Each pig developed marked hydronephrosis, diagnosed by ultrasonography, after a mean interval of 8.3 days. Retrograde ureteropyelography confirmed this pronounced dilation of the right collecting system above a tight UPJ stricture (mean length 1.17 cm). Subsequent percutaneous access to the UPJ over the Terumo guidewire in the lateral decubitus position was facilitated by the almost-horizontal plane of dilation (mean operating time 14 minutes). Pathologic examination of the UPJ revealed mild periureteral fibrosis, but the muscle layer and urothelium remained normal. We have developed a reliable and reproducible model of secondary UPJ obstruction especially designed for percutaneous surgery. This model should provide a better understanding of current endoscopic techniques such as endopyelotomy and could help to promote new treatment concepts such as percutaneous endoscopic pyeloplasty.