COMPARISON OF RETROGRADE ENDO-PYELOTOMY AND ENDO-BALLOON RUPTURE OF THE URETEROPELVIC JUNCTION IN A PORCINE MODEL

Excellent results and durable success have been achieved with antegrad e and retrograde endo-pyelotomy for treating primary and secondary ure teropelvic junction obstruction. Recently, a 30F dilating balloon was used to rupture the ureteropelvic junction (ENDOBRST); with encouragin g results. While balloon distention of the ureteropelvic junction is a technically simpler procedure than endo-pyelotomy, clinical and labor atory data comparing the 2 methods are lacking. In an acute and chroni c animal study we compared endo-pyelotomy via a ureteral cutting ballo on incision to balloon rupture (that is 30F) of the normal ureteropelv ic junction in each of 20 female farm pigs. Eight pigs were harvested acutely after treatment, and a macroscopic and histological examinatio n of the treated ureteropelvic junction was completed. In 11 chronic p igs after endo-pyelotomy a 7F double pigtail ureteral stent was placed bilaterally and then removed after 6 weeks. Evaluation in the chronic group consisted of a furosemide washout renogram and retrograde pyelo gram immediately preoperatively and 6 weeks after stent removal. The a nimals were likewise harvested 6 weeks after stent removal. One contro l pig underwent passage of the balloon cutting catheter and balloon di lating catheters without activation or dilation, respectively. Uretera l stents were placed bilaterally for 6 weeks and the pig was otherwise treated similarly to the other chronic study animals. In the acute gr oup all ureters after endo-pyelotomy demonstrated retroperitoneal extr avasation of contrast material. At harvest the ureters had been cleanl y incised along a length of 3 to 4 cm. through the adventitial layer. In contrast, the balloon treated ureters showed free retroperitoneal e xtravasation in only half of the animals. Among the balloon treated ur eters 7 of 8 had a linear tear of varying length (1 to 5 cm.) involvin g all but a thin adventitial layer of tissue. Histologically, the endo -pyelotomy ureters demonstrated a clean, linear transmural incision wi th virtually no destruction of surrounding tissue in 6 cases. In the r emaining 2 cases an incision into but not completely through the muscu lar layer was observed. The balloon treated ureters showed a perforati on through the muscular wall in 7 cases. However, periureteral hemorrh age and urothelial loss were common findings. In the chronic group inf ection and continued urine extravasation from the endo-pyelotomy site resulted in a 45% mortality rate. Of the surviving 6 pigs 83% of the b alloon treated and 67% of the endo-pyelotomy pigs had a patent uretero pelvic junction by retrograde pyelogram and renogram. Histologically, the 2 sides were indistinguishable, with both showing mild fibrosis an d chronic inflammation. Overall, in the acute phase endo-pyelotomy pro vides a well defined, full thickness incision of the ureteropelvic jun ction. In contrast, balloon rupture of the ureteropelvic junction resu lts in a ureterotomy of unpredictable length, breadth and depth. Howev er, histologically, the 2 modalities are comparable in the chronic pha se. In this study balloon distention appeared to be safe and as effica cious as an endo-pyelotomy. The potential clinical relevance of these findings requires further study.