The effect of acute obstruction on ureteral function.

In an effort to understand the physiologic processes which contribute to, or hinder the transport of stones through the ureter, we examined the intraluminal ureteral pressures and peristaltic activity above and below the acutely obstructed site. Because of patient differences, variability in stone size, shape and composition, an in vivo animal model was developed to study acute ureteral obstruction. Five adult mongrel dogs were anesthetized. A midline celiotomy was made and an open-ended ureteral catheter was inserted through a distal ureterotomy and advanced up the ureter. An angiographic balloon catheter was inserted through a small nephrotomy and directed down the ureter. The experiment was divided into phases: control, ureteral obstruction (balloon inflation) and release of obstruction (balloon deflation). Compared to control values, peristaltic rate above the obstruction increased significantly (p less than 0.05), as well as baseline, peak, and delta (peak minus baseline) pressures. In contrast, the peristaltic rate below the obstructed site remained approximately the same as its control, despite the significant decreases in baseline, peak, and delta (p less than 0.05) pressures. Failure of transmission of effective peristalsis across the obstructed site may hinder stone passage; however, this remains to be proven. Moreover, the failure of transmission of the increased rate of peristalsis past the balloon and persistence of peristaltic activity below the site of obstruction despite absence of urine flow suggest segmental forces influence peristaltic activity.