Ureteral compliance and histology in partial obstruction in a canine model

Standardized partial ureter obstruction was achieved in 35 mongrel dogs in whom ureteral compliance and its relationship to histologic changes were studied over a period of 26 weeks. The partially obstructed ureter became dilated with thickened wall and showed muscle hypertrophy and connective tissue proliferation. The normal stellate configuration of the ureteral lumen gradually flattened and became entirely circular by the eighth week. The compliance of the obstructed ureter increased gradually after one, 2, 4, and 8 weeks but decreased thereafter at 12 and 26 weeks. At 8 weeks, the ureter was significantly more compliant than both, the unobstructed control ureter (p less than 0.005) and the 12 week and 26 week partially obstructed ureters (p less than 0.005 & p less than 0.05 respectively). The increase in ureteral compliance was proportional to the amount of muscle hypertrophy during the first 8 weeks while the subsequent decrease in compliance (at 12 and 26 weeks) was proportional to the amount of connective tissue proliferation. This study documents ureteral response, both functional and histologic, to partial obstruction in a canine model over 26 week duration.