Smooth muscle regeneration in swine ureters: a light and electron microscopic study.

Intubated ureterotomies were performed on 16 juvenile pigs. The animals were killed at intervals of from 2 to 91 days after operation and tissue sections examined with light and electron microscopes. Ureteral wall replacement occurred within the 3 months after operation and included all tissue layers. Epithelialization of the wound surfaces occurred in the 1st week and was accompanied by a connective proliferation. Smooth muscle bridged the defect within 5 weeks and the margins of the muscularis were thickened and cellular in early stages; cells were elongated and extended towards the defect from the muscular remnant. Primitive smooth muscle cells were present at defect margins. This evidence indicates that smooth muscle was replaced by hyperplasia.