Three-D muscular arrangement at the ureteropelvic junction and its changes in congenital hydronephrosis: a stereo-morphometric study.

Ureteral walls were obtained from twelve autopsies without urological diseases and from surgical material of twelve patients operated for congenital hydronephrosis. The specimens were submitted to computer-assisted analysis of 3-D muscular architecture at the ureteropelvic junction (UPJ). Serial histologic sections in parallel with the wall were prepared. A geometric model was introduced to simplify the muscular layer, replacing bundles with vectors of corresponding size and direction. The vector distribution visualized that normally, the ureteral muscles change their arrangement with age, from a circular pattern in neonates to an oblique mesh in adults. In addition, longitudinal muscles emerged at the age of two years in the subepithelial layer. In patients with congenital hydronephrosis, not only were such growth-related changes ambiguous or lacking, but there also were various abnormalities; segmental muscular hypoplasia, disarrangement of bundles or lack of longitudinal fibers. These were considered to closely correlate with the urinary obstruction in patients with this disease.