Histologic study of the pyelo-ureteral junction

The ureter structure was analyzed under light microscope on serial sections in newborn children affected by obstruction of the pyelo-ureteric junction. In the obstructive segments, preceded by ureter portions dilated and provided with close-packed layers of smooth muscle layers, the tunica mucosa was lacking epithelial cover, its lamina propria was thickened, being built by conspicuous bundles of collagen fibers, and the tunica muscularis showed scarce and disrupted groups of muscle cells invaded by connective tissue. Numerous mastocytes were seen in the mucosa and muscularis tunicae. The results suggest that the breaking of the epithelium may be a primary pathogenetic event followed by passage of urine in the subjacent tissues in turn responsible for a diffuse connective reaction, and, therefore for a final fibrosis of the ureter wall. The role of the mastocytes in the etiopathogenesis of the pyelo-ureteric junction obstruction was also discussed.