Pathology of ureterorenal units in various ureteral anomalies with particular reference to the genesis of renal dysplasia.

Renal morphology of various congenital ureteral anomalies was investigated to gain further insight into the genesis of associated renal dysplasia. Abnormality in the ureteral bud explains the genesis of renal dysplasia as long as the adjoining ureter is cranially ectopic. In caudal ectopy of either single or duplex system, no difference was found in the histologic quality of kidneys with G and H position orifice. In the single system kidneys of H position orifice, however, occurrence of renal dysplasia was not associated with obstruction, suggesting the operation of the "bud theory" even in single system caudal ectopy. In anomalies in which the ureteral orifice was not ectopic, it was suggested that renal parenchymal development was impaired by complete, but not by incomplete obstruction. The association of dysplastic ureter and renal dysplasia was not so frequent as anticipated and the hypodysplastic values of the kidneys with and without dysplastic ureters were similar, suggesting no direct causal relationship between them.