The structure of the pelvis in the immature human kidney.

Examination of the renal pelvis of late fetal and neonatal kidneys shows that in about one quarter of the calyces examined the arrangement is similat to that in the rat, the outer medulla being separated from the calyceal cavity by a very thin epithelium. It is suggested that this presents a vulnerable area through which intrarenal damage can occur as a result of vesico-ureteric reflux in the immature kidney.