The Morphology of Congenital Dilatation of the Ureter: Intrinsic Ureteral Lesions

Abstract

Congenitally dilated ureters are divided into four groups associated with (i) intrinsic ureteral lesions, (ii) vesico-ureteral reflux, (iii) urethral obstruction or (iv) other malformations such as myelomeningocele or the triad syndrome. One hundred and forty-seven dilated ureters in Group 1 (caused by Intrinsic ureteral lesions), have been studied qualitatively and quantitatively by standard pathological techniques, using the average size and population of muscle cells in the dilated ureter as the quantitative index of work-load or obstruction, and have been divided into four main types. These dilated ureters were found to be either obstructed or non-obstructed, and the obstructing lesion was either an atresia, a stenosis, or a valve. In each of the obstructed ureters, the smooth muscle in the wall of the proximal dilated ureter was hypertrophic and hyperplastic. In contrast, in the fourth non-obstructed type of dilated ureter, no obstructing lesion was found, and there was neither hypertrophy nor hyperplasia of muscle in the wall of the proximal dilated ureter; it is presumed that the dilatation is due to developmental lateral overgrowth of the ureter. No example of dilated ureter due to neuro-muscular incoordination was found in this group.