Morphometric analysis of smooth muscle in the exstrophy-epispadias complex

In bladder exstrophy and to a lesser extent in epispadias the muscular tissue in the bladder wall may often be replaced by collagen. The aim of our study was to assess the relative changes of smooth muscle versus connective tissue in patients with the exstrophy-epispadias complex.

Nine full thickness detrusor biopsies from children with the exstrophy-epispadias complex were analyzed. Biopsies were stained with the Masson trichrome method to differentiate muscular tissue from collagen. At x50 magnification using image software for computerized morphometry the areas of smooth muscle and collagen were measured and expressed as a percent. As controls, detrusor biopsies from 8 children with unilateral obstructive megaureter or ectopic ureter were analyzed using the same method.

The average rates of smooth muscle in children with the exstrophy-epispadias complex were 7, 19.3 and 31.5%, respectively, in newborns, and before and after bladder neck reconstruction. In controls the rate averaged 56.5%.

The ratio of smooth muscle-to-connective tissue increases from the newborn period to puberty in the exstrophy-epispadias complex. After staged reconstruction is completed this ratio remains below normal, although it is increased. Such a change may represent a histological marker of the inadequate volume increase of some of these bladders.