The vesico-ureteric junction in three cases of primary obstructive megaureter associated with ectopic ureteric insertion.

OBJECTIVE To examine the histological structure and autonomic innervation of the vesico-ureteric junction (VUJ) in three cases of primary obstructive megaureter occurring in association with ectopic ureteric insertion. PATIENTS AND METHODS Specimens of VUJ were obtained from one male and two females with primary obstructive megaureter and ectopic ureteric insertions. Serial frozen sections were cut and stained with either Masson's trichrome or immunostained for protein gene product (PGP 9.5; a general nerve marker) or dopamine beta-hydroxylase (DbetaH), a marker for noradrenergic nerves. RESULTS In each case examined the terminal ureter was encircled by a thick collar of smooth muscle on the inside of which lay normal narrow-diameter longitudinally orientated ureteric muscle bundles. Loose connective tissue separated the surrounding detrusor muscle from this abnormal muscle collar, which was formed of distinctive smooth muscle cells arranged in a meshwork. The autonomic innervation of the ureteric and detrusor muscle bundles was similar to that previously reported for the normal VUJ while the thick muscle collar was richly innervated by DbetaH-immunoreactive noradrenergic nerves. CONCLUSION The presence of an additional smooth muscle collar surrounding the terminal ureter may impede the normal flow of urine from ureter to bladder and be the cause of megaureter in these patients. We propose that the presence of this muscular collar arises from the developmental anomaly and suggest that these cases represent a subgroup that requires early surgical treatment.