The incidence and significance of vaginal metaplasia of the bladder trigone in adult women.

One hundred and six bladders were removed at autopsy from adult women dying of diseases unrelated to the urinary tract. A fixative solution had been introduced into the bladder as soon as possible after death. The naked-eye appearances were recorded before and after application of Lugol's iodine solution and the trigones then submitted to histological examination. Vaginal metaplasia of the trigone was present in the majority (72%) of bladders, a similar incidence being found in both pre-menopausal and post-menopausal age groups. Histological evidence of chronic inflammation was found significantly more frequently in bladders showing vaginal metaplasia and it is suggested that vaginal metaplasia is not a consequence of chronic inflammation but that its surface characteristics may predispose to chronic infection. Its purported hormonal aetiology does not explain all observed features. Prominent venous channels within the tunica propria around the urethral orifice were a constant feature in all bladders studied. Two of the 76 bladders showing vaginal metaplasia also displayed atypical hyperplasia of this squamous epithelium, a previously unrecorded observation. The possible implications of such atypical hyperplasia are briefly discussed.