Histological findings in pseudomembranous trigonitis.

Pseudomembranous trigonitis presents in females with the urethral syndrome and a characteristic lesion restricted to the trigone of the bladder. The histology shows ;vaginal metaplasia' of the epithelium together with underlying oedema and vascular dilatation, but no significant inflammation. Thirty-one such cases are included in the study. The possible role of oestrogen stimulation is discussed, together with a suggestion that the trigone has an embryological derivation distinct from the remainder of the bladder, allowing the trigonal epithelium to respond to oestrogenic stimulation in a manner denied to the vesical transitional epithelium.