INTRODUCTION

Hematocolpos or the accumulation of menstrual blood in the vaginal cavity is due to some lower genital tract malformations, the commonest being imperforated hymen and complete transverse vaginal septum.1-4 These malformations sometimes go unnoticed until puberty when they are responsible for primary amenorrhoea, cyclic pelvic pain, difficult sexual intercourse and acute urinary retention.3 Long term complications like endometriosis and infertility are possible. We report on a case of hematocolpos discovered after the patient had presented an acute urinary retention. The hematocolpos was secondary to a thin retro-hymeneal transverse vaginal septum that might have been mistaken for an imperforated hymen if careful clinical and histologic examinations were not done.

Case report

A 17 year-old married woman, Gravida 0, consulted on the 7th November 2011 for acute urinary retention that appeared 2 days ago associated with pelvic pain. Acute urinary retention was preceded by frequent micturition and pelvic heaviness. She had never menstruated and never succeeded in having sexual intercourse. For about two years, she presented cyclic pelvic pain that lasted 3 days each time.
On physical examination, conjunctivae were coloured, secondary sexual characters were present. There was a suprapubic renitent mass of 18 cm largest diameter. Hymen was perforated but distended with a membrane occluding the perforated hymen (fig.).

Figure 1

Retro-hymeneal transverse vaginal septum

The diagnosis of acute urinary retention due to a huge hematocolpos was done. Urine was evacuated with an indwelling catheter. A combined rectal and abdominal examination revealed a around 12 cm pelvic mass. Under general anesthesia, a cruciate incision on the hymen and that membrane was done and 1100 ml dark blood was collected. After careful examination, the juxta-hymeneal membrane was found to be a thin complete transverse vaginal septum. This was later confirmed by histology. Three months later an intravenous pyelogram and an abdominal ultrasound scan revealed no other malformations, but on vaginal examination another (incomplete) transverse septum was discovered in the upper third of the vagina. This was completely excised.

Discussion

Absence of menses in a girl who has secondary sexual characters and cyclic pelvic pain is almost synonymous with hematocolpos. Hematocolpos is retention of menstrual blood in the vaginal cavity. It is a rare affection, its incidence being between 0.5 and 1/1000 female.1 Aetiologies include imperforated hymen, transverse vaginal septum, coalescence of labia minora, and partial vaginal agenesis. Imperforated hymen seems to be the commonest cause.1-4 Another cause is transverse vaginal septum.5 In our case the cause was initially thought to be an imperforated hymen, but after careful examination we discovered a hole on the hymen behind which laid a vaginal septum. This was confirmed histologically.
Thin lower situated transverse vaginal septum might be mistaken for an imperforated hymen. Therefore, histological examination of the tissue is important for confirmation. This is very important because imperforated hymen is rarely associated with other genito-urinary tract malformations while this is possible with vaginal septum.2 Further extensive investigations might be needed in vaginal septum, but not in imperforated hymen.2 In our case after exploration, an incomplete transverse vaginal septum situated in the upper third of the vagina was discovered.
Causes of hematocolpos should be treated rapidly to avoid long term complications like endometriosis and infertility.

Conclusion

This case report reminds us that a thin retro-hymeneal vaginal septum might mimic imperforated hymen. It is important to differentiate between the two pathologies because further extensive investigations might be necessary in vaginal septum but not in imperforated hymen given that a vaginal septum might hide another one.