Imperforate Hymen

Imperforate hymen is a congenital membrane completely occluding the vaginal introitus. It results from failure of the canalisation of the junction between the sinovaginal bulb and the urogenital sinus. Incidence is about 1 in 1,000 to 2,000 girls. It is usually sporadic, rarely familial.

Menstrual blood accumulates behind the membrane (haematocolpos), and later in the uterus (haematometra) and the fallopian tubes (haematosalpinx), producing retrograde menstruation and endometriosis. In neonates, maternal oestrogen may stimulate mucus secretion behind the membrane, producing a mucocolpos that bulges.

• Neonatal: bulging, grey white membrane at the introitus (mucocolpos), sometimes with an abdominal mass, urinary retention, hydronephrosis or respiratory distress.
• Adolescent (commonest): primary amenorrhoea with normal pubertal development, cyclic lower abdominal and back pain over months, a lower abdominal mass, urinary retention or frequency, constipation, dysuria, and pain on defecation.
• Examination: bluish bulging membrane at the introitus, especially with Valsalva; a lower abdominal mass (distended vagina and uterus); rectal examination palpates a tense bulging mass.
• Complications: acute urinary retention, hydronephrosis, endometriosis, pelvic adhesions, haematosalpinx, infection and pyocolpos, and later infertility.

• Clinical inspection of the genitalia in every girl with primary amenorrhoea and cyclic pain.
• Pelvic and perineal ultrasound: fluid filled distended vagina with low level echoes (haematocolpos), possibly with uterine distension; confirm normal uterus and ovaries and exclude renal anomalies.
• MRI if the picture is not clear, to distinguish imperforate hymen from transverse vaginal septum (where the bulge is higher in the vagina and the hymenal ring is visible) and from vaginal agenesis.
• Renal ultrasound for hydronephrosis.

• Definitive treatment is surgical hymenotomy (hymenectomy) under general or regional anaesthesia, or local anaesthesia with sedation in a cooperative adolescent, performed once the diagnosis is certain.
• Technique: a cruciate (X-shaped) or circular incision is made in the centre of the membrane; the dark, old blood is drained gently, without needle aspiration which risks infection, and the redundant membrane is excised, leaving a normal sized opening. The edges are oversewn with fine absorbable sutures (4-0 or 5-0 polyglactin) if bleeding or tendency to reclose. Avoid aggressive expression of blood from the uterus and tubes, and do not wash out the tubes (risk of peritonitis).
• Prophylactic antibiotics: a single dose of cefazolin 1 g intravenously if pyocolpos is suspected; give a full treatment course (co-amoxiclav 625 mg every 8 hours for 5 to 7 days) when infection is present.
• Neonatal mucocolpos: hymenotomy under local or general anaesthesia, or puncture and drainage; usually resolves with removal of membrane.
• After the procedure: the haematocolpos drains over days to weeks; follow up at 2 to 4 weeks and again at 3 months; with ultrasound to confirm resolution; advise on tampon and intercourse timing; instruct on gentle dilator use if the opening is narrow.
• Analgesia: paracetamol 15 mg/kg every 6 hours (adult 1 g) and ibuprofen 10 mg/kg every 8 hours (adult 400 mg).
• Long term outcome is excellent, with fertility preserved in most. Delay increases the risk of endometriosis, so early recognition is important; screen for endometriosis symptoms later.
• Familial cases and associated anomalies (polydactyly, renal anomalies, anorectal malformation) are checked.