Prenatal diagnosis of isolated fetal hydrocolpos secondary to congenital imperforate hymen.

A 32-year-old primigravida was referred to our hospital at 36 weeks of gestation with a fetal pelvic mass. Ultrasonography showed the fluid-filled area to be a 9 x 4 x 5-cm pear-shaped retrovesical mass with a funnel-shaped blind pouch at the distal end of the fetal vagina. Marked left hydronephrosis resulting from mass compression was also detected. Fetal magnetic resonance imaging further defined a pelvic lesion extending cephalically into the abdomen and caudally into the vagina. Membranal protrusion of the introitus was clearly identified. Therefore, the diagnosis of congenital imperforate hymen with hydrocolpos was established. At 38 weeks of gestation, a 2,966-g female infant was delivered vaginally with good Apgar scores. Physical examination of the neonate revealed a bulging membrane covering the vaginal opening. The presence of syndromic disorders (McKusick-Kaufman, Ellis-van Creveld or Bardet-Biedl syndromes), genitourinary and anorectal anomalies were excluded. The karyotype was 46,XX. A hymenotomy was performed on the second day of life. The infant recovered fully after hymenotomy.