A 13-year-old girl is brought to the office due to lower abdominal pain for the past 4 days. The patient has rectal pain with bowel movements, but no melena or frank blood. She has had this pain several times over the past year, but it usually resolves after 2 or 3 days. She has no fever, chills, nausea, vomiting, loss of appetite, dysuria, hematuria, or abnormal vaginal discharge. The patient has no chronic medical conditions or previous surgeries. She has not reached menarche and has never been sexually active. Temperature is 36.7 C (98 F) and blood pressure is 110/70 mm Hg. BMI is 24 kg/m². Physical examination shows a nondistended abdomen without rebound or guarding. There is lower abdominal tenderness to deep palpation in the midline. The external genitalia are Tanner stage 3. On pelvic examination, a smooth, firm mass is protruding between the labia majora. Which of the following is the most likely diagnosis?

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11ec25c8_d60f_81b3_bc81_47f049b809f8_MD0003_00 An imperforate hymen is a common anatomic cause of primary amenorrhea. This occurs when the hymen fails to fenestrate during embryonic development. Infants may present with a bulging membrane due to mucus collection, but this typically resolves and patients remain asymptomatic until menarche. Adolescent patients with an imperforate hymen typically present with cyclic lower abdominal pain in the absence of apparent vaginal bleeding. When menstruation occurs, blood collects in the vagina behind the hymenal membrane (eg, hematocolpos). The enlarging blood collection with each menstrual period causes increasing pressure on the surrounding pelvic organs, resulting in lower back pain, pelvic pressure, or defecatory rectal pain. Pelvic examination typically reveals a blue, bulging vaginal mass or membrane that swells with increased intraabdominal pressure (eg, Valsalva). External genitalia and pubic hair development is normal. Treatment is with incision of the hymen and drainage of the hematocolpos. Patients with abnormal genital tract development should be evaluated for associated renal abnormalities with renal ultrasound. (Choice A) A uterine leiomyoma may present with bulk symptoms (eg, rectal pain or pressure), and a cervical leiomyoma presents as a protruding cervical rather than a vaginal mass. Leiomyomata are associated with heavy vaginal bleeding rather than amenorrhea. (Choice B) Choriocarcinoma typically presents with vaginal bleeding, markedly elevated β-hCG levels, and an enlarged uterus. The vagina is a common site of metastasis, presenting as a friable mass. (Choice C) Complete müllerian agenesis may present with amenorrhea and a blind vaginal pouch due to the congenital absence of the uterus and cervix. Because the uterus is absent, patients do not have cyclic abdominal pain or associated hematocolpos. (Choice D) A foreign body in the vagina typically presents with abdominal pain, foul-smelling vaginal discharge, and vaginal bleeding, and is seen on examination. (Choice F) Pelvic organ prolapse may present with pelvic pressure and a vaginal bulge that increases with Valsalva. Pelvic organ prolapse is more typical in postmenopausal patients and is not associated with primary amenorrhea. (Choice G) Sarcoma botryoides, a form of rhabdomyosarcoma, typically presents during infancy as a polypoid or "grapelike" mass protruding from the vagina with associated vaginal discharge and bleeding. Educational objective: Imperforate hymen is an anatomic cause of primary amenorrhea. Pubertal patients typically present with cyclic lower abdominal pain, amenorrhea, and hematocolpos. Pelvic examination typically reveals a smooth, blue, bulging vaginal mass that swells with increased intraabdominal pressure. References: Imperforate hymen: a cause of abdominal pain in female adolescents. (http://www.ncbi.nlm.nih.gov/pubmed/21686660)

A 13-Year-Old Girl Is Brought to the Office Due to Lower