A Rare Pelvic "Mass-Querader": Acute Urinary Retention Secondary to Hematocolpos in a Preadolescent Patient.

We report a case of acute urinary retention in an adolescent female secondary to hematocolpos. A 13-year-old female presented to the emergency department with acute urinary retention and suprapubic abdominal pain for 24 hours. She denied menstruation or sexual history. Bedside bladder ultrasound scan revealed 1.2 L of retained urine and a Foley catheter was placed. A formal renal ultrasound detected a debris-filled structure in the abdomino-pelvic cavity. Follow-up computed tomography of the abdomen and pelvis revealed an 8.5 cm × 9.3 cm × 12.1 cm mass-like structure in the pelvis. No formal pelvic exam was completed and the patient was taken to the operating room for exploratory laparotomy due to concern for large pelvic mass versus tubo-ovarian abscess. However, upon entering the abdominal cavity, no mass was found. At that point, an external genital exam was performed, revealing an imperforate hymen. Hymenotomy resulted in the evacuation of 2.5 L of clotted blood from the vagina and uterus. Hematocolpos resulting in acute urinary retention is exceedingly rare; however, it is an important differential diagnosis that can be ruled in or out by physical exam findings. Although it may be uncomfortable for adolescent patients and physicians, external genital exams should be conducted in young females with acute urinary retention and amenorrhea to evaluate for imperforate hymen. This can ensure appropriate treatment and avoidance of unnecessary invasive procedures.