Isolated Fallopian Tube Torsion in a 16-Year-Old Adolescent: A Diagnostic Challenge Mimicking a Functional Ovarian Cyst.

Isolated fallopian tube torsion (IFTT) is a rare cause of acute abdominal pain in adolescents. Its preoperative diagnosis is often challenging because imaging findings are usually nonspecific. Here we report the case of a 16-year-old girl with IFTT that closely mimicked a functional ovarian cyst. The patient, who had no history of abdominal surgery or pelvic infection, presented with persistent left lower quadrant pain. Initial computed tomography and ultrasonography showed a 30-mm simple cyst without signs of a twisted vascular pedicle, and a functional ovarian cyst was suspected. Her pain persisted, and on day 5 repeat ultrasonography again demonstrated the same simple cyst as at the initial visit, but the left ovary was clearly visualized separately, raising suspicion of a tubal origin. Diagnostic laparoscopy was performed, revealing a 1080° counterclockwise torsion of the left fallopian tube with necrosis, while the ovary appeared normal. As detorsion failed to restore color, a left salpingectomy was performed. Histopathology confirmed torsion secondary to hydrosalpinx. The postoperative course was uneventful, and the patient has remained symptom-free for one year. This case demonstrates that IFTT can occur even in adolescents without risk factors. Identifying a normal ovary on ultrasonography is crucial for suspecting IFTT, and early diagnostic laparoscopy is essential for confirming the diagnosis and preserving future fertility.