Isolated fallopian tube torsion is extremely rare; the preoperative diagnosis is challenging. Pregnancy complicates the pain localization as the intra-abdominal organs are displaced by the enlarged uterus. Here, we report a case of isolated fallopian tube torsion in the third trimester of pregnancy, which was successfully diagnosed with laparoscopy and unnecessary early termination of pregnancy was prevented. A 33-year-old woman, gravida 3 para 3, was referred to our hospital with a complaint of persisted severe right lower abdominal pain at 33 weeks of gestation. On physical examination, tenderness at the inside of the right anterior superior iliac spine was noted. Trans-abdominal ultrasonography revealed a cystic structure with solid mass, measuring 5.3 × 3.3 cm, at the point where tenderness was elicited. Because of the unremarkable past gynecological history and the pain localization, it was difficult to consider ovarian tumor pedicle torsion or degeneration of myoma. Therefore, diagnostic laparoscopy was performed, which revealed isolated right fallopian tube torsion. Therefore, she underwent laparoscopy-assisted right salpingectomy. The patient recovered fully, her pregnancy progressed well, and she delivered a healthy female baby at 36/5 weeks of gestation. It is necessary to suspect the possibility of isolated fallopian tube torsion when a cystic lesion is detected on trans-abdominal ultrasonography. Although the availability of an adequate field of surgery with laparoscopy is difficult in late pregnancy, laparoscopy is useful for determining the differential diagnosis of acute abdomen even in pregnant patients. Further studies are needed to determine the exact criteria for laparoscopic surgery during pregnancy.
