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Objective:
Isolated fallopian tube torsion (IFTT) is a gynecological emergency characterized by independent rotation of the fallopian tube on its own axis, leading to restricted blood flow and potential infarction. Conventionally, this is known as a rare diagnosis that is difficult to detect on imaging due to the absence of specific features. The diagnosis is often unclear until persistence or progression of symptoms necessitate a diagnostic laparoscopy that reveals an IFTT. ­Although detorsion is attempted, oftentimes delayed diagnosis results in salpingectomy. Locally, three cases of surgically proven IFTT were diagnosed over a period of only 1 month, which sparked our interest and hypothesis that this entity might be more common but under-diagnosed due to radiologists’ lack of familiarity with its imaging appearance on various modalities. Therefore, a comprehensive literature review was performed, with imaging and pathological findings analyzed.

Materials and Methods:
We conducted a retrospective study of three cases of IFTT with preoperative ultrasound, CT, and MRI demonstrating patterns of IFTT. Imaging appearances were correlated with observations during surgery and pathology records. Furthermore, we searched the PubMed electronic database for English articles meeting the criteria of "(Fallopian tube) AND (Torsion) AND (Isolated)". Articles that included associated ovarian torsion were excluded. Overall, 67 articles were excluded, and 135 articles between 1995 - 2023 were analyzed.

Results:
Our analysis included 184 patients across case reports, case series, and retrospective reviews. The average age was 24.2 ± 14.0 years. Nearly 100% of the patients presented with abdominal pain, and 44% had associated nausea or vomiting. Forty-three percent endorsed pain over the right lower quadrant, 23% over the left lower quadrant, and the remaining described nonspecific lower abdominal pain. On imaging (primarily ultrasound), 54% of cases had an adnexal cyst, and 32% had hydrosalpinx. A whirlpool sign, “beaked” ends of the fallopian tube, and a “double ovary” sign were specific signs for IFTT. CT and MRI were beneficial in diagnosing IFTT in 13% and 56% of the cases. IFTT was prospectively diagnosed on imaging in 18% of cases; the majority were only recognized at surgery. During surgery, a twisted fallopian tube with hematosalpinx, edema, or infarct at the distal end was often observed, which was congruent with pathology. Overall, 36% of the patients underwent detorsion while the remaining 64% had salpingectomy.

Conclusion:
IFTT is an under-recognized condition on imaging, and timely diagnosis is critical to maintain viability of the fallopian tube. Therefore, understanding the specific imaging findings, such as the whirlpool sign of the fallopian tube or the double ovary sign in the presence of an adnexal cyst or hydrosalpinx, are important for early and accurate detection. CT and MRI may have a role in identifying torsion when ultrasound is inconclusive. Ultimately, the diagnostic imaging workflow must be complemented by clinical assessment and ruling out more common etiologies.