This copy is for personal use only. To order printed copies, contact [email protected] 609 WOMEN’S IMAGING Adnexal Torsion: Review of Radio- logic Appearances M. Taufiq Dawood, BSc, MBBS, MRCP, FRCR Adnexal torsion is the twisting of the ovary, and often of the fal- Mitesh Naik, BSc, MBBS, MRCP, lopian tube, on its ligamental supports, resulting in vascular com- FRCR promise and ovarian infarction. The definitive management is Nishat Bharwani, BSc, MBBS, MRCP, surgical detorsion, and prompt diagnosis facilitates preservation FRCR of the ovary, which is particularly important because this condi- Siham A. Sudderuddin, BSc, MBBS, tion predominantly affects premenopausal women. The majority MRCP, FRCR of patients present with severe acute pain, vomiting, and a surgical Andrea G. Rockall, MBBS, MRCP, abdomen, and the diagnosis is often made clinically with corrobora- FRCR tive US. However, the symptoms of adnexal torsion can be variable Victoria R. Stewart, BMedSci, BMBS, and nonspecific, making an early diagnosis challenging unless this MRCP, FRCR condition is clinically suspected. When adnexal torsion is not clini- cally suspected, CT or MRI may be performed. Imaging has an RadioGraphics 2021; 41:609–624 important role in identifying adnexal torsion and accelerating de- https://doi.org/10.1148/rg.2021200118 finitive treatment, particularly in cases in which the diagnosis is not Content Codes: an early consideration. Several imaging features are characteristic From the Department of Radiology, St Mary’s of adnexal torsion and can be seen to varying degrees across differ- Hospital, Imperial College Healthcare NHS ent modalities: a massive, edematous ovary migrated to the midline; Trust, Praed Street, London W2 1NY, England (M.T.D., M.N., N.B., S.A.S., A.G.R., V.R.S.); peripherally displaced ovarian follicles resembling a string of pearls; and Division of Cancer, Department of Surgery a benign ovarian lesion acting as a lead mass; surrounding inflam- and Cancer, Imperial College London, London, matory change or free fluid; and the uterus pulled toward the side England (N.B., A.G.R.). Presented as an educa- tion exhibit at the 2019 RSNA Annual Meeting. of the affected ovary. Hemorrhage and absence of internal flow or Received May 11, 2020; revision requested June enhancement are suggestive of ovarian infarction. Pertinent condi- 25 and received September 9; accepted Septem- ber 21. For this journal-based SA-CME activity, tions to consider in the differential diagnosis are a ruptured hemor- the author A.G.R. has provided disclosures (see rhagic ovarian cyst, massive ovarian edema, ovarian hyperstimula- end of article); all other authors, the editor, and tion, and a degenerating leiomyoma. the reviewers have disclosed no relevant relation- ships. Address correspondence to M.T.D. (e- mail: [email protected]). Online supplemental material is available for this article. ©RSNA, 2021 ©RSNA, 2021 • radiographics.rsna.org SA-CME LEARNING OBJECTIVES After completing this journal-based SA-CME activity, participants will be able to: Introduction Summarize the typical clinical manifes- Torsion is defined as the twisting of an organ or part of an organ tation of adnexal torsion. along its own axis (1). Torsion of the adnexa is a gynecologic emer- List the imaging features of adnexal gency that affects approximately 2%–3% of females who present torsion seen at US, CT, and MRI. with acute pelvic pain (2–4). Both the ovary and the fallopian tube Discuss important differential diag- typically are involved; hence, the preferred term adnexal torsion rather noses based on imaging appearances to than ovarian torsion (5). However, these terms are generally used avoid potential misinterpretations. interchangeably in clinical practice. The ovary and fallopian tube See rsna.org/learning-center-rg. twist on their vascular and ligamental supports, causing interrupted perfusion that is initially due to venous and lymphatic conges- tion and subsequently caused by compromise to arterial flow. Less commonly, torsion of the fallopian tube in isolation or torsion of extraovarian (paratubal or paraovarian) cysts also can occur. Despite being relatively uncommon, adnexal torsion is an important cause of morbidity, and its nonspecific manifestations can prove to be a diagnostic challenge. To avoid ovarian infarction and the possibility of associated subfertility, early detection is critical. 610 March-April 2021 radiographics.rsna.org TEACHING POINTS The massively enlarged ovary is often too big to be contained within the pelvis and thus migrates superiorly and toward the midline, usually lying in front of the uterus. This adnexal movement pulls the uterus out of its usual position and to- ward the side of the affected ovary. The altered position and relationship of the ovary and uterus are highly suggestive of adnexal torsion. Ovarian enlargement increases the tendency of the ovary to twist on its ligaments, and the presence of a benign ovarian Figure 1. Schematic diagram of the ovaries (Ov) and uterus lesion is the single greatest risk factor for adnexal torsion. (U). The left side of the image shows the normal relationships Nausea and vomiting occur in 70% of patients with adnexal among the structures attached to the ovary: suspensory liga- torsion; this is higher than the frequency with which these ment of the ovary (1), which contains the ovarian artery and symptoms manifest with other gynecologic causes of pelvic vein; broad ligament (2); ovarian ligament (3); and fallopian pain. When these symptoms are present, torsion should al- tube (4). The right side of the image shows how these relation- ways be considered as a likely diagnosis. ships change in the setting of adnexal torsion, with the twisted Although the findings of abnormal or reduced ovarian blood pedicle (arrow) consisting of the suspensory ligament and fal- lopian tube and resulting in a congested enlarged ovary. flow are sensitive for torsion, it is important not to be falsely reassured by normal vascularity, as arterial perfusion can be maintained until relatively late in the course of torsion. (also known as the infundibulopelvic ligament), The pedicle twist appreciated at US and MRI can be difficult to visualize on CT images. Rather, the thickened vascular pedicle which contains the ovarian artery and vein. can appear as elongated or triangular enhancing soft tissue Finally, the fallopian tube drapes over the broad at the anterolateral margin of the uterus, between the uterus ligament, attaching the ovary to the lateral wall and involved ovary. of the uterine fundus. The ovaries and fallopian tubes receive a dual blood supply from the ovar- ian and uterine arteries (7). The majority of patients present with severe In adnexal torsion, the ovary rotates on its axis acute pain, vomiting, and a surgical abdomen (ie, to cause a twist in the suspensory ligament that an acute intra-abdominal condition that requires contains the vascular pedicle (Fig 2, Movie 1). surgery). The diagnosis of adnexal torsion is often While adnexal torsion involves both the ovary made clinically with corroborative US. However, and the fallopian tube in up to 67% of cases because the symptoms are nonspecific, making an (8,9), isolated ovarian torsion also can occur, early diagnosis of adnexal torsion can be challeng- with sparing of the fallopian tube. However, ing unless the condition is clinically suspected. cases of isolated ovarian torsion are rare owing Imaging has a fundamental role in early identifica- to the wide attachment between the ovary and tion, particularly given its routine use in the acute the broad ligament (10). In practice, these two setting to triage patients with abdominopelvic pathologic entities are very challenging to distin- pain. Imaging features that support a diagnosis of guish with imaging alone, as both of them cause adnexal torsion must be correctly interpreted to a twisted vascular pedicle and secondary changes enable expeditious patient management. in the adjacent ovary. Isolated fallopian tube tor- In this article, we review the pathophysiology sion also has been described, with similar features of adnexal torsion, making reference to prin- of an adnexal twist but sparing of changes in the cipal anatomic features. We define the clinical ovary itself (11). manifestations of this pathologic entity, discuss The twist in the ovarian suspensory ligament the relative merits of different imaging modali- causes compression of the relatively low-pres- ties in the diagnosis, and review typical imaging sure ovarian vein and lymphatics, which become features. In addition, we highlight key differen- engorged, with massive enlargement of the ovary tial diagnoses to be considered during image and vascular pedicle. During this early period of interpretation and associated pitfalls that may ovarian expansion, the arterial supply is pre- cause confusion. served because arterial pressures are higher than venolymphatic pressures and owing to a more Anatomy and Pathophysiology muscular arterial vessel wall. Changes are re- In a premenopausal woman, the normal ovary versible during this time, and the ovary remains can measure up to 20 cm3 (6) and is held in place potentially salvageable. If left uncorrected, the by a series of ligamental supports (Fig 1). The arterial supply to the ovary can become compro- ovarian ligament attaches the ovary to the uterus. mised owing to marked luminal narrowing that The broad ligament, a broad-based peritoneal causes ischemia and subsequent infarction (10). fold, attaches the uterus to the pelvic sidewall The severity of vascular impairment depends on and encases the suspensory ligament of the ovary the degree of rotation of the adnexum about its RG • Volume 41 Number 2 Dawood et al 611 Figure 2. Adnexal torsion in a 41-year-old woman who presented with right-sided loin pain. (a) Focused transvaginal US image depicts an enlarged right ovary (RO) measuring 7 cm in length, with increased central echogenicity and normal follicles (arrowhead) within. (b) US im- age shows a whirlpool (curved arrow) with twisted hypoechoic vessels, which was confirmed as being continuous with the ovary and uterus at dynamic US assessment (see Movie 1).