Ovarian torsion is a medical emergency that involves the twisting of an ovary, and sometimes the fallopian tube, around its supporting ligaments. This twisting can disrupt the organ’s blood supply, potentially leading to tissue damage. Ultrasound imaging plays a significant role in evaluating individuals suspected of having this condition. This article explains what medical professionals look for on ultrasound when ovarian torsion is suspected.
What is Ovarian Torsion?
Ovarian torsion occurs when an ovary, and often the fallopian tube, twists around its supporting ligaments. This twisting compresses the blood vessels within these ligaments, impeding blood flow to the ovary. This can lead to a reduction in oxygen and nutrients.
Initially, the twisting obstructs thinner-walled veins and lymphatic vessels, hindering blood from leaving the ovary. This blockage causes blood to pool, leading to swelling and congestion. If the twisting persists, the thicker-walled arterial supply can also become compromised, completely cutting off blood flow. Prolonged lack of blood supply can result in tissue death and potential loss of the affected ovary.
Key Ultrasound Indicators of Ovarian Torsion
An enlarged, swollen ovary is a common ultrasound finding, often appearing more globular than its typical shape. This enlargement, frequently exceeding 4 cm in diameter, results from fluid accumulation due to obstructed venous and lymphatic drainage. The internal tissue of the affected ovary may also appear less uniform or more dense than a healthy ovary, reflecting this fluid buildup and potential hemorrhage.
Displacement of ovarian follicles or cysts towards the periphery of the enlarged ovary is another visual cue. As the ovary swells with fluid, it pushes these smaller, fluid-filled sacs to the outer edges. This creates a characteristic “string of pearls” or “follicular ring” appearance along the rim. Follicles may also be surrounded by a thick, bright rim, indicating fluid and congestion.
Doppler flow analysis assesses blood movement within ovarian vessels. In ovarian torsion, there is often reduced or absent blood flow to the affected ovary. Venous blood flow, which carries blood away, is typically obstructed first due to lower pressure. While arterial flow may initially remain present, its absence indicates a more severe twist. The presence of some blood flow on Doppler ultrasound does not completely rule out torsion, as the ovary has a dual blood supply and flow can sometimes be preserved or be intermittent.
A specific sign of ovarian torsion is the “whirlpool sign,” referring to the appearance of the twisted vascular pedicle. This sign is observed when the blood vessels and supporting ligaments supplying the ovary are seen coiled or twisted, resembling a whirlpool. This twisting can be visualized directly on grayscale ultrasound or with color Doppler, showing the swirling pattern of blood flow. Identifying this sign provides strong evidence for diagnosis.
Free fluid in the pelvic cavity, particularly around the affected ovary, can also accompany ovarian torsion. This fluid may result from congested and leaking blood vessels within the twisted ovary. While not exclusive to ovarian torsion, its presence alongside other suspicious ultrasound findings can support the diagnosis.
The Role of Clinical Symptoms in Diagnosis
While ultrasound provides visual evidence, ovarian torsion diagnosis combines these findings with clinical symptoms. Patients often experience sudden, severe pelvic pain, which can be sharp or crampy and may radiate to the back or thigh. This pain is typically localized to one side of the lower abdomen, though it can sometimes be more generalized.
Nausea and vomiting frequently accompany the pain. While not specific to ovarian torsion, these symptoms, when abrupt and severe, raise suspicion. Sometimes, the pain can be intermittent, occurring if the ovary partially twists and untwists.
Prompt medical evaluation is important if ovarian torsion is suspected, given the potential for rapid tissue damage. Even if initial ultrasound findings are not entirely clear, clinical suspicion based on symptoms can guide medical action. Combining characteristic pain, associated symptoms, and supportive ultrasound findings allows for timely diagnosis and intervention.