Ovarian torsion: incremental role of contrast-enhanced ultrasound

Background

Adnexal torsion is a gynaecological surgical emergency.1 Preoperative diagnosis of ovarian torsion along with information regarding viability is important from the surgical point of view, as in the absence of a grossly necrotic ovary, intraoperative untwisting of the adnexa can be performed for ovarian salvage without significant risk of thromboembolism. Haemorrhagic infarction or gangrene, however, requires surgical removal without any attempt to untwist the ovarian torsion.2

Ultrasound (USG) along with colour Doppler ultrasound (CDUS) is the first-line imaging modality for the evaluation of suspected ovarian torsion; however, it has the following limitations. It is highly operator dependent, colour Doppler cannot detect slow flow or may pick up false signal from tissue movement. Besides, the spontaneous torsion and detorsion of ovary can produce variable patterns of Doppler flow which makes definitive diagnosis even more difficult. Even the established USG/CDUS signs suggestive of ovarian torsion do not always allow for a definitive diagnosis.3 Contrast-enhanced ultrasound (CEUS) is an excellent technique which overcomes these limitations. It determines an organ’s vascular supply since the contrast agent is purely intravascular and provides information regarding the parenchymal perfusion, resulting in a reliable diagnosis of ovarian torsion along with information about the ovarian parenchymal viability, similar to contrast-enhanced CT and MRI.4 5 Thus, CEUS allows accurate and timely diagnosis, serving as a useful supplementary imaging modality with the added advantage of lack of ionising radiation.

Case presentation

A woman in her 20s presented in the emergency with sudden onset, severe, intermittent lower abdominal pain for 1 week. She had no gastrointestinal or genitourinary complaint. She had normal, regular menstrual cycles and her last normal menstrual period was 10 days back. She did not have any significant medical or surgical history. On general physical examination, she had normal vitals; however, there was severe pallor. Her pelvic examination revealed a large, palpable, tender, immobile pelvic mass of size approximately 10×10 cm.

Investigations

The laboratory parameters at the time of presentation revealed neutrophilic leucocytosis, anaemia (haemoglobin 3.5 g/dL), elevated ESR (erythrocyte sedimentation rate) and C reactive protein.

She underwent a transabdominal B-mode USG evaluation initially on Supersonic Imagine Aixplorer equipment using a curvilinear probe by an experienced radiologist. It revealed a large, thick-walled, right ovarian cyst with no obvious septations or solid component (figure 1A) and peripherally displaced ovarian follicles, located in midline in the pelvis and cranial to the uterine fundus. The right ovarian pedicle appeared thickened. The left ovary was well visualised. Colour Doppler was also performed which did not reveal any vascularity within the thick walls of the cyst (figure 1B). Transvaginal USG was not performed as the patient was an unmarried female and refused to give consent for the same. The patient had already undergone a CECT Abdomen prior to presentation at our institution. This CT scan had revealed a large, midline, adnexal cystic lesion measuring approximately 10×8 cm with eccentrically thick, hyperattenuating wall on non-contrast scan and equivocal wall enhancement (figure 2). To evaluate the ovarian parenchyma vascularity and viability, we proceeded to CEUS.

The patient was screened for contraindications for SonoVue, including a history of allergies to sulphur hexafluoride or other components, left-to-right shunt congenital heart disease, severe pulmonary hypertension, uncontrolled hypertension, adult respiratory distress syndrome and pregnancy or breastfeeding. A written informed consent for the procedure was obtained.

CEUS was performed on the same equipment (Supersonic Imagine Aixplorer). Intravenous access was established in the antecubital fossa (antecubital vein) using a 20G cannula with a 3-way connector. The ultrasound contrast agent (UCA) Sonovue was reconstituted (25 mg of lyophilised sulphur hexafluoride powder in 5 mL normal saline) as a soluble agent 5 min before starting the study and agitated well to generate microbubbles. The right adnexal cyst was focused on B-mode USG and the field of interest was maintained, followed by switching on the CEUS mode in dual window setting to allow simultaneous display of tissue and contrast signals on the monitor. Meanwhile, 2.4 mL Sonovue bolus was administered intravenously followed by flushing with 10 mL normal saline. The right adnexal cyst wall vascularity was assessed in real time by continuous scanning and simultaneous acquisition of images till 300 s (5 min) post UCA administration.

The patient was observed in the emergency room following the procedure for duration of half an hour for possible adverse reaction caused by the UCA. She did not show symptoms or signs of any adverse reaction.

Treatment

In view of the non-viable ovarian tissue, the patient underwent surgical removal of the right ovary and fallopian tube. The per operative findings were consistent with the imaging findings which showed a thick-walled cyst with multiple twists in the pedicle (figure 4). Intraoperative frozen sections and subsequent histopathology findings of the right ovarian cyst revealed ovarian tissue with haemorrhagic necrosis and dystrophic calcification, consistent with torsion. Sections from the fallopian tube also showed haemorrhagic necrosis.

Written informed consent was obtained from the patient for the publication of this case report, including accompanying images.

Outcome and follow-up

The patient is stable on follow-up visits with no abdominal pain and normal menstrual cycles. She returned to her daily normal activities within 2 weeks of surgery and is currently asymptomatic.