Clinical History
A previously healthy 36-year-old woman presented with intense lower abdominal pain. At clinical examination there was tenderness in the lower part of the abdomen. A large mass was present in the left lower quadrant. Bleeding was suspected: low BP (115/60 mm Hg), tachycardia (120 bpm) and low haemoglobin (4.9 mmol/l).
Imaging Findings
Contrast-enhanced CT of the abdomen was performed (single-phase, 70 seconds after injection). A large rounded solid mass measuring 15 x 16 x 17 cm was seen in the central and left parts of the abdomen (Figs. 1 and 2). It had smooth margins and heterogeneous contents. There was no contact with the kidneys, small intestine, colon or uterus. A small contrast-enhancing structure (the fallopian tube) was seen connected to the lower pole of the mass (Fig. 2a), suggestive of the mass being an enlarged right ovary with torsion (adnexal torsion). The heterogeneous content was likely to be caused by bleeding. Free intraperitoneal fluid was also present. The left ovary and uterus were in their normal positions and appeared normal (Fig 2b).
The patient underwent emergency surgery, and the diagnosis of 180 degrees torsion of the right adnex was confirmed. Pathology showed ovarian fibroma with haemorrhage. No malignancy.
Discussion
Ovarian torsion is defined as complete or partial rotation of the ovarian vascular pedicle on its long axis. Usually it involves both the ovary and the fallopian tube, thus the term 'adnexal torsion' is preferred to 'ovarian torsion' [1]. Torsion causes obstruction to the arterial inflow and venous outflow from the ovary. Adnexal torsion is a gynaecological emergency requiring surgery.
Adnexal torsion primarily affects premenopausal women, and is more common on the right than left side, as the right utero-ovarian ligament usually is longer on the right side [2, 3]. The most important predisposing factor for torsion is presence of an underlying adnexal mass like mature teratoma [4, 5]. However, other ovarian lesions may also predispose to torsion. Theoretically malignant lesions with ingrowth to other organs will prevent torsion [5]. Other predisposing factors include long ovarian ligaments, hyper stimulation for in vitro fertilisation, polycystic ovaries, and laparoscopic hysterectomy [1]. The present case confirmed some of the predisposing factors: The patient was premenopausal and had a large ovarian mass. Furthermore torsion occurred on the right side.
The diagnosis of adnexal torsion is often clinical, aided by ultrasound [5]. However, as the clinical presentation can mimic other causes of acute abdominal pain, CT is occasionally performed, like in the present case. CT findings of adnexal torsion includes adnexal enlargement, well-defined smooth margins of the torsed adnexa, cystic components within the adnexa, ascites, and abnormal location of the involved adnexal structure [5]. Besides cystic adnexal components, all of the listed CT findings were present in the current case.
Ultrasound features of adnexal torsion include a unilateral enlarged ovary, peripheral cystic structures, free peritoneal fluid, a coexistent mass within the involved ovary, and lack of flow with Doppler ultrasound [4].
Adnexal haemorrhage has previously been described in cases with adnexal torsion [6]. It may be difficult to detect this with contrast-enhanced CT [5]. However, in the present case the very heterogeneous contents of the large adnexal mass was supportive of the diagnosis.
In conclusion, adnexal torsion may be a cause of acute abdominal pain. Common CT findings of this condition are an enlarged ovary with an abnormal location combined with free peritoneal fluid.
Differential Diagnosis List
Adnexal torsion
Mesenteric sarcoma
Ovarian carcinoma
Ectopic pregnancy
