Adnexal torsion: contribution of MR imaging in diagnosis

Clinical History

A 22-year old woman was admitted for acute pain in the right lower abdominal quadrant. Laboratory analysis showed mild leukocytosis and slight elevation of C-reactive protein. Transvaginal sonography revealed a complex right adnexal mass and a moderate amount of fluid in the Douglas pouch. A pelvic MR study was indicated.

Imaging Findings

MR imaging of the pelvis revealed right adnexal enlargement with the coexistence of a cystic mass, both not enhancing after contrast material administration (Figure 1). The lesion was entirely cystic, with signal intensity similar to that of water (Figure 1a-d) and free diffusion (Figure 1f), without solid components. The ipsilateral fallopian tube was thickened, slightly hyperintense on T1-weighted images and extremely hypointense on T2-weighted images, findings suggestive for acute hemorrhage (Figure 1a-d). Acute hemorrhagic parts caused a dramatic signal drop in the area on diffusion-weighted images, due to T2* effect and had no measurable ADC values (Figure 1f). Imaging findings were strongly suggestive of hemorrhagic necrosis of the adnexa following torsion and were confirmed surgically and pathologically (Figure 2, 3). The cystic mass proved to correspond to ovarian cystadenofibroma on histology.

Discussion

Background
Adnexal torsion is a rare cause of lower abdominal pain, often presenting as a diagnostic problem due to the nonspecific clinical, laboratory and sonographic findings, as it was seen also in this patient [1-7]. It is associated with an ipsilateral ovarian tumour or cyst in 50-81% of cases, which is almost always benign, in our case proved to represent an ovarian cystadenofibroma on pathology [1-7]. Early diagnosis is mandatory, allowing a conservative, ovary-sparing surgery in young women.
Imaging perspective
The sonographic findings of adnexal torsion are usually nonspecific and include the presence of a cystic, solid or complex adnexal mass, as it was seen in this patient [8-11]. Free intraperitoneal fluid is found in one to two thirds of patients. The most suggestive sonographic sign is the presence of multiple spherical cystic structures, up to 25 mm in diameter at the periphery of an enlarged ovary [8-11]. However, this sign may be a normal finding in a young fertile woman. The value of colour Doppler sonography in the diagnosis of adnexal torsion is under dispute. Normal adnexal blood flow may be seen in almost half of the patients with torsion.
CT and MR imaging is usually recommended in subacute or chronic cases to confirm the diagnosis of adnexal torsion and to differentiate haemorrhagic from nonhaemorrhagic infarction [1-4]. Common CT and MR imaging findings of adnexal torsion include fallopian tube thickening, ascites and uterus deviation to the twisted side, all met in this case. Tube thickening or a twisted vascular pedicle is considered as the most specific finding, related to the presence of congestion and oedema with or without haemorrhagic infarction of the tube. It also indicates a twisted oedematous pedicle, connecting the lesion with the uterus and engorged blood vessels [1]. Imaging findings suggestive of haemorrhagic infarction include eccentric smooth wall thickening exceeding 10 mm in a cystic ovarian mass, lack of contrast enhancement of the internal solid component or the thickened wall of a twisted adnexal mass, haemorrhage within the tube or adnexal mass, or haemoperitoneum [1-4]. Differentiating haemorrhagic from nonhaemorrhagic infarction due to adnexal torsion is extremely important for treatment planning, allowing a more conservative approach in cases of nonhaemorrhagic infarction [1]. Lack of contrast material enhancement and the presence of acute haemorrhage within the thickened tube suggested hemorrhagic infarction in our case, as proved subsequently on histopathology.

Differential Diagnosis List

Final Diagnosis

Adnexal torsion with haemorrhagic infarction.

URL:	https://www.eurorad.org/case/9280
DOI:	10.1594/EURORAD/CASE.9280
ISSN:	1563-4086