British Journal of Radiology (2006) 79, e208-e210
© 2006 British Institute of Radiology
doi: 10.1259/bjr/23068987
A case of torted parafimbrial cyst on MRI: case report and review of the literature
K Gopal, FRCR
1
Y Lim, FRCR
1
M Dobson, FRCR
1
P Keating, FRCS
2 and
H Stringfellow, MRCP (Path)
3
Departments of 1 Radiology, 2 Gynaecology and 3 Pathology, Royal Preston Hospital, Sharoe Green Lane, Preston PR2 9HT, UK
Correspondence: Dr Mike Dobson, Lancashire Teaching Hospitals NHS Trust, Royal Preston Hospital, Sharoe Green Lane, Fulwood, Preston, PR2 9HT, UK. E-mail: mike.dobson{at}lthtr.nhs.uk
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Abstract
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Para-ovarian cysts (POCs) are an occasional finding at surgery, although they are rarely appreciated on imaging studies. Accurate diagnosis depends upon the demonstration of a para-ovarian location. We present the MR appearances of a torted POC in a fimbrial location, resembling a dermoid cyst.
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Introduction
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Para-ovarian cysts (POCs) represent approximately 10% of adnexal masses [1]. They are usually small and asymptomatic, although are occasionally large, resulting in pelvic pain [2]. POCs usually arise in the broad ligament and are thin walled and unilocular. Multilocular cysts may resemble ovarian serous cystadenomas [3]. It may be difficult to reliably differentiate a POC from an ovarian cyst by imaging [1]. Therefore, they are often removed surgically, especially if they contain solid tissue. Laparoscopic cystectomy would be indicated for a large or symptomatic POC or a conservative approach for a smaller asymptomatic lesion. [4]. We present a case of parafimbrial cyst, which displayed features suggestive of a dermoid cyst.
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Case report
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A 19-year-old female presented with a 7-day history of menorrhagia and left pelvic pain. Clinical examination and routine blood tests were normal. Transabdominal ultrasound showed a septated, cystic left adnexal lesion containing mural nodularity (Figure 1
). MR was arranged for further evaluation. This demonstrated a well-defined, left adnexal cyst, which returned high signal on T1 and T2 weighted images (Figure 2a,b). There was a minor amount of signal reduction on an axial short tau inversion recovery (STIR) sequence (Figure 2c). In addition, there was extensive linear stranding and an eccentric mural nodule, features suggesting a dermoid cyst (Figure 2). It was noted that both ovaries did, in fact, appear normal, and therefore the provisional diagnosis of a pedunculated dermoid was made.
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Figure 2. (a) Axial T1 weighted sequence showing a predominantly high signal cystic left adnexal lesion (arrow). (b) Axial T2 weighted sequence. The cyst (arrow) contents returns high signal, in addition to which, there was also extensive linear stranding and an eccentric mural nodule. Note that both ovaries appear normal (arrowheads). (c) Axial short tau inversion recovery (STIR) showing minor suppression of signal within the cyst.
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Her pain did not settle and she therefore underwent a laparotomy. At laparotomy a torted, gangrenous parafimbrial cyst with adhesion to the pelvic side-wall and distension of the left Fallopian tube was noted. She underwent simple cyst removal and settled uneventfully. Histology confirmed the diagnosis. The cyst contained altered blood product, which explained the signal characteristics on MRI.
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Discussion
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POCs are well recognized by gynaecologists, although rarely diagnosed by radiologists who are usually unaware of such an entity. They commonly arise in the broad ligament, especially in the mesosalpinx between the ovary and the Fallopian tubes. Histologically, they are divided into three categories: mesothelial (peritoneal inclusions), paramesonephric (as in this case) or mesonephric [5].
These cysts are usually small, although they may vary in size. Larger cysts are found in younger patients and are usually of mesothelial origin [5]. They may be symptomatic due to their size, or due to torsion, haemorrhage or rupture. Malignancy has been reported in 2–3% of cases [6], although this is rare in lesions smaller than 5 cm [7]. POCs are usually single, but bilateral lesions have been reported [5, 8]. The differential diagnosis includes: functional cysts in young patients – these show fluctuation in size on follow up; peritoneal inclusion cysts – these are often large and related to pelvic adhesions due to previous pelvic surgery or pelvic inflammatory disease or endometriosis [9]; hydrosalpinx; – this should have a tubular configuration; endometriomas should also be included in the differential. Indeed, the cyst in our case contained altered blood.
Most POCs appear as simple cysts with a thin, smooth inner wall on ultrasound scanning [10]. Low-level internal echoes indicate previous haemorrhage into the cyst. Mural nodularity or thick septa would suggest a para-ovarian cystadenoma [11]. Demonstration of a simple POC clearly separate from the ovary should allow for conservative or minimally invasive treatment. Larger or more complex POCs may require excision. However, as they are rarely malignant, excision is generally done by laparoscopic cystectomy. A complicated ovarian cyst has a higher incidence of malignancy and may require a formal laparotomy. A confident pre-operative diagnosis of POC therefore has implications for patient counselling and management.
There have been only a few reports describing MR appearances of POCs [3, 9, 12], none of which were parafimbrial (as in our case). Uncomplicated POCs are usually unilocular and return low signal on T1 weighted images and high signal on T2 weighting. The tube and the ovary may be stretched over the cyst wall, though the ovary should be definable as a separate structure. This is an important MR feature in the diagnosis of POCs, although most other MR features are non-specific [3]. The high signal on T1 and T2 weighted sequences in our case suggested a dermoid cyst, although there was only minor signal reduction on the STIR sequence. This might have also suggested an endometrioma. A dermoid cyst may have been more specifically excluded using a fat suppression sequence rather than STIR, which is a rather more non-specific "fat-nulling" sequence.
In conclusion, we should like to draw attention to the diagnosis of POCs. Careful evaluation of pelvic MR images with appropriate sequences should allow a confident prospective diagnosis to be made by virtue of a POC being clearly separable from the ovary. This is important in terms of radiological accuracy and may also have implications for patient management.
Received for publication September 5, 2005.
Revision received February 2, 2006.
Accepted for publication February 6, 2006.
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References
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Abstract
Introduction
