Objective: Abdominal wall endometriosis is a rare subtype of extra-pelvic endometriosis; and the patients present with a painful abdominal mass that is particularly aggravated by menstruation. Ultrasound and MRI are the recommended diagnostic tools for the evaluation of the mass lesions. Biopsy is performed when calcifications in the granulation tissue cannot be differentiated from chronic blood products. Susceptibility weighted imaging (SWI) is a relatively new MR technique where the image contrast is mainly based on magnetic susceptibility differences. SWI has higher sensitivity to blood products compared to conventional MRI sequences. Although it has been mostly used in neuroimaging studies, recent studies have shown that it provides additional diagnostic information abdominal imaging. In this article, we aim to demonstrate the diagnostic utility of SWI for lesions of abdominal wall endometriosis.
Case: A 29-year-old woman with a history of Caesarean-section delivery five years ago presented with a cyclic pain and slowly growing abdominal mass located superior to the Caesarean incision scar on the left side of the midline. A heterogeneous hypoechoic solid mass was detected ultrasonographically underneath the fascia of rectus muscle. On MRI, a solid heterogeneous enhancing lesion located anterior to the rectus muscle was seen in which blood products and calcifications could not be differentiated by their signal intensities. On SWI sequence, signal voids within the lesion on magnitude images were hyperintense on phase images and this excluded calcifications endorsing endometriosis as diagnosis.
Conclusion: SWI imaging with its high sensitivity to blood products, contributes to the diagnosis of abdominal wall endometriosis by depicting different phases of hemorrhage during menstruation and non-menstruating days. Another advantage of SWI is the ability to differentiate between blood products and calcification which provides additional value to improve diagnostic ability of pelvic MRI.
Key words: Abdominal wall endometriosis, Magnetic resonance imaging, Susceptibiliy weighted imaging, scar, endometriosis
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