Appearance of abdominal wall endometriosis on MR imaging

Objective Abdominal wall endometriosis (AWE) is defined as endometrial tissue that is superficial to the peritoneum. AWE is often difficult to diagnose, mimicking a broad spectrum of diseases. The aim of this study was to describe the appearance of AWE on magnetic resonance (MR) imaging. Methods We present ten patients with AWE (12 lesions) in which MR imaging was used for diagnosis. MR imaging included T2-weighted imaging and T1-weighted imaging with fat suppression. To assess the value of diffusion-weighted imaging (DWI) in endometriosis, four patients underwent additional DWI. The apparent diffusion coefficient (ADC) was calculated using b values of 50, 400, 800 and 1,200 s/mm 2 . Results In most cases, the lesion was located ventral or dorsal to the aponeurosis of the rectus oblique muscle ( n = 6) or in the rectus abdominis ( n = 5). MR of AWE lesions showed isointense or slightly hyperintense signal compared with muscle on T2-weighted images and showed isointense or slightly hyperintense signal compared with muscle on T1-weighted images with foci of high signal intensity, indicative of haemorrhage. The mean ADC value of AWE was 0.93 × 10 –3 /mm 2 /s. Conclusion MR imaging seems to be useful in determining the location and depth of infiltration in surrounding tissue preoperatively.