Magnetic resonance imaging characteristics of deep endometriosis

The aim of this study was to describe magnetic resonance (MR) imaging findings in histopathologically proven deep endometriosis infiltrating the uterosacral ligaments, the pouch of Douglas, the rectum or the bladder. Twenty patients presenting with a clinical suspicion of deep endometriosis underwent preoperative MR imaging. Sagittal and axial fast T2- and axial T1-weighted spin echo MR sequences were performed. Four patients had post-contrast images. MR results, including morphology and signal intensity of each lesion, were compared to intraoperative gross appearance and histopathology. Histopathology diagnosed 24 lesions of deep endometriosis in the uterosacral ligaments (n = 12), the pouch of Douglas (n = 2), the rectum (n = 3), the bladder (n = 7). Uterosacral ligaments with deep endometriosis were statistically different from normal uterosacral ligaments for proximal nodularity (P = 0.001). There was no difference in signal intensity between normal and abnormal uterosacral ligaments. Contrast-enhanced SE images in four patients with detrusor invasion showed an interruption of the hypointense detrusor by the enhancing bladder endometriosis. Rectal endometriosis was missed in two of three patients and showed non-specific rectal wall thickening in one patient. It is concluded that MR imaging can diagnose deep endometriosis of uterosacral ligaments, the bladder and the pouch of Douglas, but lacks sensitivity in detecting rectal endometriosis without rectal distension.