MRI for Endometriosis
Dr Livia Stanciulescu
Wellborn Endometriosis Centre
The examination of MRI in endometriosis is dedicated especially to the preoperative evaluation of deep endometriosis and complements the clinical and ultrasound examination. A qualitative examination should provide the surgeon with a more detailed map of the lesions, and begins with good communication between the gynaecologist and the imaging doctor and continues with a more detailed discussion between the imaging doctor and the patient.
Knowing the patient’s symptoms is of real use in guiding the examination protocol. Intravaginal and intrarectal gel instillation relax the cavities, thus leading to better visualisation of the walls and possible endometriosis nodules, with the possibility of evaluating the depth of the infiltration zone. By contrast offered by the gel, a better delineation of the peritoneal recesses (recto-vaginal and bladder-vaginal recession) is obtained. Also, the presence of gel reduces peristaltic artifacts.
The MRI ovarian endometriomas appearance is that of the cyst in the hypersignal in the T1 weight (bright white) and the hyposignal in the T2 weight (different shades of grey, determined by the presence of hemoglobin degradation products, in different stages).
Endometriotic nodules appear as a mass with infiltrative characters, spiked contour, with very low signal in T2 weighting, frequently with hyperintense cystic inclusions in T1 weighting, causing adhesions and retractable effect on the adjacent structures. The recto-vaginal septum requires special attention, lesions at this level are being frequently underdiagnosed.
For intestinal endometriosis, the role of the MRI exam is to preoperatively evaluate the depth of endometriotic infiltration, nodules that affect the muscularis propria and have an indication for resection. The distorted appearance of the digestive wall is a good indicator for infiltration of the muscular layer. The degree of stenosis is approximately appreciated, the rectal ampulla being a cavity organ whose maximum degree of repletion cannot be reproduced only with the help of gel instillation. An almost circumferential arrangement of the lesion is a criterion for a high degree of stenosis.
For urinary tract endometriosis the MRI examination, apart from detection, aims to assess the depth of endometriotic infiltration. If the pelvic ureters appear dilated, it should be mentioned in the written report, which may be a consequence of direct endometriotic infiltration or pelvic adhesion syndrome. The uterus-bladder recess is another frequently missed localization, often due to a maximal replenishment of the bladder or an exaggerated anteversion of the uterus, which may mask any lesions.
Uterine adenomyosis is a pathology commonly associated with endometriosis, but not only, but it may also accompany the presence of leiomyomas, hyperplasia or endometrial polyps. It has an MRI expression a thickening above the accepted normal limit (12 mm) of the myo-endometrial junction, frequently with included microcystic glandular dilations and irregular contour. It may have a diffuse or focal nodular appearance, sometimes polypoid, procident in the uterine cavity. The junctional area is influenced by the period of the menstrual cycle. It increases considerably in thickness during the menstrual period. To avoid a false-positive diagnosis, the time indicated for examination is the late proliferative phase.