Magnetic Resonance Imaging (MRI’s) and endometriosis

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Surgery is the only method for definitive diagnosis of endometriosis; however, magnetic resonance imaging (MRI’s) can be used for preoperative planning as well as ruling out other related conditions. It is important to have a team who knows the correct protocol for imaging and for reading the images.

In this study, you will find correlations between MRI findings and surgical confirmations. The authors also discuss the best way to get the best images. Please follow the link for more information and for associated images. 

“Diagnostic imaging is necessary for treatment planning. MRI is as a second-line technique after ultrasound. The MRI appearance of endometriotic lesions is variable and depends on the quantity and age of haemorrhage, the amount of endometrial cells, stroma, smooth muscle proliferation and fibrosis. The purpose of surgery is to achieve complete resection of all endometriotic lesions in the same operation.” Preparing for the MRI: “In preparation for imaging, it is recommended that patients fast (4–6 h) before the examination. Bowel preparation includes an enema administered approximately 2–3 h before the examination. The study should not be conducted during the menstrual cycle. MR imaging is performed with moderate repletion of the patient’s bladder, since an overfilled bladder may cause detrusor contractions and may obliterate the adjacent recesses thus compromising the identification of small parietal nodules [12]. On the other hand, an empty bladder prevents optimal visualization of the ureters. MR imaging is performed with the patient lying in the supine position (entry position feet first). In patients who show a dilatation of the excretory system, the urographic phase is acquired in the prone position. In claustrophobic patients, prone position may reduce anxiety and improve exam acceptability. When the clinical evaluation suggests a rectosigmoid endometriosis, rectal opacification is performed before the examination. Retrograde distension of the rectum and the sigmoid colon is obtained inside the gantry with a rectal enema of 750 mL of saline solution introduced through a Nelaton catheter (20 Ch, 6.67 mm × 360 mm). Bowel cleansing is performed through oral administration of a polyethylene glycol solution (1000 mL) the day before the study. In these patients the intravenous administration of an antispasmodic agent, scopolamine-N-butyl bromide (Buscopan® 20 mg; Boehringer Ingelheim, Milano, Italy) just before image acquisition is mandatory to reduce motion artefacts caused by bowel peristalsis. Even if rectal opacification is not strictly necessary to detect endometriotic lesions of the intestinal wall, rectal distension may be useful to evaluate the degree of bowel stenosis.”Conclusions: “Endometriosis is a chronic condition affecting women during the reproductive lifespan. Diagnosis of endometriosis must take into account clinical symptoms, physical examination, laboratory tests and different imaging techniques. Since pelvic anatomy is complex and may vary with distortion by invasive endometriosis, the radiologist must be aware of both normal and deranged anatomy.“The ideal purpose of surgery is a therapeutic and effective intervention based on a careful preoperative evaluation. From this point of view, the role of MR imaging to help diagnose and plan surgical strategy is critical in the management of the disease. Preoperative detection of all endometriotic lesions is recommended to choose the surgical approach and to plan a multidisciplinary team work [29]. This multidisciplinary approach including radiologists, gynaecologists, urologists, gastrointestinal surgeons, and (in selected cases) neurosurgeons, is recommended to improve diagnostic imaging accuracy and patients’ outcome, and to reduce postoperative complication rates. The recent awareness that endometriosis may be medically treated based on strong clinical suspicion [57] and that laparoscopy should be intended for surgical treatment, not for diagnostic purposes [58], furtherly enhance the role of non-invasive diagnostic procedures and particularly of MR imaging.“In any case, due to the complexity of the disease, it is appropriate to centralize the overall care of endometriosis patients to reference centres in order to pursue a patient-centred approach tailored to the patient’s specific condition and desires.”

In this study, you will see more information on the best techniques for performing the MRI as well as what to look for on the MRI findings. Please follow the link for more information as well as images. 

Technique: “A dedicated MRI protocol is essential for identification of disease and surgical planning. MRI imaging at 3 Tesla is preferred due to superior resolution….Administration of intravenous contrast is important, as areas of mural nodularity or solid components may exist within an ovarian lesion, and is essential to differentiate endometriomas from other cystic neoplasms….Rectal and vaginal gel help optimize visualization of endometriosis deposits on the vaginal and rectal wall.”Superficial endometriosis: “Superficial endometriosis is often not detectable with MRI or ultrasound.”Endometriomas: “On MRI, ovarian endometriomas have a characteristic homogeneous T1W hyperintensity and a relatively low T2W signal intensity. There can be heterogeneity to the T2W hypointensity, called T2W “shading”, caused by blood products in various stages of degradation from multiple episodes of bleeding. A more specific sign in the diagnosis of ovarian endometriomas is the “T2 dark spot sign,” defined as discrete markedly hypointense foci within the cyst on T2-weighted images, with or without T2 shading. In distinguishing ovarian endometriomas from non-endometrioma hemorrhagic cystic lesions, a study has shown T2 shading to have a 93% sensitivity, 45% specificity, 72% positive predictive value (PPV) and 81% negative predictive value (NPV), while T2 dark spots had a 93% sensitivity, 45% specificity, 72% PPV and 81% NPV (Figure 2).7”Deep Infiltrating Endometriosis (DIE): “Occasionally small foci of T2W hyperintensity representing the ectopic endometrial glands can be seen.9 This solid type of endometriosis may be harder to identify on MRI, however, postcontrast, these lesions demonstrate delayed enhancement similar to fibrosis. Common locations for DIE include the uterosacral ligaments, anterior rectosigmoid colon, bladder, rectovaginal septum, round ligaments, and muscular wall of pelvic organs. It can also be found in scar tissue, and has been reported in C-section scars within the uterine wall or anterior abdominal wall (Figure 4).11 Uterosacral Ligaments: “Uterosacral ligaments are the most common location for DIE (Figure 5). With disease involvement, the ligaments can become thickened and develop adhesions to surrounding structures. MRI is noted to have a 69% sensitivity and >90% specificity for diagnosing uterosacral ligament deep infiltrating endometriosis, and is better than endorectal and endovaginal ultrasound.9”Intestinal: “DIE can deeply invade into the muscularis propria of the rectosigmoid colon and this deep invasion typically requires surgical resection. At MRI, this has been described as a “mushroom cap” sign where the low intensity of the mushroom base is attributed to hypertrophy and fibrosis of the muscularis propria and the high signal intensity of the mushroom cap is attributed to the intact, overlying mucosa and submucosa which are displaced into the bowel lumen (Figure 6) .9”Bladder: “Bladder involvement with DIE usually involves the posterior wall and can result in partial or complete obliteration of the vesicouterine pouch. Similar to DIE in other locations, bladder involvement with DIE can appear as T2W hypointense infiltrative or nodular lesions centered in the vesicouterine pouch. There can be variable foci of T1W and T2W signal intensity within these DIE lesions, which represent the trapped endometrial glands (Figure 7).” Round Ligament: “The round ligament is another site which can be involved with DIE, with one study of women undergoing laparoscopy for DIE showing involvement of the round ligament in 15% of cases.9”

This study differentiates between findings on the MRI and disease present at surgery. Follow the link to see more information as well as several pictures. 

  • Thalluri, A. L., Knox, S., & Nguyen, T. (2017). MRI findings in deep infiltrating endometriosis: A pictorial essay. Journal of Medical Imaging and Radiation Oncology61(6), 767-773. https://doi.org/10.1111/1754-9485.12680 

“In conclusion, endometriosis is an important gynaecological disorder which can impact significantly an individual’s quality of life and has major implications on fertility. Pre‐operative MRI has high specificity for the diagnosis and characterization of disease extent, and may guide surgical management, which remains the mainstay of curative treatment.” Posterior cul de sac: “The posterior cul‐de‐sac (recto‐uterine pouch) represents the lowest portion of the abdomino‐pelvic cavity in the supine position.34 Disease here is responsible for the majority of symptomatic cases of endometriosis3 and may significantly hinder laparoscopic assessment and treatment due to poor access and visualization as result of compartment obliteration.5 On MRI, posterior cul‐de‐sac disease is characterized by endometrial plaques which display T1 hyperintensity and variable T2 signal, dependent on the composition of haemorrhage, glandular content and fibrosis….Adhesions may appear as subtle low signal strands between organs and bowel loops. MRI accuracy has been reported as 71.9% in demonstrating features of posterior cul‐de‐sac obliteration and 61.4% for highlighting adhesions in the posterior cul‐de‐sac.Intestinal: “Intestinal endometriosis occurs in 12–37% of endometriosis patients1 with the rectosigmoid colon the most commonly affected region.2 Clinical features vary from mild to severe and include cyclical abdominal pain, constipation/diarrhoea, dyschezia and haematochezia.6 Implants are usually serosal and have the potential to erode through the sub‐serosal layers (although will rarely involve the mucosa), with resultant thickening and fibrosis of the muscularis propria.2 Cyclical haemorrhage and intermittent leakage of endometriotic contents result in a chronic inflammatory reaction leading to the formation of adhesions and bowel strictures. A pre‐operative diagnosis of bowel involvement may highlight the need for colorectal input should bowel resection be required.2 On MRI, bowel adhesions are visualized similar to posterior cul‐de‐sac adhesions; there may be clustering or tethering of bowel loops with direct bands, poor interface visualization and loss of pericolic or peri‐mesenteric fat planes (Fig. 2a).5Endometriomas: “Endometriomas represent thick‐walled cysts, containing degenerated blood products. They can involve a variety of pelvic locations with the majority occurring within the ovaries. MRI is the best imaging modality for identifying endometriomas, with a specificity of 98%.Anteflexion and Retroflexion of the uterus: “Anteflexion of the uterus may occur when there is endometriosis and adhesion formation in the anterior compartment between the bladder peritoneal reflection and the anterior uterine serosa….Retroflexion of the uterus occurs when there is endometriotic involvement of the posterior compartment, in particular the uterosacral ligaments.7 The torus uterinus is a small transverse thickening that binds the original insertion of the uterosacral ligaments to the posterior cervix. On MRI, the torus uterinus is usually unable to be viewed unless there is pathological thickening present, such as in endometriotic involvement.11 This causes fibrosis of the ligaments, tethering the uterus posteriorly and resulting in uterine retroflexion (Fig. 4). When retroflexion of the uterus has occurred, there is often irregular configuration or shortening of the posterior surface of the uterus, which is indicative of tethering.”Thickened uterosacral ligament: “The uterosacral ligament attaches the cervix to the sacrum and holds the uterus in position. The uterosacral ligament, in addition to the posterior cul‐de‐sac, is the most common pelvic sites of involvement in deep pelvic endometriosis, with specificity for the diagnosis of uterosacral ligament endometriosis greater than 90% on MRI.7 The proximal, medial uterosacral ligament portion is the most commonly affected part by endometriosis.” Haematosalpinx: “Endometriotic involvement of the fallopian tubes usually occurs within the sub‐serosal layer and is strongly associated with infertility due to resultant peritubal adhesions and subsequent tubal obstruction.7 On MRI, the presence of T1 hyperintense blood products within a dilated tube (haematosalpinx) is highly specific for endometriosis, and may be the only feature of disease on MRI.”Elevated vaginal fornices: “Vaginal forniceal elevation may occur in endometriosis as a result of regional adhesions (Fig. 7). There are several MRI features of forniceal elevation including the upper level of the fornix being superior to the angle of the uterine isthmus, acute angulation of the fornix, or the fornix being visibly pulled in a superior direction with subsequent stretching of the vaginal wall.7 Thickening of the superior one‐third of posterior vaginal wall with or without nodularity may also be visualized.7 Nodules are identified as low signal intensity foci on T2WI.1 T1WI (particularly fat saturated images) may show high signal intensity indicative of active/subacute haemorrhagic deposits.”