E1818. MRI for Endometriosis: The Impact of Under and Overcalling Disease
  1. Sneha Shukla; Mayo Clinic
  2. Tatnai Burnett; Mayo Clinic
  3. Wendaline VanBuren; Mayo Clinic
Endometriosis refers to the presence of endometrial glandular and stromal tissue outside of the uterus. This tissue can be found throughout the abdomen and pelvis, including endometriomas, peritoneal deposits and deep infiltrating disease. Depending on size and location these hormone sensitive deposits can cause cyclical inflammation and fibrosis, which can lead to infertility and debilitating pain. MRI is a useful tool for endometriosis diagnosis and staging and can impact surgical planning. However, there is a learning curve for disease identification and reporting of subtle disease, which may lead to radiologists both under and overcalling disease.

Educational Goals / Teaching Points
Recognize the MRI findings of endometriosis, including deep infiltrative endometriosis. Learn the pertinent positives and negatives to mention in the radiology report. Understand the consequences of under and overcalling on medical and surgical management.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
MRI is useful in imaging for endometriosis due to its excellent soft tissue differentiation. The main MRI sequences used are T2 weighted images in three orthogonal planes, T1 weighted images with and without fat saturation, and gadolinium enhanced sequences. Ovarian endometriomas are classically characterized by their intrinsic T1 hyperintensity, T2 hypointensity (or T2 shading) and minimal enhancement. Serosal deposits and deep infiltrating disease have variable imaging characteristics, but are most commonly seen as T2 hypointense nodular or spiculated thickening which can cause architectural distortion and mucosal thickening of the involved structures. Given the variable appearance of serosal and deep infiltrative disease, certain findings may be overcalled leading to surgical intervention. For example, abnormal thickening of the uterosacral ligament from scar tissue post hysterectomy can be mistaken for an implant. The anterior and posterior cul-de-sacs are common locations of deep infiltrating disease, however can be difficult to evaluate. Superimposed vessels can appear as soft tissue thickening and nodularity. Phleboliths, which appear as T1 hyperintense pelvic foci, can also be mistaken for endometriotic deposits. Findings can also be overlooked, leading to a delay in diagnosis. For example, endometriomas can be mistaken for hemorrhagic ovarian cysts or adnexal masses. Adjacent bowel wall thickening can be attributed to further evidence of malignancy.

Detection of endometriosis on MRI can be difficult, and the reporting of specific nuances can impact surgical and medical management. Especially for those who see few cases throughout the year, the learning curve can be steep. Through understanding the challenges and limitations of MRI for endometriosis, we can identify areas of practice improvement and enhance communication of subtle findings with our surgical colleagues.