Grand Rounds

Is Ultrasound or MRI Best When Assessing Colorectal Endometriosis?

BACKGROUND AND PURPOSE:

Intestinal involvement may be seen in 5% to 12% of patients with endometriosis
Patients may present with serious GI symptoms and signs (e.g., cyclical rectal bleeding)
Transvaginal sonography is the first line imaging technique to detect intestinal endometriosis
MRI and rectal endoscopic sonography (RES) are used as second line imaging modalities and also can determine depth of invasion
Kim et al. (JMIG, 2017) compared accuracies of magnetic resonance imaging (MRI) and rectal endoscopic sonography (RES) in the prediction of the infiltration depth of colorectal endometriosis

Retrospective cohort study
Inclusion: Patients with symptomatic deep infiltrating endometriosis of the rectum who had colorectal resection
All patients underwent abdominopelvic MRI and RES
Performance characteristics and intermethod agreement were calculated

40 patients were included in this study with a median age of 33 years
MRI detection of muscularis layer invasion: PPV (100%)
MRI detection of submucosal/mucosal layer involvement: Sensitivity (47%), specificity (81%), PPV(69%), NPV (63%)
RES detection of muscularis infiltration: PPV (93%)
RES detection of submucosal/mucosal layer involvement: Sensitivity (79%), specificity (48%), PPV (58%), NPV (71%)

Compared to RES, MRI is valuable in detecting rectal endometriosis but less accurate in detecting submucosal/mucosal involvement
MRI PPV is higher for both muscularis and submucosal/mucosal infiltration
However, RES has a better NPV for the detection of submucosal/mucosal infiltration
When bowel involvement is detected by MRI, RES is not needed to confirm this finding
If bowel infiltration is not detected by MRI, RES is necessary to rule out this finding (especially if a patient is symptomatic)

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