How to improve MRI accuracy in detecting deep infiltrating colorectal endometriosis: MRI findings vs. laparoscopy and histopathology.

To verify whether the capability of magnetic resonance imaging (MRI) in diagnosing deep infiltrating colorectal endometriosis (DICE) is improved using an association of MRI findings. The imaging database of our Institute of Radiology was retrospectively reviewed to identify patients subjected to MRI for a suspicion of deep infiltrating endometriosis. Medical history was then investigated and only patients who were also subjected to laparoscopy (LA) were included. Absence of LA represented the exclusion criterion. Images were evaluated twice by two radiologists using two different diagnostic criteria for an abnormal result: the contemporary presence of nodules or hypointense plaque-like lesions in the adjacent fat plane and bowel wall thickness, without (first criterion) or with (second criterion) semicircular shape (i.e. "radial and retracting shape"). Radiologists worked in consensus evaluating images in two separate sessions, using the first criterion in the first section and the second criterion in the second one. MRI results were compared with LA or histopathology as the gold standard by 2 × 2 tables and statistically analyzed (k statistics). Likelihood-ratio test was also performed, being independent from the prevalence of the disease. By consulting case sheets, 33/50 females (ranging age 24-39 years, mean age 32.2 years) who were subjected to MRI also underwent LA. Intestinal resection for DICE was performed in 11/33 patients; in 22/33 superficial intestinal foci, adhesions/nodules in the fat plane were simply removed. When the first criterion was applied, MRI agreement with histopathology or LA was poor (51.5 %) (k value = 0.20; p < 0.055), while it was improved (96.9 %) when using the second diagnostic criterion (k value = 0.93; p < 0.0000). Likelihood ratio was 1.375 (95 % CI 0.69-2.72) using the first and 22 (95 % CI 20.08-24.1) using the second criterion. The second criterion, or the joint presence of nodules or hypointense plaque-like lesions in the adjacent fat plane and bowel wall thickness showing "radial and retracting shape", improves MRI capability in DICE diagnosis. It can be considered an effective indicator of DICE on T2-weighted images at 1.5-T MRI, and can ensure the correct preoperative assessment of the disease for the best therapeutic procedure and treatment planning.