Can MR enterography screen for perianal disease in pediatric inflammatory bowel disease?

BACKGROUND: Pediatric Crohn's disease is associated with perianal disease (PAD). Magnetic resonance enterography (MRE) assesses small bowel involvement in pediatric inflammatory bowel disease (PIBD). Pelvic MRI (P-MRI) is the gold standard for assessing PAD. PURPOSE: To determine if MRE can accurately detect PAD in PIBD, distinguishing perianal fistulae (PAF) from perianal abscesses (PAA), referenced against P-MRI. STUDY TYPE: Retrospective. POPULATION: Seventy-seven PIBD patients, 27 females (mean age 14.1 years), with P-MRI and MRE within 6 months. FIELD STRENGTH/SEQUENCE: 1.5T and 3T; P-MRI: sagittal fat suppressed (FS) T2 fast spin-echo (FSE), coronal short tau inversion recovery, axial T1 FSE, coronal and axial postcontrast FS T1 FSE; MRE: coronal balanced steady-state free-precession (SSFP), coronal cine SSFP, coronal and axial single-shot T2 FS, axial SSFP, coronal ultrafast 3D T1 -weighted gradient echo FS (3D T1 GE), axial diffusion-weighted imaging, coronal and axial postcontrast 3D T1 GE FS. ASSESSMENT: Two radiologists independently, then by consensus, assessed randomized MRI exams, recording PAF number, location, and length; and PAA number, location, length, and volume. Sensitivity analysis used clinical disease as the gold standard, calculated separately for P-MRI and MRE. STATISTICAL TESTS: Comparing MRE and P-MRI consensus data, sensitivity, specificity, positive, and negative predictive values (P/NPV) were calculated. Inter- and intrareader reliability were assessed using kappa statistics. RESULTS: P-MRI and MRE were paired, detecting PAD in 73 patients, PAF in 63, and PAA in 31 P-MRI. MRE sensitivities, specificities, PPV, and NPV were: PAD 82%, 100%, 100%, 23%; PAF 74%, 71%, 92%, 38%; PAA 51%, 85%, 69%, 72%; clinical 82%, 22%, 37%, 69%; clinical P-MRI 96%, 8%, 37%, 80%. MRE interreader agreement for PAD was moderate (kappa = 0.51 [0.29-0.73]), fair for PAF and PAA. DATA CONCLUSION: Using a standard technique, MRE can detect PAD with high specificity and moderate sensitivity in PIBD, missing some PAF and small PAA. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1638-1645.