MRI Abdomen and Pelvis Standard MRI with a routine protocol (ie, without and with IV contrast and without oral contrast enterography technique) can detect evidence of CD if the patient cannot tolerate large volumes of oral contrast. However, the lack of bowel optimization decreases evaluation of inflammation. Thus, the key question of quiescent disease versus low levels of continuing inflammation central to this variant is not answered to the same confidence as with MR enterography (with optimized bowel technique). One study (n = 100) reported a sensitivity of 50% to 86% and specificity of 93% to 94% for wall thickening [73]. The literature on mucosal healing and MR has centered on MR enterography as opposed to standard MR without enterography protocol. MR enterography has been shown to correlate with response to therapy and mucosal healing [111,112]. One prospective multicenter study (n = 48) showed 90% accuracy of ulcer healing determination at MR enterography, utilizing ileocolonoscopy as the reference standard [113]. In this specific clinical scenario, the patient is typically able to tolerate enterography technique, and consequently, bowel optimization should be undertaken as opposed to standard MRI for this situation. For CD complications, the diagnostic ability of MRI is similar to its CT counterpart with similar reported sensitivities and specificities in various series [27,40,58,72]. The sensitivity for stenosis/obstruction ranges from 87% to 92% with high specificities; detection performance remains high for abscesses, with sensitivity ranging from 86% to 100%. As with CT, the detection for fistulas is more variable, ranging from 40% to 100%. Because of the superior soft-tissue contrast, perianal disease including fistulation to the perineum is best evaluated at MRI, using a small field-of-view, focused examination [74-76]. Standard MRI without IV contrast has been investigated because of emerging concerns with IV gadolinium use and potential long-term accumulation in the body and brain.
Crohn Disease. MRI Abdomen and Pelvis Standard MRI with a routine protocol (ie, without and with IV contrast and without oral contrast enterography technique) can detect evidence of CD if the patient cannot tolerate large volumes of oral contrast. However, the lack of bowel optimization decreases evaluation of inflammation. Thus, the key question of quiescent disease versus low levels of continuing inflammation central to this variant is not answered to the same confidence as with MR enterography (with optimized bowel technique). One study (n = 100) reported a sensitivity of 50% to 86% and specificity of 93% to 94% for wall thickening [73]. The literature on mucosal healing and MR has centered on MR enterography as opposed to standard MR without enterography protocol. MR enterography has been shown to correlate with response to therapy and mucosal healing [111,112]. One prospective multicenter study (n = 48) showed 90% accuracy of ulcer healing determination at MR enterography, utilizing ileocolonoscopy as the reference standard [113]. In this specific clinical scenario, the patient is typically able to tolerate enterography technique, and consequently, bowel optimization should be undertaken as opposed to standard MRI for this situation. For CD complications, the diagnostic ability of MRI is similar to its CT counterpart with similar reported sensitivities and specificities in various series [27,40,58,72]. The sensitivity for stenosis/obstruction ranges from 87% to 92% with high specificities; detection performance remains high for abscesses, with sensitivity ranging from 86% to 100%. As with CT, the detection for fistulas is more variable, ranging from 40% to 100%. Because of the superior soft-tissue contrast, perianal disease including fistulation to the perineum is best evaluated at MRI, using a small field-of-view, focused examination [74-76]. Standard MRI without IV contrast has been investigated because of emerging concerns with IV gadolinium use and potential long-term accumulation in the body and brain.