Crohn Disease the superior soft-tissue contrast, perianal disease including fistulation to the perineum is best evaluated at MRI, using a small field of view and 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. Noncontrast techniques, such as diffusion-weighted imaging (DWI), have been used to evaluate evidence for CD. There is growing literature examining its promise in detecting active disease versus quiescent disease for complication evaluation and disease monitoring, although many of the studies involve DWI in the context of enterography technique [77]. One study without enterography technique [48] reported a sensitivity of 49% to 82% and specificity of 85% to 93% for DWI, although lower specificities have been reported at meta-analysis [78]. Overall, DWI appears to have moderate sensitivity but low specificity leading to increased false positives for disease activity [77]. Thus, the current consensus is that noncontrast only techniques such as DWI can be done but there is likely improved performance with the information gained from post-IV contrast series. Severely ill patients are less likely to be able to hold still for the duration of an MRI examination, leading to increased artifact and poorer image quality. In these instances, other options may be preferable, particularly CT enterography or standard abdomen and pelvic CT. Radiography Abdomen Radiographs of the abdomen are limited in the initial diagnosis for CD. The ability to directly visualize bowel pathology is limited, and evidence for CD is instead inferred indirectly. Radiographs may be useful in severely ill presenting patients to evaluate for the presence of bowel perforation or obstruction.
Crohn Disease. Crohn Disease the superior soft-tissue contrast, perianal disease including fistulation to the perineum is best evaluated at MRI, using a small field of view and 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. Noncontrast techniques, such as diffusion-weighted imaging (DWI), have been used to evaluate evidence for CD. There is growing literature examining its promise in detecting active disease versus quiescent disease for complication evaluation and disease monitoring, although many of the studies involve DWI in the context of enterography technique [77]. One study without enterography technique [48] reported a sensitivity of 49% to 82% and specificity of 85% to 93% for DWI, although lower specificities have been reported at meta-analysis [78]. Overall, DWI appears to have moderate sensitivity but low specificity leading to increased false positives for disease activity [77]. Thus, the current consensus is that noncontrast only techniques such as DWI can be done but there is likely improved performance with the information gained from post-IV contrast series. Severely ill patients are less likely to be able to hold still for the duration of an MRI examination, leading to increased artifact and poorer image quality. In these instances, other options may be preferable, particularly CT enterography or standard abdomen and pelvic CT. Radiography Abdomen Radiographs of the abdomen are limited in the initial diagnosis for CD. The ability to directly visualize bowel pathology is limited, and evidence for CD is instead inferred indirectly. Radiographs may be useful in severely ill presenting patients to evaluate for the presence of bowel perforation or obstruction.