For more indolent presentations in which the patient is able to tolerate large volumes of oral contrast, CT enterography is preferred because it is can detect more subtle findings of CD compared with a standard CT with positive oral contrast. In contrast, in the acute presentation in which the patient is severely ill and unable to tolerate the large volume requirements, a standard CT (without or with oral contrast) may be the preferred choice. Presumably, any findings of CD would not be subtle in this situation. Crohn Disease CT Abdomen and Pelvis Standard abdomen and pelvis CT with IV contrast with a routine protocol (ie, without neutral oral contrast enterography technique) can be useful in the initial presentation of a patient with CD without a known prior diagnosis, particularly in the instance of an acutely ill individual who may be unable to tolerate large amounts of oral contrast for an enterography protocol. Standard CT also allows for alternative diagnoses that may mimic CD such as appendicitis in this variant. This adds to the potential utility of this modality for this variant. However, if the patient is able to tolerate the oral contrast requirements of CT enterography, optimizing bowel technique improves examination performance over standard CT and should be preferred. Although standard abdomen and pelvis CT can be done either with or without the administration of IV contrast, it is evident that many of the processes, such as mural enhancement associated with CD require IV contrast for optimal assessment. Without IV contrast, such processes can only be inferred by associated findings, such as wall thickening, which may not occur in mild inflammation. In fact, the importance of contrast can be underscored by the emphasis on determining the optimal timing of imaging following IV contrast administration as opposed to comparisons between IV contrast and noncontrast CT [22]. A prior meta-analysis that evaluated CT performance included studies that were all conducted with IV contrast [25].
Crohn Disease. For more indolent presentations in which the patient is able to tolerate large volumes of oral contrast, CT enterography is preferred because it is can detect more subtle findings of CD compared with a standard CT with positive oral contrast. In contrast, in the acute presentation in which the patient is severely ill and unable to tolerate the large volume requirements, a standard CT (without or with oral contrast) may be the preferred choice. Presumably, any findings of CD would not be subtle in this situation. Crohn Disease CT Abdomen and Pelvis Standard abdomen and pelvis CT with IV contrast with a routine protocol (ie, without neutral oral contrast enterography technique) can be useful in the initial presentation of a patient with CD without a known prior diagnosis, particularly in the instance of an acutely ill individual who may be unable to tolerate large amounts of oral contrast for an enterography protocol. Standard CT also allows for alternative diagnoses that may mimic CD such as appendicitis in this variant. This adds to the potential utility of this modality for this variant. However, if the patient is able to tolerate the oral contrast requirements of CT enterography, optimizing bowel technique improves examination performance over standard CT and should be preferred. Although standard abdomen and pelvis CT can be done either with or without the administration of IV contrast, it is evident that many of the processes, such as mural enhancement associated with CD require IV contrast for optimal assessment. Without IV contrast, such processes can only be inferred by associated findings, such as wall thickening, which may not occur in mild inflammation. In fact, the importance of contrast can be underscored by the emphasis on determining the optimal timing of imaging following IV contrast administration as opposed to comparisons between IV contrast and noncontrast CT [22]. A prior meta-analysis that evaluated CT performance included studies that were all conducted with IV contrast [25].