There is a clear consensus that noncontrast CT holds poorer performance compared against a CT with IV contrast. Standard CT abdomen and pelvis with IV contrast can provide evidence of inflammation of an affected gastrointestinal segment. Although there may be less than optimal bowel distention with positive luminal contrast (compared with volume loading techniques) and positive contrast may obscure subtle stratified mural enhancement and more subtle areas of active inflammation, CT with positive luminal contrast can identify wall thickening, luminal narrowing, and adjacent inflammatory changes that may be seen in CD [39]. In addition to assessing for inflammation, standard CT with IV contrast can also evaluate for CD complications, including bowel obstruction, fistula formation, and abscess formation, and positive luminal contrast is preferable to no oral contrast in this scenario. Sensitivities for CT-based evaluation for stenosis/obstruction range from 85% to 94% with very high specificities [40,41]. Sensitivities for abscesses are also very good, ranging from 86% to 100% [27,36]. There is more variable performance for fistula detection with sensitivities ranging from 68% to 100% [27,40,42]. One study showed a very low sensitivity of 20% for enteroenteric fistulas in their series [40]. Thus, in the acute setting, standard CT with IV contrast is a suitable option for assessment. On the other hand, if the patient is relatively well and able to tolerate the oral contrast requirements of CT enterography, the optimized bowel protocol increases sensitivity for more subtle inflammation. CT Enteroclysis CT enteroclysis is a CT-based examination in which a nasoduodenal tube is placed to allow controlled distention of the small bowel. Typically, neutral contrast is continuously infused into the small bowel during CT, and IV contrast is also given. This procedure typically allows for better distention of the small bowel compared with oral ingestion at CT enterography [43,44].
Crohn Disease. There is a clear consensus that noncontrast CT holds poorer performance compared against a CT with IV contrast. Standard CT abdomen and pelvis with IV contrast can provide evidence of inflammation of an affected gastrointestinal segment. Although there may be less than optimal bowel distention with positive luminal contrast (compared with volume loading techniques) and positive contrast may obscure subtle stratified mural enhancement and more subtle areas of active inflammation, CT with positive luminal contrast can identify wall thickening, luminal narrowing, and adjacent inflammatory changes that may be seen in CD [39]. In addition to assessing for inflammation, standard CT with IV contrast can also evaluate for CD complications, including bowel obstruction, fistula formation, and abscess formation, and positive luminal contrast is preferable to no oral contrast in this scenario. Sensitivities for CT-based evaluation for stenosis/obstruction range from 85% to 94% with very high specificities [40,41]. Sensitivities for abscesses are also very good, ranging from 86% to 100% [27,36]. There is more variable performance for fistula detection with sensitivities ranging from 68% to 100% [27,40,42]. One study showed a very low sensitivity of 20% for enteroenteric fistulas in their series [40]. Thus, in the acute setting, standard CT with IV contrast is a suitable option for assessment. On the other hand, if the patient is relatively well and able to tolerate the oral contrast requirements of CT enterography, the optimized bowel protocol increases sensitivity for more subtle inflammation. CT Enteroclysis CT enteroclysis is a CT-based examination in which a nasoduodenal tube is placed to allow controlled distention of the small bowel. Typically, neutral contrast is continuously infused into the small bowel during CT, and IV contrast is also given. This procedure typically allows for better distention of the small bowel compared with oral ingestion at CT enterography [43,44].