Normal enhancement of the small bowel: Evaluation with spiral CT

Purpose: The purpose of this work was to determine normal contrast enhancem ent of the small bowel with biphasic spiral CT, using water as oral contras t agent. Method: Biphasic spiral CT was performed in 50 healthy patients undergoing evaluation as potential renal donors. All patients received 500 ml of water as oral contrast agent and 150 ml of Omnipaque 350 administered by mechani cal injector at a rate of 3 ml/s. Dual phase CT of the abdomen was performe d in each patient. Acquisition of early phase images began 30 s after the s tart of the intravenous injection, and portal phase images were obtained 60 s after initiation of the contrast agent injection. Attenuation measuremen ts (in Hounsfield units) were obtained from the wall of the small bowel (du odenum, jejunum, ileum) in both the arterial and the portal phases. Results: During the arterial phase, the mean (95% confidence interval) atte nuation of the duodenum, jejunum, and ileum was 120 (+/- 5), 119 (+/- 5), a nd 118 (+/- 5) HU, respectively. During the portal phase, the average atten uation of the duodenum, jejunum, and ileum was 111 (+/- 4), 111 (+/- 3), an d 107 (+/- 3) HU, respectively. There was no statistically significant diff erence between the attenuation of the duodenum, jejunum, or ileum within ei ther the arterial or the portal venous phases. There was a statistically si gnificant difference in small bowel enhancement between the arterial and po rtal venous phases. Conclusion: There is no important variation in small bowel attenuation duri ng the 30 and 60 s scanning phases. This study serves as a normal reference that may be helpful when spiral CT is used to evaluate ischemic bowel or i nflammatory small bowel diseases.