A systematic review in the American Journal of Surgery compared various combinations of oral, rectal and IV contrast for CT scanning to evaluate patients for appendicitis. All protocols performed well including imaging without oral, rectal or IV contrast. The authors believe a prospective comparative trial is needed.
A related commentary in Internal Medicine News mentions some caveats, suggesting that increased experience in interpretation may be necessary for non contrast exams, that non contrast imaging is particularly challenging in lean individuals and that non contrast exams sacrifice some ability to detect other pathology that may cause pain.
This information could prove useful for those patients with possible appendicitis in whom contrast administration is contraindicated.