Your patient is a healthy 25 year-old female presenting for evaluation of abdominal pain. Her pain started approximately 3 hours prior to presentation and since onset has only increased. She has associated nausea and vomiting but denies diarrhea/flatus. She is very slender but well-nourished in appearance, her abdomen is diffusely tender, most impressively in the right lower quadrant, and mildly distended. She has a normal cervix, no cervical motion tenderness, and an empty rectal vault. She denies trauma, surgical history, or history of inflammatory bowel disease. Your main clinical concerns are appendicitis and bowel obstruction. Do you need oral contrast to appropriately diagnose this patient?
Oral contrast has been a key ingredient in the diagnosis of nontraumatic abdominal pain for decades. But do we really need it at all? And in what circumstances? And at what consequence?
Oral contrast increases radiation exposure by 11%, increases risk of emesis and subsequent placement of NG tubes, and in some cases, incidence of hospital-acquired pneumonia and ARDs. It also increases our emergency department lengths of stay for patients requiring abdominal CT, by as much as 2 hours.
And for these costs, it's not particularly clear that oral contrast even gets to the area of interest or helps in diagnostic certainty. In the case of appendicitis, oral contrast only gets to the appendix 72% of the time. Although oral contrast is helpful in identifying appendicitis in non-inflamed appendices, CTs with and without oral contrast perform similarly in the diagnosis of acute appendicitis. This remains true even in the very slender patients with decreased intra-abdominal fat and BMI < 25.
When considering nontraumatic abdominal pain in general, the addition of oral contrast does very little to help in diagnosis. Multiple retrospective studies of departments which have adopted a "limited oral contrast" approach have demonstrated that oral contrast can decrease length of stay and patient risk without causing any decrease in diagnosis accuracy.
However, oral contrast is extremely helpful in the following circumstances: the identification of abscess, fistulization, and anastomotic leak or perforation. For patients with high risks of these above complications, for example, those with inflammatory bowel disease, recent surgery, or immunocompromise increasing their likelihood of abscess formation, oral contrast is likely to be helpful in appropriate and safe diagnosis.
I suggest the following very simple guideline to help you determine if your next patient needs oral contrast:
The literature supports the use of oral contrast for abdominal/pelvis CT scans in emergency department patients in the following circumstances:
1: post-surgical patients
2: patients with inflammatory bowel disease.
It is not necessary to administer oral contrast in patients without the above indications unless warranted by clinical judgment.
If you are interested in reading more about oral contrast utilization in emergency department evaluation of nontraumatic abdominal pain, please see the below annotated bibliography for more information.