Oral contrast for CT abdominal imaging
Author: Laurel Barr, MD (EM Attending Physician, Memorial Hospital Marysville Ohio)
Edited by: Alex Koyfman, MD (@EMHighAK) and Brit Long, MD (@long_brit, EM Chief Resident at SAUSHEC, USAF)
You begin your night shift with a 9 year old previously healthy male complaining of abdominal pain. His pain began several hours ago periumbilically and has since moved to the right lower quadrant. Mom reports a fever of 100.4F and gave Tylenol prior to arrival. He has vomited once and has no diarrhea. Vital signs include Temp 99.0F, HR 102, RR 16, BP 112/68. He appears somewhat dehydrated. His right lower quadrant is tender to palpation with voluntary guarding, but negative Psoas and Rovsing’s sign. He will not jump due to pain. Labs show leukocytosis of 12. You decide to order a CT scan to evaluate for acute appendicitis but before you do, a trauma alert is called.
Your next patient is a 28 year old female involved in a high-speed MVC complaining of abdominal pain. Vitals include HR 112, RR 20, BP 126/82, and Temp 98.6F. There is a seatbelt sign across the lower abdomen as well as diffuse tenderness to palpation with involuntary guarding. As you put in orders on your patients, you wonder if either of these patients would benefit from oral contrast.
After graduating from residency, I began working in a small community ED. My first few months, the nurses would frequently ask me if I wanted oral contrast when I ordered abdominal CT scans. I found this an odd question, since in residency I rarely thought about oral contrast. In fact, after our hospital switched to electronic ordering I only thought of it the few times the surgery residents would call to ask me if I knew how to order it. There was actually no way to order oral contrast in the new ordering system. No one seemed to miss it. It seemed like it was routine at my new hospital.
Abdominal CT with oral contrast has traditionally been used to assist in visualization of the bowel. It was thought to be helpful in the case of small bowel injury in blunt abdominal trauma, appendicitis, and diverticulitis. However, with the advent of 64 multidetector CT scans, image quality may be increasing enough that oral contrast is no longer necessary to aid in diagnosis.
So should you order oral contrast for either of these patients? The short answer is no, but maybe.
The exclusion of oral contrast has been heavily studied in blunt abdominal trauma. Abdominal CT with IV contrast reaches 95% sensitivity and 99% specificity without oral contrast. Several retrospective and prospective studies show few abdominal injuries missed on CT imaging requiring surgical repair would have been detected by the use of oral contrast.,, A randomized controlled trial confirmed that oral contrast was not helpful in identifying bowel injury diagnosed on laparotomy. A meta-analysis also concluded no difference between abdominal CTs with and without oral contrast. Studies conducted on pediatric patients demonstrated similar results.,
The addition of IV contrast to abdominal CT is helpful in the diagnosis of acute appendicitis, with a sensitivity that approaches 100%. Several randomized controlled trials do not show an advantage to adding oral contrast. , An additional study found no cases of missed appendicitis or need for repeat CT at 30 days when abdominal CTs were performed without oral contrast. There are a few trials examining the need for oral or rectal contrast in pediatrics, partially because most trials compare CT to US or MRI for diagnosis in order to reduce radiation exposure. The usefulness of oral contrast in pediatrics may be dependent on age and weight.
Undifferentiated Abdominal Pain
In patients presenting to the ED with undifferentiated abdominal pain, oral contrast also does not contribute to diagnosis or disposition. A prospective trial was conducted in which patients received abdominal imaging without IV contrast before and after oral contrast. In this study, variations in diagnosis were determined to be due to radiologist interobserver agreement and not due to oral contrast. Oral contrast is no longer routinely used at academic centers.
Disadvantages of oral contrast administration include increased radiation exposure, possible aspiration pneumonitis, increased time to diagnosis and ED length of stay, or need for NG tube placement.,, It can potentially delay time to OR by over an hour and time to discharge by 2 hours. A protocol eliminating oral contrast from routine CT scans can decrease ED LOS by 97 minutes.
Oral contrast should no longer routinely be used in abdominal CT in the Emergency Department. It has the potential for adverse effects and has been shown to delay disposition time and increase ED length of stay without improving patient outcomes. It may be helpful in specific incidences to optimize images if requested by surgery or radiology.
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