In the past, we have always used PO and IV contrast for CT abdomen/pelvis scans in studies to "rule out" SBOs, but recently we have been told by the Chief of Surgery Dr. Nicastro that PO contrast is not necessary to rule out SBOs however some surgical residents and attendings may still ask for PO contrast. Here are some learning points so that you can advocate for your patient and discuss with the surgical team about why we may not need PO contrast in your next SBO patient!
Historical Use of PO Contrast in SBO Evaluation
Early CT protocols included PO and IV contrast for abdominal imaging to better outline the bowel lumen and identify transition points.
PO contrast was initially thought to improve diagnostic accuracy by helping to distinguish dilated bowel from collapsed bowel and aiding in localizing the obstruction. (Balthazar 1997)
Advancements in CT Technology
Multidetector CT scanners introduced in the 2000s drastically improved resolution, allowing clear visualization of bowel loops, wall enhancement, and obstruction points without the need for PO contrast.
IV contrast became the primary agent for assessing bowel wall integrity, ischemia, and complications, which are critical components in SBO management. (Jaffe 2006; Taylor 2013)
Evidence showed high diagnostic accuracy (90–95%) with IV contrast alone, questioning the need for PO agents in most cases. (Gore 2000; American College of Radiology 2020)
Other Contraindications for PO Contrast Use
PO contrast often delays imaging as patients may need 1–2 hours to ingest the contrast and allow it to move through their digestive tract, delaying care.
Patients with high-grade SBO may be unable to tolerate oral intake, increasing the risk of vomiting and aspiration. (Maglinte 2013)
Excessive intraluminal contrast can also obscure bowel wall features, including mural enhancement or signs of ischemia. (Paulson 2005)
However, even though PO contrast may not be useful in suspected high-grade SBOs, it still has its uses if other diagnoses are suspected:
Indications for PO Contrast in CT abdomen/pelvis
PO contrast can help delineate the transition point in indeterminate, low-grade, or partial obstructions.
Water-soluble oral contrast (e.g., Gastrografin) may help identify extraluminal leak sites after bowel surgery.
PO contrast can help visualize and evaluate known or suspected enteric fistulas between bowel segments or between bowel and other structures (e.g., bladder, skin).
Oral contrast can help assess strictures, skip lesions, or fistulas—especially in combination with enterography techniques to evaluate inflammatory bowel disease (IBD).
CT Enterography or CT Enteroclysis requires neutral or low-density PO contrast to assess small bowel mucosa and pathology (e.g., Crohn’s disease, obscure GI bleeding).
PO contrast may help clarify mass relationships to bowel loops or identify lumen involvement in preoperative planning for known mass lesions.
Takeaways
IV contrast-enhanced CT is now the standard for initial SBO evaluation, with PO contrast reserved for select, stable cases of suspected partial obstruction.
There may still be an indication for PO contrast based on the patient’s clinical stability, level of obstruction, and specific diagnostic question.
References:
Balthazar EJ, et al. “CT of SBO: value in establishing diagnosis and determining degree and cause.” AJR Am J Roentgenol. 1994, 1997.
Gore RM, et al. “Bowel obstruction.” Radiol Clin North Am. 2000.
Jaffe TA, et al. “CT of small-bowel obstruction: how reliable is diagnosis and extent?” AJR Am J Roentgenol. 2006.
Maglinte DDT, et al. “Radiologic diagnosis of small-bowel obstruction: current role and future trends.” Radiol Clin North Am. 2013.
Paulson EK, et al. “Small-bowel obstruction: the role of CT evaluation and contrast agents.” Radiology. 2005.
Taylor GA, et al. “ACR Appropriateness Criteria® on suspected small-bowel obstruction.” J Am Coll Radiol. 2013.
American College of Radiology. “ACR Appropriateness Criteria® Suspected Small-Bowel Obstruction.” 2020.