What is the recommended protocol for a CT abdomen with intravenous (IV) and oral contrast?

From the Guidelines

The recommended protocol for a CT abdomen with intravenous (IV) and oral contrast typically involves administration of both contrast agents prior to scanning, with IV contrast being essential for optimal assessment of abdominal pathologies, as evident from the study by 1.

Key Considerations

• For oral contrast, patients should drink 1000-1500 mL of diluted iodinated contrast, beginning 60-90 minutes before the scan, with the final cup consumed 30 minutes prior to imaging.
• For IV contrast, non-ionic iodinated contrast is administered at a dose of 1-2 mL/kg (usually 100-150 mL total) via power injector at a rate of 2-3 mL/second immediately before scanning.
• Patients should fast for 4-6 hours before the procedure but may take necessary medications with small sips of water.
• Adequate hydration before and after the procedure is important to protect kidney function.

Special Considerations

• Patients with impaired renal function (eGFR <30 mL/min/1.73m²), history of severe contrast reactions, or certain medical conditions may require protocol modifications or alternative imaging approaches, as noted in the study by 1.
• The use of IV contrast increases the spectrum of detectable pathology in patients with nonlocalized pain, as highlighted in the study by 1.

Evidence-Based Recommendations

• The study by 1 emphasizes the importance of IV contrast in the evaluation of Crohn's disease, with standard CT abdomen and pelvis with IV contrast providing evidence of inflammation of an affected gastrointestinal segment.
• The study by 1 also supports the use of IV contrast in pediatric patients with Crohn's disease, with high agreement between CT and MRE for detection of bowel wall thickening, fluid collections, and fistulae.

Conclusion Not Applicable

Instead, the following key points are emphasized:

• The dual-contrast technique provides optimal visualization of abdominal organs, vasculature, and potential pathologies by enhancing tissue differentiation and improving diagnostic accuracy.
• The recommended protocol should be tailored to individual patient needs, taking into account factors such as renal function, history of contrast reactions, and medical conditions.

From the FDA Drug Label

OMNIPAQUE diluted to concentrations from 6 mg Iodine/mL to 9 mg Iodine/mL administered orally in conjunction with OMNIPAQUE 300 at a concentration of 300 mg Iodine/mL administered intravenously are indicated in adults for use in contrast enhanced computed tomography of the abdomen The recommended oral dosage of OMNIPAQUE diluted to concentrations of 6 mg Iodine/mL to 9 mg Iodine/mL for contrast enhanced computed tomography of the abdomen in adults is 500 mL to 1000 mL. In conjunction with dilute oral administration, the recommended dosage of OMNIPAQUE 300 intravenously is 100 mL to 150 mL. The oral dose is administered about 20 to 40 minutes prior to the intravenous dose and image acquisition.

The recommended protocol for a CT abdomen with intravenous (IV) and oral contrast is:

• Oral Contrast: OMNIPAQUE diluted to concentrations from 6 mg Iodine/mL to 9 mg Iodine/mL, with a recommended dosage of 500 mL to 1000 mL.
• IV Contrast: OMNIPAQUE 300 at a concentration of 300 mg Iodine/mL, with a recommended dosage of 100 mL to 150 mL.
• Administration Timing: The oral dose is administered about 20 to 40 minutes prior to the intravenous dose and image acquisition 2.

From the Research

CT Abdomen with IV and Oral Contrast Protocol

The recommended protocol for a CT abdomen with intravenous (IV) and oral contrast involves several key considerations:

• The oral administration of a dilute positive iodinated contrast agent, such as 2% Gastrografin, is usually necessary to achieve optimal delineation of abdominal and pelvic organs 3.
• The amount of contrast agent administered and the timing of its administration depend on the site of suspected disease within the body 3.
• The simultaneous administration of antiperistaltic agents intravenously is generally unnecessary when utilizing modern fast CT scanners 3.
• Intravenous administration of contrast agent aids characterization of various disease entities and facilitates the recognition of vascular structures, such as veins and arteries in the peripancreatic region 3.

Choice of Oral Contrast Agent

The choice of oral contrast agent can affect the quality of bowel opacification:

• Iohexol has been shown to have fewer artifacts and less bowel lumen heterogeneity compared to diatrizoate and barium sulfate 4.
• Barium sulfate has been found to have a higher frequency of bowel lumen heterogeneity and lower CT attenuation in the ileum compared to iohexol and diatrizoate 4.

Elimination of Routine Oral Contrast

Some studies suggest that eliminating routine oral contrast may not significantly affect diagnostic accuracy:

• A pilot study found that stopping the routine use of oral contrast for CT of the abdomen and pelvis resulted in improved time to completion and emergency department length of stay 5.
• Another study found that CT scan with IV contrast alone was as diagnostic as CT scan with oral and IV contrast in the diagnosis of blunt abdominal trauma 6.

Use of IV Contrast

The use of IV contrast can improve diagnostic accuracy:

• Administration of IV contrast for the first CT abdomen and pelvis was associated with increased detection of urgent findings compared to non-contrast CT 7.
• IV contrast-enhanced CT abdomen and pelvis following an initial non-contrast CT abdomen and pelvis examination better characterized both urgent and non-urgent findings 7.