What are the guidelines for using intravenous (IV) and oral contrast for a computed tomography (CT) abdomen scan, including dosing and patient considerations?

From the Guidelines

The use of both IV and oral contrast for CT abdomen scans is recommended, with IV contrast administered at a dose of 1-2 mL/kg and oral contrast using diluted barium sulfate or water-soluble iodinated agents, to balance diagnostic quality with patient safety considerations. When considering the use of contrast for CT abdomen scans, it is essential to weigh the benefits of improved diagnostic accuracy against potential risks, such as contrast-induced nephropathy or allergic reactions 1. Key considerations include:

• Patient screening for renal function, previous contrast reactions, metformin use, pregnancy status, and thyroid disease
• Adequate hydration before and after contrast administration to prevent contrast-induced nephropathy
• The specific clinical indication, as some cases like suspected appendicitis or renal stones may not require contrast, while others like tumor staging or vascular assessment benefit significantly from contrast enhancement 1
• The choice of IV contrast agent, such as iodinated agents like iohexol or iopamidol, and the timing of imaging, with arterial phase occurring 20-35 seconds post-injection and portal venous phase at 60-70 seconds 1
• The use of oral contrast, which can help identify conditions like diverticulitis or inflammatory bowel disease, but may not be necessary for all indications 1 In general, the most recent and highest quality study, 1, suggests that the use of IV contrast with a neutral oral contrast like water or dilute barium suspension is preferred for suspected gastric disease, as it allows for assessment of submucosal edema, mucosal hyperenhancement, and other findings. However, the specific protocol may vary depending on the clinical context and patient factors, and should be individualized to balance diagnostic quality with patient safety considerations.

From the FDA Drug Label

The recommended dose for adult and pediatric patients, including term neonates, is 0.2 mL/kg (0. 1 mmol/kg) administered as a rapid intravenous infusion (10 mL/min to 60 mL/min) or bolus (greater than 60 mL/min).

Table 1: Recommended Volume of Gadoteridol Injection by Body Weight Body Weight (kg) Volume to be Administered (mL) 2.5 0. 5 5 1 10 2 20 4 30 6 40 8 50 10 60 12 70 14 80 16 90 18 100 20 110 22 120 24 130 26 140 28 150 30

The guidelines for using intravenous (IV) contrast for a computed tomography (CT) abdomen scan are as follows:

• Dosing: The recommended dose is 0.2 mL/kg (0.1 mmol/kg) administered as a rapid intravenous infusion (10 mL/min to 60 mL/min) or bolus (greater than 60 mL/min) 2.
• Administration: Visually inspect the contrast agent for particulate matter and discoloration prior to use. Do not administer the solution if it is discolored or particulate matter is present. Inject at least a 5 mL normal saline flush immediately after the contrast agent to ensure complete administration 2.
• Patient considerations: The safety and efficacy of the contrast agent have not been established in pediatric patients with poorly visualized CNS lesions. In patients with impaired renal function, the serum half-life of the contrast agent is prolonged 2.

Note: There is no information in the provided drug labels about oral contrast.

From the Research

Guidelines for CT Abdomen with IV and Oral Contrast

The use of intravenous (IV) and oral contrast in computed tomography (CT) abdomen scans is a common practice to enhance the diagnostic accuracy of various abdominal pathologies.

• The American College of Radiology (ACR) provides guidelines for the use of IV contrast in CT scans, including those for the abdomen and pelvis 3.
• Studies have shown that the use of IV contrast alone can be as effective as the combination of IV and oral contrast in diagnosing certain conditions, such as appendicitis 4 and blunt abdominal trauma 5.
• The administration of IV contrast has been associated with increased detection of urgent findings compared to non-contrast CT scans 6.

Dosing and Patient Considerations

When using IV and oral contrast in CT abdomen scans, several factors should be considered:

• The dosage of IV contrast depends on the patient's weight, kidney function, and the specific contrast agent used 3.
• Oral contrast is often used to opacify the bowel and help distinguish it from other abdominal structures, but its use may be limited in certain situations, such as in patients with suspected bowel obstruction or those who are unable to tolerate oral intake 7, 4.
• Patient considerations, such as allergies to contrast agents, kidney function, and pregnancy or breastfeeding status, should be taken into account when deciding whether to use IV and/or oral contrast 3.

Diagnostic Accuracy

The diagnostic accuracy of CT abdomen scans with IV and oral contrast has been evaluated in several studies:

• A study published in the World Journal of Surgery found that the use of IV contrast alone was correct in 92.5% of cases, while the combination of IV and oral contrast was correct in 94.6% of cases 7.
• Another study published in the Chinese Journal of Traumatology found that CT scans with IV contrast alone had a sensitivity and specificity of 96.6% and 92.84%, respectively, in diagnosing blunt abdominal trauma, which was comparable to the combination of IV and oral contrast 5.
• A study published in the American Journal of Emergency Medicine found that CT scans with IV contrast alone had a sensitivity and specificity of 100% and 98.6%, respectively, in diagnosing appendicitis, which was comparable to the combination of IV and oral contrast 4.