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 IV contrast is recommended for CT abdomen scans, while oral contrast may be used on a case-by-case basis, considering the patient's condition and the suspected diagnosis. For IV contrast, iodinated agents such as iohexol (Omnipaque) or iopamidol (Isovue) are typically administered at a dose of 1-2 mL/kg with a standard adult dose of 100-150 mL, injected at a rate of 2-5 mL/second, as suggested by 1. Timing is crucial, with arterial phase imaging occurring 20-30 seconds post-injection, portal venous phase at 60-70 seconds, and delayed phases at 3-5 minutes.

Patient Considerations

When considering the use of oral contrast, it is essential to weigh the benefits against the potential drawbacks, such as delayed scan acquisition and departmental throughput, as noted in 1. Patient considerations include screening for contraindications such as renal impairment (eGFR <30 mL/min/1.73m²), previous contrast reactions, metformin use, pregnancy, and hyperthyroidism. Adequate hydration is essential before and after contrast administration to reduce nephrotoxicity risk. For patients with mild to moderate renal impairment, lower contrast doses and additional hydration may be appropriate, as suggested by 1.

Emergency Scans

Emergency scans may require abbreviated oral contrast protocols or proceed without oral contrast if the clinical situation demands immediate imaging, as indicated in 1. The use of IV contrast can provide valuable information in the diagnosis of various conditions, including gastric disease, as noted in 1 and 1.

Key Points

• IV contrast is recommended for CT abdomen scans
• Oral contrast may be used on a case-by-case basis
• Patient considerations, such as renal impairment and previous contrast reactions, should be taken into account
• Emergency scans may require abbreviated oral contrast protocols or proceed without oral contrast
• IV contrast can provide valuable information in the diagnosis of various conditions, including gastric disease, as supported by 1.

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 been established in pediatric patients, but repeat dosing has not been studied 2. 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.