What are the indications for an abdominal pelvic computed tomography (CT) scan with contrast (intravenous iodine or gadolinium)?

From the Guidelines

I strongly recommend an abdominal pelvic CT with contrast for comprehensive evaluation of the abdomen and pelvis, as it provides superior visualization of organ parenchyma, blood vessels, and potential pathologies like tumors, inflammation, infection, or vascular abnormalities that might not be visible on non-contrast studies. This imaging study involves intravenous administration of iodinated contrast material (typically 100-150 mL of contrast agent such as Omnipaque 350 or Isovue 370) to enhance visualization of vascular structures and organs. Patients should fast for 4-6 hours prior to the exam but may take necessary medications with small sips of water. Adequate hydration before and after the procedure is important to help the kidneys process the contrast. The scan takes approximately 15-30 minutes to complete.

Key Considerations

• Patients with impaired kidney function (eGFR <30 mL/min/1.73m²), history of severe contrast allergy, or pregnancy should discuss alternatives with their physician 1.
• Mild allergic reactions occur in about 1-3% of patients.
• The contrast provides superior visualization of organ parenchyma, blood vessels, and potential pathologies like tumors, inflammation, infection, or vascular abnormalities that might not be visible on non-contrast studies.

Indications for Abdominal Pelvic CT with Contrast

• Evaluating conditions such as appendicitis, diverticulitis, abdominal masses, liver lesions, pancreatic disease, and urinary tract abnormalities 1.
• Initial presentation of a patient with Crohn's disease without a known prior diagnosis, particularly in the instance of an acutely ill individual who may be unable to tolerate large amounts of oral contrast for an enterography protocol 1.
• Suspected exacerbation of Crohn's disease 1.
• Blunt trauma, CT of the abdomen and pelvis with IV contrast is recommended, in the portal venous phase, 70 seconds after contrast administration for ideal characterization of solid organ injury, including the genitourinary system 1.
• Acute nonlocalized abdominal pain, CT is a preferred imaging option, and can be performed without and/or with intravenous (IV) contrast and with or without positive oral contrast 1.
• Suspected retroperitoneal bleed, CT is helpful for the diagnosis of retroperitoneal hematoma given its speed, high spatial resolution, and noninvasiveness 1.
• Post-treatment follow-up and active surveillance of clinically localized renal cell carcinoma, CT of the abdomen is the most commonly used method for imaging surveillance after localized RCC ablation 1.
• Indeterminate renal mass, CT abdomen without and with IV contrast, MRI abdomen without and with IV contrast, or US abdomen with IV contrast is usually appropriate for the initial imaging of an indeterminate renal mass in patients without contraindications to either iodinated CT contrast or gadolinium-based MR IV contrast 1.
• Pretreatment staging of urothelial cancer, CTU is generally the most accurate and preferred modality for diagnosis and staging, both local and distant 1.

From the Research

Indications for Abdominal Pelvic Computed Tomography (CT) Scan with Contrast

The indications for an abdominal pelvic CT scan with contrast (intravenous iodine or gadolinium) include:

• Oncological assessment, particularly in patients with renal dysfunction 2
• Evaluation of suspected acute abdominal processes, although the use of contrast may not be necessary in all cases 3
• Abdominal/pelvic CT for various indications, with intravenous contrast being the most frequently used 4

Specific Indications and Contrast Use

Some specific indications and contrast use include:

• Suspected renal colic, where no contrast agent is often used 4
• Viscus perforation, penetrating abdominal trauma, and blunt abdominal trauma, where no contrast agent is sometimes used 4
• Oncological assessment in patients with renal dysfunction, where reduced iodine load abdominal-pelvic CT with 80-kVp and sinogram-affirmed iterative reconstruction (SAFIRE) can be used 2

Contrast-Induced Nephropathy

Contrast-induced nephropathy is a concern in patients undergoing CT scans with contrast, particularly those with renal dysfunction 5

• The use of N-acetylcysteine plus intravenous fluids may not be effective in preventing contrast-induced nephropathy 5
• However, the administration of intravenous fluids in large volumes may help reduce the risk of contrast-induced nephropathy 5

Oral Rehydration and Dehydration

Oral rehydration and dehydration do not appear to affect the incidence of acute adverse reactions to iodinated contrast material for abdominal and pelvic CT 6