When to order computed tomography (CT) with intravenous (IV) contrast?

From the Guidelines

CT scans with intravenous (IV) contrast should be ordered in patients with symptomatic hydronephrosis of unknown cause, particularly when there is a high risk of stone passage failure, suspected infection, or flank pain, as it can provide a more comprehensive evaluation and help distinguish between different conditions 1. When deciding to order a CT scan with IV contrast, it is essential to consider the clinical context and the potential benefits of enhanced visualization.

• In patients with renal colic and moderate to severe hydronephrosis, CT with IV contrast can be useful in identifying the cause of obstruction and guiding management 1.
• In cases of suspected infection, such as pyonephrosis, CT with IV contrast can help distinguish between different conditions, although recent contrast administration can affect the density of the collecting system content 1.
• In patients with flank pain, CT with IV contrast can be useful in identifying alternative diagnoses, such as abdominal pathologies or vascular abnormalities 1. Before ordering a CT scan with IV contrast, it is crucial to ensure that the patient has adequate renal function, no history of severe contrast allergy, and is well-hydrated.
• The American College of Radiology recommends using CT with IV contrast in the portal venous phase, 70 seconds after contrast administration, for ideal characterization of solid organ injury, including the genitourinary system 1.
• The administration of oral contrast material is not recommended, as it can delay definitive diagnosis of other injuries 1.
• Noncontrast CT of the abdomen and pelvis should ideally be avoided if there is no contraindication to IV contrast, due to its lower sensitivity for detecting both visceral organ and vascular injuries 1.

From the FDA Drug Label

Because unenhanced scanning may provide adequate diagnostic information in the individual patient, the decision to employ contrast enhancement, which may be associated with risk and increased radiation exposure, should be based upon a careful evaluation of clinical, other radiological, and unenhanced CT findings. The decision to order a CT with IV contrast should be based on a careful evaluation of:

• Clinical findings
• Other radiological findings
• Unenhanced CT findings It is recommended to use contrast enhancement when unenhanced imaging does not provide sufficient delineation between normal loops of the bowel and adjacent organs or areas of suspected pathology 2. Key considerations for ordering a CT with IV contrast include:
• The need for contrast enhancement to provide sufficient diagnostic information
• The potential risks associated with contrast enhancement, such as increased radiation exposure
• The individual patient's clinical and radiological findings 2.

From the Research

CT with IV Contrast Guidelines

The decision to order a CT scan with IV contrast depends on various factors, including the patient's condition and the suspected diagnosis. According to the updated guidelines for intravenous contrast use for CT and MRI 3, IV contrast material is essential for making critical diagnoses in emergency department patients.

Indications for CT with IV Contrast

Some indications for CT with IV contrast include:

• Diagnosing abdominal aortic aneurysms (AAAs) and their complications, such as impending rupture, contained rupture, and infection 4
• Evaluating aortic diseases, including aortic aneurysms and dissection, where CT is a primary imaging modality 5
• Assessing rupture risk in abdominal aortic aneurysms by measuring diameter, tortuosity, thrombus extent, and wall stress 6

Considerations for IV Contrast Administration

When administering IV contrast, considerations include:

• Contrast medium pharmacokinetics and patient factors, such as kidney function and allergy history 7
• Scan timing, which depends on the specific clinical application and the patient's condition 7
• The use of newer contrast agents, which have improved safety profiles and can be used in more patients with fewer precautions 3

Specific Clinical Applications

For specific clinical applications, such as diagnosing aortic diseases, CT with IV contrast is recommended as the initial diagnostic modality 5. In emergency situations, CT with IV contrast can provide critical information for prompt diagnosis and treatment. In non-emergency situations, the strategy for imaging management by CT may differ, and the use of IV contrast should be tailored to the individual patient's needs.