From the Guidelines
CT chest with contrast is preferred over CT chest without contrast in clinical situations such as suspected parapneumonic effusion or empyema, particularly in cases of recent pneumonia, as it allows for better visualization of pleural enhancement, pleural thickening, and other key diagnostic features 1.
Key Clinical Scenarios
- Suspected parapneumonic effusion or empyema in the context of recent pneumonia, where contrast-enhanced CT can help identify pleural enhancement, a key diagnostic feature with high sensitivity and specificity for empyema 1.
- Conditions where differentiation between vascular structures and adjacent soft tissue is crucial, although this specific scenario is not directly addressed in the provided evidence.
Rationale
The use of CT chest with contrast in these scenarios is supported by recent guidelines and studies, including the American Association for Thoracic Surgery consensus guidelines and a meta-analysis highlighting the importance of pleural enhancement in diagnosing empyema 1. The technical aspect of acquiring the CT scan 60 seconds after the IV contrast bolus is also noted to optimize visualization of the pleura 1.
Considerations
While the provided evidence strongly supports the use of CT chest with contrast in specific clinical situations like suspected parapneumonic effusion or empyema, it's essential to consider the patient's overall clinical context, including renal function and history of contrast allergy, to weigh the benefits and risks of contrast administration 1.
From the Research
Clinical Situations for CT Chest with Contrast
A CT chest with contrast is preferred over a CT chest without contrast in the following clinical situations:
- Diagnosis of acute aortic syndrome and pulmonary embolism, as computed tomography has become the de facto clinical reference standard for diagnosis 2
- Detection of pulmonary embolism, where CT pulmonary angiography offers high accuracy, speed of acquisition, and widespread availability 3
- Planning of endovascular therapy for acute pulmonary embolism, where CT pulmonary angiography aids in visualizing the number and distribution of emboli, determining ideal intra-procedural catheter position for treatment, and signs of right heart strain 3
- Evaluation of patients with acute, potentially life-threatening chest pain, where triage is challenging and computed tomography is essential for diagnosis 2
Contrast Medium Protocols
The use of contrast medium in chest CT is an important image quality factor, and there is no clear evidence or guidelines on contrast medium strategies, thus a consensus approach is needed 4. The administration of contrast medium can affect image quality, and different protocols are used in various institutions 4.
Limitations of Non-Contrast CT
While non-contrast chest CT scans can lead to the diagnosis of pulmonary embolism through signs such as the hyperdense pulmonary artery sign and pulmonary infarction, contrast-enhanced CT scans are generally preferred for diagnosis 5, 3. Additionally, non-contrast CT scans may not provide sufficient information for planning endovascular therapy 3.