From the Guidelines
A CT cystogram is performed by inserting a urinary catheter into the bladder and instilling contrast material, typically a diluted iodine-based solution, to fill the bladder completely, followed by CT imaging to detect bladder ruptures or leaks. The procedure is crucial in evaluating bladder injuries, particularly in trauma patients with gross hematuria and pelvic fracture, as emphasized in the urotrauma guideline 1. According to the guideline, retrograde cystography, which includes CT cystography, is the technique of choice to diagnose bladder injury, with plain film and CT cystography having similar specificity and sensitivity.
The technique for CT cystogram involves using dilute water-soluble contrast to prevent artifacts from obscuring visualization, as stated in the urotrauma guideline 1. Simply clamping a Foley catheter to allow excreted IV-administered contrast to accumulate in the bladder is not appropriate, as it will not provide adequate bladder distention and may result in missed bladder injuries. The choice of imaging modality, whether plain film or CT cystography, is largely left to clinician preference, equipment availability, imaging requirements for other associated injuries, patient stability, and ease of testing.
In line with the more recent guidelines on kidney and uro-trauma 1, retrograde cystography, including CT-scan, represents the diagnostic procedure of choice in bladder injuries, and should be always performed in hemodynamically stable or stabilized patients with suspected bladder injury. The guideline also notes that intravenous contrast-enhanced CT-scan with delayed phase is less sensitive and specific than retrograde cystography in detecting bladder injuries. Therefore, when it comes to diagnosing bladder injuries, particularly in the context of trauma, CT cystogram is a preferred method due to its ability to provide detailed images of the bladder and surrounding structures, allowing for better visualization of injuries and their exact location, as supported by the highest quality and most recent evidence 1.
From the Research
CT Cystogram Procedure
A CT cystogram is a medical imaging test used to evaluate the bladder and urethra. The procedure involves:
- Filling the bladder with a contrast agent through a catheter
- Taking CT scans of the bladder and urethra to visualize any injuries or abnormalities
- The contrast agent can be either iodine-based or gadolinium-based, depending on the patient's sensitivity or allergy to iodine 2, 3, 4, 5
Types of Contrast Agents
There are two main types of contrast agents used in CT cystography:
- Iodine-based contrast agents: commonly used, but may cause allergic reactions in some patients 6, 2, 5
- Gadolinium-based contrast agents: can be used as an alternative to iodine-based agents in patients with iodine sensitivity or allergy 2, 3, 4, 5
Imaging Techniques
Different imaging techniques can be used to enhance the visibility of the contrast agent:
- Single-energy CT scans: can be used to visualize the contrast agent, but may not provide the best contrast enhancement 2
- Dual-energy CT scans: can provide better contrast enhancement and are useful for visualizing gadolinium-based contrast agents 2
- Virtual monoenergetic images (VMIs): can be generated from dual-energy CT scans to provide the highest contrast enhancement 2