Is a computed tomography (CT) scan with intravenous contrast indicated to assess for vesicointestinal (bladder) fistulas in a patient with Crohn's disease?

From the Guidelines

A CT scan with contrast, specifically a CT cystogram, is the most appropriate imaging choice to assess for bladder fistulas in Crohn's disease, as it provides high sensitivity for detecting fistulas and allows for visualization of the relationship between the bladder, bowel, and surrounding structures 1. The procedure typically involves oral contrast, intravenous contrast, and sometimes rectal contrast to maximize visualization of potential fistulous tracts.

• The patient will need to fast for 4-6 hours before the scan and should be well-hydrated.
• For bladder fistulas specifically, the radiologist may perform a CT cystogram, which involves filling the bladder with diluted contrast material through a catheter.
• This specialized technique helps better identify abnormal connections between the bladder and adjacent bowel segments affected by Crohn's disease.
• The scan is highly sensitive for detecting fistulas because the contrast material will leak from the bladder into the fistulous tract and connected bowel segment. While MRI has excellent soft tissue resolution and is radiation-free, CT with contrast remains valuable for bladder fistula detection due to its speed, availability, and ability to show the relationship between the bladder, bowel, and surrounding structures, as noted in the ACR Appropriateness Criteria for Crohn disease 1. Patients should inform their provider about any allergies to contrast material, kidney problems, or pregnancy before undergoing this procedure, and the use of low-dose techniques, such as tube potential selection, automatic exposure control, and iterative reconstruction, should be considered to minimize radiation exposure, as recommended in the consensus guidelines for CT and MR enterography in patients with small bowel Crohn’s disease 1.

From the Research

CT Scan with Contrast for Bladder Fistulas in Crohn's

• The use of CT scans with contrast to assess for bladder fistulas in Crohn's disease is supported by studies that highlight the importance of imaging in confirming and planning treatment for urinary bladder fistulae 2.
• CT cystography is a useful tool in providing details regarding the fistulous track and the anatomy of the region, which can be crucial in managing bladder fistulas 2.
• In the context of bladder assessment, contrast enhancement is essential, and studies have shown that the corticomedullary phase (CMP) of CT urography provides the highest contrast enhancement, making it preferable for assessing the bladder in the early contrast-enhancing phase 3.
• The diagnostic performance of CT urography has been evaluated in the context of bladder cancer, and it has been shown to be an accurate examination, with the arterial acquisition phase providing the best diagnostic information 4.
• While these studies do not specifically focus on Crohn's disease, they demonstrate the utility of CT scans with contrast in assessing bladder abnormalities, including fistulas, and suggest that this modality could be useful in evaluating bladder fistulas in patients with Crohn's disease 2, 3, 4.