What imaging is recommended to investigate a patient with brown-colored urine and pneumaturia?

In the context of a patient presenting with brown-colored urine and pneumaturia, a CT scan of the abdomen and pelvis is the most appropriate imaging modality. This clinical presentation suggests the possibility of a fistula, likely between the gastrointestinal tract and the urinary system, which can be complicated by conditions such as diverticulitis or colorectal cancer.

A CT abdomen and pelvis provides comprehensive information, allowing for the assessment of potential underlying causes leading to these symptoms. It can visualize the abdominal and pelvic organs, identify any abscesses, detect air in the urinary bladder, and clarify the relationship between different structures, all of which are crucial for determining the best management strategy.

In contrast, while chest X-rays (CXR) and abdominal X-rays (AXR) can provide some information, they are limited in their ability to evaluate the soft tissue structures involved and may miss complex pathologies that a CT scan would easily capture. Ultrasound can be useful for assessing certain urinary conditions, but it would not be definitive in investigating potential gastrointestinal causes of pneumaturia. A plain X-ray of the abdomen also has limited utility in diagnosing this particular scenario, as it does not provide detailed imaging of soft tissue structures.

Thus, a CT abdomen and pelvis stands out as the