From the Guidelines
A CT urogram with contrast is the most accurate and preferred modality for diagnosis and staging of urothelial cancer, particularly for localizing, locoregional staging, and detecting distant metastases, as supported by the European Association of Urology guidelines and several studies, including a recent review by Mirmomen et al 1.
Key Points
- CT urogram with contrast provides detailed images of the kidneys, ureters, and bladder, allowing for evaluation of these structures and detection of abnormalities.
- The contrast material, typically an iodine-based solution, is injected into a vein and helps highlight the urinary system as it filters through the kidneys and collects in the bladder.
- This test is particularly useful for diagnosing conditions such as kidney stones, tumors, obstructions, congenital abnormalities, and urinary tract infections.
- Patients should inform their healthcare provider about any allergies to contrast materials, as reactions can occur, and those with kidney problems may need special consideration since contrast can sometimes affect kidney function.
- Preparation typically involves fasting for several hours before the exam and drinking plenty of water afterward to help flush the contrast material from the body.
- The entire procedure usually takes about 30-60 minutes to complete.
Benefits and Risks
- Benefits: CT urogram with contrast is highly sensitive and specific for detecting urothelial cancer, with a pooled sensitivity of 96% and a specificity of 99% for identifying UC, as reported in a meta-analysis and systematic review 1.
- Risks: harms associated with CT urography include nephropathy from intravenous contrast and the rare but real risk for life-threatening hypersensitivity reactions to contrast, as well as the potential longer-term harm of ionizing radiation exposure, which may increase the risk for cancer, as noted in a study published in the Annals of Internal Medicine 2.
Clinical Considerations
- CT urogram with contrast is essential for evaluating nonfunctioning/obstructed kidneys that would not excrete the contrast medium required for excretory urography.
- The test can also evaluate distant metastases, which can occur in approximately 22.4% of patients with UTUC, with the most common metastatic sites being lung, distant lymph nodes, bone, liver, and adrenal gland, as reported in a study published in the Journal of the American College of Radiology 3.
- A recent review by Mirmomen et al 1 demonstrated that CTU has a 91% diagnostic accuracy in detecting UCs, although it may miss very small or flat lesions that are more easily detected by cystoscopy.
From the Research
CT Urogram with Contrast
- CT urography (CTU) is a diagnostic imaging technique that uses computed tomography (CT) to visualize the urinary tract, and it often involves the use of contrast media to enhance image quality 4, 5, 6.
- The use of contrast media in CTU is crucial for identifying primary urothelial malignancies, benign urinary tract conditions, and associated abdominopelvic pathologies 6.
- A differential approach using a one-, two-, or three-phase protocol is proposed for CTU, whereby the clinical indication and the patient population determine which CTU protocol is employed, and either a combined nephrographic-excretory phase following a split-bolus intravenous injection of contrast medium or separate nephrographic and excretory phases following a single-bolus injection can be used 4.
- The choice of contrast media for CTU depends on various factors, including the patient's renal function and potential allergies to iodinated contrast media, and alternative contrast media such as carbon dioxide, gadolinium, and dilute iodinated contrast media may be used in certain cases 7, 8.
- Recent studies have focused on optimizing CTU protocols to minimize radiation dose and maximize urinary tract distension and opacification, while also ensuring the safe use of contrast media in patients with chronic kidney disease 6, 8.