Multiphasic CT Urography Protocol for Hematuria Evaluation
Patient Preparation
Patients should be adequately hydrated (oral or intravenous fluids) 2-4 hours before the examination to ensure optimal opacification of the collecting system and ureters. 1, 2 No fasting is required, and maintaining hydration helps reduce the risk of contrast-induced nephropathy while improving image quality. 1
Screen for contraindications including renal insufficiency (serum creatinine/eGFR), contrast allergy history, pregnancy, and metformin use. 1 Patients with eGFR <30 mL/min/1.73m² or severe contrast allergies should be considered for alternative imaging such as MR urography. 1
Contrast Administration
Administer 100-150 mL of low-osmolar or iso-osmolar iodinated contrast intravenously at 2-4 mL/second. 2, 3 The contrast dose and injection rate are optimized to achieve adequate enhancement of both renal parenchyma and urothelial structures while minimizing nephrotoxicity risk. 1, 2
The risk of severe contrast reactions is extremely low per American College of Radiology criteria, though contrast-induced nephropathy occurs in up to 2% of general population patients and ≥20% of high-risk patients with congestive heart failure, diabetes, or chronic kidney disease. 1
Required Imaging Phases
Phase 1: Unenhanced (Non-Contrast) Scan
Acquire images from the kidneys through the bladder before contrast administration to detect renal calculi, which appear as high-density structures and are the most common cause of hematuria. 2, 4, 3 This phase is essential because contrast obscures calculi on subsequent phases. 2, 3
Unenhanced imaging also establishes baseline attenuation values for characterizing renal masses and detecting hemorrhage. 2, 3
Phase 2: Nephrographic Phase
Obtain images 80-100 seconds after contrast injection to capture peak renal parenchymal enhancement, which optimally demonstrates renal masses, renal cell carcinoma, and other parenchymal abnormalities. 2, 4, 3
All upper tract urothelial cell carcinomas are visible on the nephrographic phase, making this the most critical phase for detecting renal parenchymal disease. 4 This phase also provides excellent evaluation of other abdominal organs. 2, 3
Phase 3: Excretory (Delayed) Phase
Acquire thin-section images 5-15 minutes after contrast injection (timing adjusted based on renal function) from the kidneys through the bladder to visualize the contrast-opacified collecting systems, ureters, and bladder. 1, 2, 3
This delayed phase is mandatory for detecting urothelial lesions, filling defects, and upper tract transitional cell carcinoma, as it demonstrates the urinary tract distended with excreted contrast material. 1, 2, 3 The American College of Radiology specifically notes that high-resolution imaging during the excretory phase is required for adequate hematuria evaluation. 1
Some protocols include prone imaging during the excretory phase to improve ureteral distention and opacification, though this is optional. 2
Technical Parameters
Use multi-detector CT with thin collimation (≤3 mm) to allow multiplanar reconstructions and improved detection of small urothelial lesions. 2, 5 Coronal and sagittal reformations enhance visualization of the ureters and collecting systems. 2
The median effective radiation dose for standard 3-phase CT urography is 20-30 mSv, though this varies substantially (range 6-90 mSv) depending on scanner and protocol. 1 This represents one of the highest radiation exposures among common CT protocols, with an estimated lifetime attributable cancer risk of 4 cases per 1000 patients. 1
Diagnostic Performance
Multiphasic CT urography demonstrates 96% sensitivity and 99% specificity for detecting urothelial malignancy, with 99.6% accuracy for upper tract lesions and 97.2% accuracy for bladder lesions. 4, 5 This superior diagnostic performance makes CT urography the gold standard, replacing the previous combination of ultrasound and intravenous pyelography. 1, 5
CT urography permits comprehensive evaluation of hematuria patients in a single examination, detecting renal cell carcinoma, transitional cell carcinoma, and urolithiasis simultaneously. 2, 5, 3, 6
Clinical Context
Multi-detector CT urography with all three phases (unenhanced, nephrographic, excretory) had the most consistent and highest sensitivities and specificities for detecting lesions of the renal parenchyma and upper tracts in patients with asymptomatic microhematuria. 1 The American Urological Association gives this approach its highest recommendation for maximizing diagnostic certainty. 1
In a consecutive series of 771 hematuria patients, CT urography identified tumors/complex cysts in 18%, calculi in 9%, and other disease in 15%, with lesions found more frequently in visible hematuria (48%) versus non-visible hematuria (29%). 6