CT Urography for Microscopic Hematuria Workup
Order CT urography (CTU) with unenhanced images followed by IV contrast-enhanced nephrographic and excretory phases for patients with microscopic hematuria who have risk factors for malignancy. 1
Patient Selection for Imaging
Not all patients with microscopic hematuria require imaging. Do not order imaging for patients without risk factors who have an identified benign cause (vigorous exercise, infection, trauma, menstruation, or recent urologic procedure). 1
Risk Factors Requiring Full Workup:
- Male gender
- Age >35 years
- Smoking history
- Occupational chemical exposure
- History of pelvic irradiation
- Chronic urinary tract infection
- Prior urologic disease
- Irritative voiding symptoms
- Analgesic abuse
- Exposure to chemotherapy or carcinogenic agents
- Chronic indwelling foreign body 1
Important caveat: Anticoagulant therapy does NOT eliminate the need for evaluation—these patients still require full workup. 1
The Optimal CT Protocol
CTU is the imaging study of choice because it evaluates both nephrogenic (kidney parenchymal) and urogenic (collecting system) causes of hematuria. 1
Standard CTU Protocol Components:
- Unenhanced (non-contrast) phase - essential for detecting calculi and baseline assessment 1
- Nephrographic phase - obtained after IV contrast administration 1
- Excretory phase - acquired at least 5 minutes after contrast injection to visualize the collecting system 1
- Thin-slice acquisition with multiplanar reconstructions (maximum intensity projection or 3-D volume rendering) 1
Alternative technique: Split-bolus protocol uses an initial contrast loading dose followed by a second dose to obtain a combined nephrographic-excretory phase. 1
Why CTU Outperforms Other Modalities
CTU demonstrates superior diagnostic accuracy with pooled sensitivity of 96% and specificity of 99% for detecting urothelial malignancy. 1
Comparative Performance:
- Upper tract lesions (kidneys/ureters): CTU accuracy 99.6% vs. IVU 84.9% 1
- Lower tract lesions (bladder): CTU specificity 98.8% and accuracy 97.2% 1
- Better than MR urography: CTU provides superior visibility of urothelial structures and improved diagnostic confidence 1
What NOT to Order
Do not order standard "CT abdomen and pelvis with contrast" - this is NOT the same as CTU and lacks the critical unenhanced and excretory phases needed to properly evaluate the urinary tract. 1
Avoid these inadequate alternatives:
- Ultrasound alone - lower sensitivity than CTU for urinary tract abnormalities 1
- Intravenous urography (IVU) - obsolete with low sensitivity for renal masses 1
- Plain radiographs (KUB) - not appropriate for hematuria evaluation 1
- MR urography - decreased spatial resolution, misses small calculi and small urothelial lesions 1
Special Consideration: Young Patients
For patients <50 years old with microscopic hematuria and no risk factors, unenhanced CT alone may be sufficient. 2, 3, 4 In this population, the risk of upper urinary tract malignancy is <1.1%, and 91-95% of clinically significant findings are visible on unenhanced images alone. 2, 3, 4
This approach reduces radiation exposure and eliminates contrast-related risks in younger patients. 2, 3 However, if the patient has risk factors or predisposing medical conditions, proceed with full CTU protocol. 3
Pregnancy Exception
Do not use CTU in pregnant patients due to fetal radiation exposure. 1 The malignancy rate in pregnant women with microscopic hematuria is extremely low. 1 If imaging is absolutely necessary, ultrasound of kidneys and bladder is the appropriate choice. 1
Clinical Context
The malignancy risk with microscopic hematuria is only 2.6-4%, and most cases never identify a cause. 1 However, the primary goal of imaging is to exclude malignancy, which can occur anywhere in the urinary tract. 1 CTU's comprehensive evaluation of the entire urinary system makes it the definitive test when imaging is indicated. 1