What is the recommended initial imaging study for a patient presenting with gross hematuria (blood in the urine)?

Imaging for Gross Hematuria

CT urography (CTU) without and with IV contrast is the recommended first-line imaging study for patients presenting with gross hematuria. 1

Rationale for CTU as First Choice

CTU without and with IV contrast offers several advantages:

• Excellent sensitivity (96%) and specificity (99%) for detecting urothelial malignancy 1
• Superior detection of small lesions compared to ultrasound or non-contrast studies 1
• Comprehensive evaluation of the entire urinary tract in a single examination 1
• Accuracy of 99.6% for detecting upper tract lesions 1
• Ability to detect urinary calculi, renal parenchymal abnormalities, and masses 2

The American College of Radiology (ACR) Appropriateness Criteria explicitly states that "CTU without and with IV contrast is usually appropriate for the initial imaging of gross hematuria" 2.

CTU Protocol Components

A complete CTU examination includes:

• Unenhanced phase (for calculi detection)
• Nephrographic phase (for renal parenchymal assessment)
• Excretory phase (for optimal visualization of the collecting system) 1

Alternative Imaging Options

In specific patient populations, alternative imaging may be appropriate:

1. MR Urography (MRU):

   • For patients with renal insufficiency or contrast allergy 1
   • Comparable accuracy to CT for renal masses
   • Limitations include decreased spatial resolution and difficulty detecting small calculi 1

2. Ultrasound:

   • First-line for pregnant patients 2, 1
   • Limited sensitivity (35.3-50.7%) compared to CT 2, 1
   • Not recommended as first-line for non-pregnant adults due to poor sensitivity 1

Special Considerations

• Age and Risk Factors: For patients under 35 years without risk factors, CT abdomen and pelvis without IV contrast may be sufficient 1, 3
• Pregnancy: Ultrasound of kidneys and bladder is recommended to avoid radiation exposure 2, 1
• Trauma Context: In cases of blunt trauma with gross hematuria, CT with IV contrast is recommended, with consideration of CT cystography if bladder injury is suspected 2, 4

Common Pitfalls to Avoid

1. Relying solely on ultrasound in non-pregnant adults: Despite being radiation-free, ultrasound has limited sensitivity for detecting significant urinary tract pathology 2, 1

2. Skipping contrast phases: All three phases (unenhanced, nephrographic, and excretory) are necessary for complete evaluation 1

3. Overlooking bladder assessment: While upper tract evaluation is important, thorough bladder assessment is critical as bladder cancer is a common cause of gross hematuria 1

4. Assuming benign etiology in young patients: While less common, malignancy can occur in younger patients with gross hematuria 3

By following these evidence-based recommendations, clinicians can ensure appropriate imaging evaluation of patients presenting with gross hematuria, optimizing detection of significant pathology while minimizing unnecessary radiation exposure.