When to perform a computed tomography (CT) scan if a urinalysis (UA) shows microscopic hematuria?

From the Guidelines

A CT scan should be performed in patients with microscopic hematuria who have risk factors for urologic malignancy, such as age over 35 years, smoking history, or occupational exposure to chemicals, as recommended by the American College of Radiology 1. When to perform a computed tomography (CT) scan in patients with microscopic hematuria depends on various factors, including the presence of risk factors for urologic malignancy.

Key Considerations

• The American Urological Association defines microhematuria as three or more red blood cells per high power field on microscopic evaluation of urinary sediment from a properly collected, noncontaminated urinalysis 1.
• Patients with gross hematuria have a high association with malignancy, whereas those with microhematuria have a low risk of malignancy, ranging from 2.6% to 4% 1.
• The CT urogram is particularly important for patients with persistent microscopic hematuria on repeat urinalysis, especially when no obvious benign cause has been identified.

Imaging Recommendations

• For patients under 35 without risk factors, renal ultrasound may be considered as an initial imaging study instead of a CT scan.
• Before ordering a CT, it's essential to rule out other causes of microscopic hematuria, such as menstruation, recent urologic procedures, viral illness, or certain medications.
• The CT urogram typically involves non-contrast images followed by contrast-enhanced images with excretory phase to visualize the collecting system.

Risk Classification

• The AUA/SUFU guideline recommends a risk classification system for patients with microhematuria, stratified as low-, intermediate-, or high-risk for genitourinary malignancy, based on factors such as age, sex, smoking, and prior gross hematuria 1.
• Diagnostic evaluation with cystoscopy and upper tract imaging is recommended according to patient risk and involving shared decision-making.

Clinical Evaluation

• All patients diagnosed with microhematuria should undergo a thorough history, physical examination, urinalysis, and serologic testing prior to any initial imaging, as recommended by the American College of Radiology 1.
• Patients with suspected urinary tract infection as a cause of microhematuria should have urine cultures performed, preferably before antibiotic therapy, to confirm an infection.

From the Research

Computed Tomography (CT) Scan for Microscopic Hematuria

• Microscopic hematuria can signify serious disease such as bladder cancer, upper urinary tract urothelial cell carcinoma (UUT-UCC), renal cell cancer, or urinary tract stones 2.
• The American Urological Association recommends complete urologic evaluation for all patients with microscopic hematuria who are over 40 years of age, and younger patients with a history suspicious for urologic disease 3.

Indications for CT Urography

• CT urography is recommended as the initial imaging test for hematuria in patients at high-risk for UCC 2.
• For patients who present with microscopic hematuria, ultrasonography is sufficient to exclude significant upper urinary tract (UUT) disease 4.
• For patients with macroscopic hematuria, the likelihood of finding UUT disease is higher, and a CT urography as a first-line test seems justified 4.

Diagnostic Algorithm

• A diagnostic algorithm for microscopic hematuria involves initial evaluation with renal ultrasound and cystoscopy, followed by intravenous urography (IVU) if microhematuria persists for 3 months without a definitive diagnosis 5.
• The yield of CT urography for upper urinary tract malignancy is low, and it is often performed for patients who do not meet the criteria for radiologic evaluation 6.

Patient Selection

• Patients with asymptomatic microscopic hematuria undergoing CT urography should meet the American Urological Association criteria for radiologic evaluation, which includes more than 3 RBCs per high-power field in the absence of urinary tract infection 6.
• Patients with clinical evidence suggestive of a benign cause of hematuria or prior urologic malignancy should be excluded from CT urography 6.