What is the cause of hematuria (blood in urine) as evaluated by a computed tomography (CT) scan of the abdominal and pelvic region with contrast, focusing on the renal (kidney) structures?

From the Guidelines

For a patient with hematuria requiring evaluation, a computed tomography urography (CTU) with and without intravenous (IV) contrast is usually the most appropriate initial imaging study, as it provides detailed images of the kidneys, ureters, bladder, and surrounding structures to identify potential causes of blood in the urine. This recommendation is based on the American College of Radiology (ACR) Appropriateness Criteria for hematuria, which suggests that CTU with and without IV contrast is appropriate for the initial imaging of microhematuria in patients with risk factors and for the initial imaging of gross hematuria 1. The use of IV contrast material, typically 100-150 mL of iodinated contrast, allows for better visualization of masses, vascular structures, and inflammatory changes that might be causing the hematuria.

When performing the CTU, patients should be instructed to fast for 4-6 hours before the procedure but continue to drink clear fluids, and they should inform their provider about any allergies to contrast, kidney problems, or if they're taking metformin. The procedure takes approximately 15-30 minutes, and patients may feel a warm sensation when contrast is injected. The CTU with and without IV contrast provides superior tissue differentiation compared to non-contrast studies, allowing for the detection of kidney stones, tumors, infections, vascular abnormalities, and other urinary tract pathologies with high sensitivity.

Some key points to consider when evaluating hematuria with CTU include:

• The importance of using IV contrast to visualize the urinary tract and surrounding structures
• The need to image the kidneys, ureters, and bladder to identify potential causes of hematuria
• The ability of CTU to detect a range of urinary tract abnormalities, including renal masses, genitourinary trauma, and specific aspects of renal infection
• The limitations of non-contrast CT studies in detecting certain types of urinary tract pathology, such as kidney stones and vascular abnormalities 1.

Overall, the use of CTU with and without IV contrast is a highly effective imaging modality for evaluating hematuria, and it should be considered the initial imaging study of choice for patients with this condition, particularly those with risk factors or gross hematuria.

From the Research

Causes of Hematuria

• Hematuria can be caused by various factors, including urinary tract infection, urolithiasis, malignancies, benign prostatic hyperplasia, and nephropathies 2
• It can present as macroscopic hematuria or microscopic hematuria due to either glomerular or non-glomerular disorders 3
• Renal hemangiomas are a likely cause of chronic benign hematuria, particularly in young patients 4

Diagnostic Evaluation

• A computed tomography (CT) scan of the abdominal and pelvic region with contrast can be used to evaluate hematuria, focusing on the renal structures 2, 5
• The use of iodinated contrast media in CT scans can cause renal toxicity, especially in patients with pre-existing renal failure 6
• To minimize the risk of renal toxicity, the recommendation is to administer the least amount of contrast possible and ensure appropriate volume expansion 6

Renal Structure Evaluation

• A CT scan can help identify abnormalities in the renal structures, such as tumors, cysts, or stones, which can cause hematuria 2, 5
• The scan can also help evaluate the renal function and detect any signs of nephropathy or other renal diseases 3
• In some cases, additional tests such as ultrasound, magnetic resonance urography, or cystoscopy may be necessary to further evaluate the cause of hematuria 2, 5