What is the role of renal ultrasound in evaluating patients with hematuria?

From the Guidelines

Renal ultrasound is the recommended initial imaging modality for evaluating patients with hematuria, as it is non-invasive, does not use radiation, and is relatively inexpensive. According to the most recent guidelines, including the 2025 update to microhematuria: AUA/SUFU guideline 1, renal ultrasound should be performed in most patients with unexplained hematuria to evaluate the kidneys, ureters, and bladder. This imaging modality can effectively detect kidney masses, stones, hydronephrosis, and structural abnormalities that may cause bleeding. However, it has limitations in detecting small lesions (<1 cm), urothelial tumors, and some urinary tract abnormalities.

Key Points to Consider

• The sensitivity of renal ultrasound varies depending on the pathology being evaluated, with excellent detection of hydronephrosis and renal cysts but less sensitivity for small solid masses and ureteral abnormalities 1.
• Patients with risk factors for urological malignancies or persistent unexplained hematuria may require additional imaging such as CT urography or cystoscopy even after a normal ultrasound 1.
• Clinicians should consider patient factors such as age, smoking history, and occupational exposures when determining if additional imaging beyond ultrasound is necessary 1.
• The ACR Appropriateness Criteria for hematuria recommend a thorough history, physical examination, urinalysis, and serologic testing prior to any initial imaging 1.

Limitations and Additional Considerations

• Renal ultrasound has a low sensitivity for detecting upper tract urothelial carcinoma (UTUC) and renal cortical tumors, with a sensitivity of 33% and specificity of 96% reported in one study 1.
• CT urography provides excellent delineation of the excretory urinary tract and is very sensitive for urinary stones, but involves ionizing radiation and iodine-based IV contrast 1.
• Urine cytology and urine-based tumor markers (UBTMs) may be used to assist in cases where the test results may inform the decision regarding the utility of cystoscopy, but renal and bladder ultrasound should still be performed in these cases 1.

From the Research

Role of Renal Ultrasound in Evaluating Patients with Hematuria

• Renal ultrasound is one of the imaging modalities used to evaluate patients with hematuria, although its role is not as prominent as CT urography in high-risk patients 2, 3.
• The sensitivity and specificity of ultrasound scans for detecting genitourinary tumors or calculi are 50% and 95%, respectively 4.
• Ultrasound may be useful in detecting renal parenchymal abnormalities, such as masses or calculi, but it is not as effective as CT urography in evaluating the urothelium 3, 5.
• In patients with microscopic hematuria, a noncontrast CT or ultrasound study may be considered, especially in those under 40 years old 4.
• However, CT urography is generally recommended as the initial imaging test for hematuria in patients at high-risk for urothelial cell carcinoma (UCC) due to its high diagnostic accuracy 2, 6.

Limitations of Renal Ultrasound

• Renal ultrasound may not provide a comprehensive evaluation of the urinary tract, unlike CT urography, which can image the kidneys, ureters, and bladder 2, 5.
• Ultrasound may not be as effective in detecting urothelial disease or small calculi, which can be better visualized with CT urography 3, 6.
• The use of renal ultrasound as a replacement for CT urography or other imaging tests is not recommended in high-risk patients with hematuria 2.