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Microscopic hematuria

Definition
Microscopic hematuria is defined as the presence of ≥ 2 RBCs per high-power field on microscopic evaluation of a properly collected urine specimen.
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Pathophysiology
The pathophysiology of microscopic hematuria involves the presence of RBCs in the urine, which can be due to a variety of causes. These can include benign processes, kidney disease, genitourinary malignancy, and other renal or urinary tract disorders.
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Epidemiology
The prevalence of microscopic hematuria in the US is estimated at 20,100 per 100,000 population.
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Disease course
The clinical course of microscopic hematuria often involves an initial incidental discovery, followed by investigations to determine the source. This can include a physical examination, history taking, and diagnostic tests such as cystoscopy and renal ultrasound, depending on the patient's risk for malignancy.
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Prognosis and risk of recurrence
The prognosis of microscopic hematuria is generally good, but it can vary depending on the underlying cause.
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Key sources
The following summarized guidelines for the evaluation and management of microscopic hematuria are prepared by our editorial team based on guidelines from the American Urological Association (AUA/SUFU 2020), the American College of Radiology (ACR 2020), the American College of Obstetricians and Gynecologists (ACOG/AUGS 2017), and the American Urological Association (AUA 2012).
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Guidelines

1.Screening and diagnosis

Definitions
Define microhematuria as ≥ 3 RBCs/hpf on microscopic evaluation of a single, properly collected urine specimen.
B
Do not diagnose microhematuria by positive dipstick testing alone. Obtain formal microscopic evaluation of the urine in patients with a positive urine dipstick test (trace blood or greater).
D
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2.Classification and risk stratification

Risk stratification
As per AUA 2020 guidelines:
Categorize patients presenting with microhematuria as low-, intermediate-, or high-risk for genitourinary malignancy following the initial evaluation:
Situation
Guidance
Low (meeting all criteria)
Females aged < 50 years, males aged < 40 years
Never-smoker or < 10 pack-years
10 RBC/hpf on a single urinalysis
No risk factors for urothelial cancer
Intermediate (meeting any of the criteria)
Females aged 50-59 years, males aged 40-59 years
10-30 pack-years of smoking
11-25 RBC/hpf on a single urinalysis
Low-risk patient with no prior evaluation and 3-10 RBC/hpf on repeat urinalysis
Additional risk factors for urothelial cancer (irritative LUTS, prior pelvic radiation therapy, prior cyclophosphamide/ifosfamide chemotherapy, family history of urothelial cancer or Lynch syndrome, occupational exposures to benzene chemicals or aromatic amines, such as rubber, petrochemicals, dyes, chronic indwelling foreign body in the urinary tract)
High (meeting any of the criteria)
Age ≥ 60 years
> 30 pack-years of smoking
> 25 RBC/hpf on a single urinalysis
History of gross hematuria
B
Re-classify low-risk patients as intermediate- or high-risk if they initially elected not to undergo cystoscopy or upper tract imaging and were found to have microhematuria on repeat urine testing.
B

3.Diagnostic investigations

Initial evaluation
As per SUFU 2020 guidelines:
Elicit history and perform a physical examination in patients with microhematuria to assess risk factors for genitourinary malignancy, renal disease, gynecologic and non-malignant genitourinary causes of microhematuria.
B
Use appropriate physical examination techniques and tests in patients with findings suggestive of a gynecologic or non-malignant urologic etiology to identify such an etiology.
B

More topics in this section

  • Initial imaging and cystoscopy

  • CT/MR urography

  • Retrograde pyelography

  • Urine cytology and urine markers

4.Specific circumstances

Patients with family history of renal malignancy: obtain upper tract imaging in patients with microhematuria with a family history of renal cell carcinoma or a known genetic renal tumor syndrome, regardless of risk category.
E

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  • Patients on antithrombotics

5.Follow-up and surveillance

Indications for specialist referral: refer patients with microhematuria for nephrologic evaluation if a renal disease is suspected, concomitantly obtain a risk-based urologic evaluation.
B

More topics in this section

  • Serial assessment

  • Evaluation of persistent or recurrent hematuria