From the Guidelines
Asymptomatic hematuria necessitates a comprehensive evaluation to identify potential underlying conditions, and clinicians should prioritize a thorough workup, including urinalysis confirmation, urine culture, and imaging studies, to rule out serious diseases, as recommended by the American College of Physicians 1. The initial assessment of asymptomatic hematuria should involve a detailed medical history, including inquiries about smoking, chemical exposure, and prior urologic disorders, as these factors increase the risk of significant disease 1. Key considerations in the evaluation of asymptomatic hematuria include:
- Confirming the presence of hematuria through microscopic urinalysis, which demonstrates 3 or more erythrocytes per high-powered field 1
- Ordering imaging studies, such as renal ultrasound or CT urography, to examine the kidneys and urinary tract
- Considering cystoscopy for direct visualization of the bladder, particularly in adults over 35 years
- Measuring kidney function through blood tests, including creatinine and BUN
- Avoiding screening urinalysis for cancer detection in asymptomatic adults, as recommended by the American College of Physicians 1 It is essential to note that persistent hematuria, even if asymptomatic, should never be ignored, as it may signal serious conditions that require early intervention. Follow-up testing is crucial if the initial evaluation does not reveal a cause but hematuria persists, and clinicians should consider urology referral for cystoscopy and imaging in adults with microscopically confirmed hematuria in the absence of a demonstrable benign cause 1.
From the Research
Definition and Prevalence of Asymptomatic Hematuria
- Asymptomatic hematuria is defined as the presence of three or more red blood cells per high-power field in a properly collected urine specimen without evidence of infection 2, 3.
- The prevalence of microhematuria is 4-5% in routine clinical practice, and it may be due to an underlying disease of the kidneys or the urogenital tract 2.
Causes and Risk Factors of Asymptomatic Hematuria
- The most common causes of microscopic hematuria are urinary tract infection, benign prostatic hyperplasia, and urinary calculi 3.
- Risk factors for urologic malignancy include male sex, age over 35 years, and a history of smoking 3.
- Patients with non-glomerular asymptomatic microhematuria who have risk factors are more likely to have relevant underlying conditions and should undergo augmented, risk-adapted diagnostic evaluation 2.
Diagnostic Evaluation of Asymptomatic Hematuria
- The basic diagnostic evaluation consists of a thorough history and physical examination, measurement of inflammatory parameters and renal function tests, and ultrasonography of the kidneys and bladder 2.
- Patients with persistent or recurrent microhematuria after a negative initial workup may undergo repeat evaluation, including cystoscopy and upper tract imaging 4.
- The yield of repeat evaluation is low, with a detection rate of urologic malignancy of around 1-2% 4.
Management and Treatment of Asymptomatic Hematuria
- Microscopic hematuria in the setting of urinary tract infection should resolve after appropriate antibiotic treatment; persistence of hematuria warrants a diagnostic workup 3.
- Trimethoprim-sulfamethoxazole is a effective combination agent for the treatment of urinary tract infections, with a cure rate of around 85% 5.
- Sulfonamides, nitrofurantoin, and nalidixic acid are also useful for the treatment of uncomplicated lower urinary tract infections 6.