What are the causes of hematuria (blood in the urine)?

Causes of Hematuria

Hematuria can be caused by a wide range of conditions affecting the urinary tract, with potential etiologies ranging from benign causes to malignant conditions that require urgent evaluation and treatment. 1

Classification of Hematuria

• Macroscopic (Gross) Hematuria: Visible blood in urine that can be seen with the naked eye 1, 2
• Microscopic Hematuria: Blood in urine only detectable under microscope (≥3 red blood cells per high-power field) 3, 4

Common Causes of Hematuria

Urologic Causes

• Malignancy: Bladder cancer (most common urologic malignancy causing hematuria), kidney cancer, prostate cancer 1, 2
  • Risk of malignancy with gross hematuria is 30-40% 5, 6
  • Risk of malignancy with microscopic hematuria is 2.6-4% 3, 7
• Urinary Tract Infection: Common cause of both microscopic and macroscopic hematuria 1, 6
• Urolithiasis: Kidney and ureteric stones can cause painful hematuria 1, 8
• Benign Prostatic Hyperplasia: Can cause microscopic hematuria due to increased vascularity 6
• Trauma: Injury to kidneys or lower urinary tract 1
• Recent Urologic Procedures: Catheterization, cystoscopy, or surgery 3

Renal/Glomerular Causes

• Glomerulonephritis: Various forms including post-infectious, IgA nephropathy (Berger disease) 1, 4
• Alport Syndrome: Hereditary nephritis with associated hearing loss 1
• Thin Basement Membrane Disease: Common cause of isolated glomerular hematuria 4
• Other Nephropathies: Lupus nephritis, vasculitis 1

Systemic/Other Causes

• Vigorous Exercise: Can cause transient hematuria 3
• Menstruation: Can cause contamination of urine samples in women 3
• Medications: Anticoagulants and antiplatelet agents (do not cause hematuria but may unmask underlying pathology) 1, 5
• Coagulopathies: Bleeding disorders such as hemophilia 1
• Sickle Cell Disease: Can cause hematuria due to renal papillary necrosis 1
• Endometriosis: Bladder involvement can cause hematuria 5
• Factitious Causes: Food substances or medications that color urine without actual presence of blood 1

Age-Specific Considerations

In Children

• Glomerulonephritis: Post-infectious, Henoch-Schönlein purpura 1
• Congenital Anomalies: More common cause in pediatric population 1
• Hypercalciuria: Important cause of isolated hematuria in children 1

In Adults

• Malignancy: Risk increases with age (>35 years) 3, 2
• Urolithiasis: Common in middle-aged adults 8
• Benign Prostatic Hyperplasia: Common in older men 6

Risk Factors for Urologic Malignancy

• Age >35 years: Increased risk with advancing age 3
• Smoking history: Significant risk factor for bladder cancer 3
• Occupational exposures: Chemical exposures increase risk 3
• Male gender: Higher risk compared to females 7
• Gross hematuria: Stronger association with malignancy than microscopic hematuria 5, 6
• Persistent hematuria: Requires thorough evaluation 1

Clinical Pearls and Pitfalls

• Never ignore gross hematuria: All cases require urologic referral, even if self-limited 1, 5
• Anticoagulation therapy: Not a reason to forgo evaluation of hematuria 1
• "Idiopathic microscopic hematuria": Accounts for approximately 80% of asymptomatic cases after complete evaluation 7
• Tea-colored urine: Suggests glomerular source of hematuria 1
• Contamination: Menstrual blood can produce false-positive results for hematuria; catheterized specimen may be needed 3
• Dipstick positivity: Should be confirmed with microscopic analysis showing ≥3 RBCs per high-power field before initiating workup 1, 3