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
• Microscopic Hematuria: Blood in urine only detectable under microscope (≥3 red blood cells per high-power field) 1, 2

Urologic Causes

• Malignancy: Accounts for 30-40% of gross hematuria cases and 2.6-4% of microscopic hematuria cases, including bladder cancer, kidney cancer, and prostate cancer 1, 3
  • Risk factors include male gender, age >35 years, smoking, and occupational exposure to chemicals 1
• Urinary Tract Infection: Common cause of both microscopic and macroscopic hematuria 1, 4
• Urolithiasis: Kidney and ureteric stones can cause painful hematuria 1, 4
• Benign Prostatic Hyperplasia (BPH): Common benign cause of hematuria in men 1, 3
• Trauma: Injury to the kidneys or lower urinary tract can cause hematuria 1

Renal/Glomerular Causes

• Glomerulonephritis: Including post-infectious and IgA nephropathy 1, 5
• Alport Syndrome: Hereditary nephritis with associated hearing loss 1, 5
• Other Nephropathies: Such as lupus nephritis and vasculitis 1, 5
• Thin Basement Membrane Nephropathy: Autosomal dominant condition, reported to be a common cause of progressive chronic kidney disease 5
• Interstitial Renal Disease: Including drug-induced interstitial disease or analgesic nephropathy 5

Systemic/Other Causes

• Vigorous Exercise: Can cause transient hematuria 1, 6
• Menstruation: Can cause contamination of urine samples in women, leading to false-positive results 1, 6
• Medications: Anticoagulants and antiplatelet agents may unmask underlying pathology but do not cause hematuria themselves 1, 3
• Coagulopathies: Such as hemophilia can cause hematuria due to bleeding disorders 1
• Sickle Cell Disease: Can cause hematuria due to renal papillary necrosis 1

Age-Specific Considerations

• In children: Glomerulonephritis and congenital anomalies are common causes of hematuria 1, 7
• In adults: Malignancy risk increases, especially in those over 35 years old 1, 3

Diagnostic Approach Based on Type of Hematuria

For Gross Hematuria:

• Requires urgent urologic referral due to high association with malignancy (30-40%), even if self-limited 1, 8
• Complete urologic evaluation including imaging and cystoscopy 5, 8

For Microscopic Hematuria:

• Determine if glomerular or non-glomerular in origin by examining urinary sediment for dysmorphic RBCs 5
• Glomerular bleeding is associated with >80% dysmorphic red blood cells 5
• Lower urinary tract bleeding is associated with >80% normal red blood cells 5
• Check for proteinuria - significant proteinuria suggests renal parenchymal disease 5

Important Clinical Considerations

• Tea-colored urine suggests a glomerular source of hematuria 1
• Dipstick positivity should be confirmed with microscopic analysis showing ≥3 RBCs per high-power field before initiating workup 1, 2
• Patients with persistent hematuria after negative initial evaluation require follow-up at 6,12,24, and 36 months 3
• Consider nephrology referral if hematuria persists with development of hypertension, proteinuria, or evidence of glomerular bleeding 3, 5
• Anticoagulation therapy is not a reason to forgo evaluation of hematuria 1, 3