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

Urologic Causes of Hematuria

• Malignancy: Accounts for 30-40% of gross hematuria cases and 2.6-4% of microscopic hematuria cases 2

  • Bladder cancer, kidney cancer, and prostate cancer are common urologic malignancies presenting with hematuria 1
  • Risk factors include male gender, age >35 years, smoking, occupational exposure to chemicals, analgesic abuse, history of urologic disease, irritative voiding symptoms, history of pelvic irradiation, chronic UTI, exposure to carcinogens/chemotherapy, and chronic indwelling foreign bodies 2

• Urinary Tract Infection: Common cause of both microscopic and macroscopic hematuria 1, 3

• Urolithiasis (Kidney and Ureteric Stones): Often causes painful hematuria 1, 4

• Benign Prostatic Hyperplasia (BPH): Common benign cause of hematuria in men 2, 5

• Trauma: Injury to kidneys or lower urinary tract can cause hematuria 1

Renal/Glomerular Causes of Hematuria

• Glomerulonephritis: Including post-infectious and IgA nephropathy 1

  • Tea-colored urine suggests a glomerular source of hematuria 1

• Renal Parenchymal Disease: Most common benign nephrogenic cause of hematuria 2

• Alport Syndrome: Hereditary nephritis with associated hearing loss 1

• Other Nephropathies: Such as lupus nephritis and vasculitis 1

Systemic/Other Causes of Hematuria

• Vigorous Exercise: Can cause transient hematuria 1, 2

• Menstruation: Can cause contamination of urine samples in women, leading to false-positive results 1, 2

• Medications:

  • Anticoagulants and antiplatelet agents may unmask underlying pathology but do not directly cause hematuria 1, 5
  • Anticoagulation therapy is not a reason to forgo evaluation of hematuria 1

• Coagulopathies: Such as hemophilia can cause hematuria due to bleeding disorders 1

• Sickle Cell Disease: Can cause hematuria due to renal papillary necrosis 1

• Endometriosis: Can involve the bladder and cause urinary symptoms including hematuria 6

Age-Specific Considerations

• Children: Glomerulonephritis and congenital anomalies are common causes 1

• Adults: Malignancy risk increases significantly in those over 35 years old 1

Important Clinical Considerations

• Gross hematuria has a high association with malignancy (30-40%) and requires urgent urologic referral, even if self-limited 2, 1, 7

• In most patients with asymptomatic microscopic hematuria, a cause is never found 2

• Patients without risk factors and with an identified benign cause of microhematuria (exercise, infection, trauma, menstruation, recent urologic procedure) may not require extensive imaging workup 2

• Dipstick positivity should be confirmed with microscopic analysis showing ≥3 RBCs per high-power field before initiating workup 1, 2

• Anticoagulation therapy may exacerbate bleeding from existing lesions but is not typically the primary cause of hematuria 5

• Patients with suspected urinary tract infection should have urine cultures performed, preferably before antibiotic therapy 2