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

From the Guidelines

Microscopic haematuria is primarily caused by benign conditions such as urinary tract infections, kidney stones, and benign prostatic hyperplasia, but can also be a sign of more serious conditions like urological malignancies, particularly in patients over 35 years old. The causes of microscopic haematuria can be divided into nephrogenic and urogenic causes, with renal parenchymal disease being the most common benign nephrogenic cause 1. Common benign urogenic causes include urolithiasis, infection, and benign prostatic hypertrophy 1. Malignant causes can occur anywhere in the urinary tract and are the main entity that must be excluded during the imaging evaluation of hematuria.

Key Causes of Microscopic Haematuria

• Urinary tract infections
• Kidney stones
• Benign prostatic hyperplasia
• Glomerular diseases
• Urological malignancies (bladder, kidney, prostate cancer)
• Trauma to the urinary tract
• Polycystic kidney disease
• Medications such as anticoagulants, aspirin, and certain antibiotics
• Exercise-induced haematuria
• Systemic conditions like sickle cell disease, endocarditis, and vasculitis

Evaluation and Diagnosis

Proper evaluation typically includes urinalysis, imaging studies, and sometimes cystoscopy to determine the underlying cause, especially in patients over 40 years old where malignancy risk increases 1. The American Urological Association recommends that all patients 35 years or older should undergo cystoscopy, and upper urinary tract imaging is indicated in all adults with microscopic haematuria in the absence of known benign causation 1. It is essential to note that the risk of malignancy in patients with microscopic haematuria is low, ranging from 2.6% to 4%, but increases with age and the presence of other risk factors 1.

From the Research

Microscopic Haematuria Causes

• Microscopic haematuria can be an indicator of various underlying conditions, including:
  • Infection
  • Kidney stones
  • Trauma
  • Exercise
  • Spurious causes, such as foods, drugs, or menstruation
  • Urological tumours, including bladder cancer, upper tract urothelial carcinoma, and kidney cancer 2, 3
• The likelihood of a urological cancer in patients with microscopic haematuria increases with age, male sex, and cigarette smoking 3
• Approximately 20% of patients with haematuria have a urological tumour, with a further 20% found to have a significant underlying pathology 2
• Cancer detection rates in individuals evaluated for microscopic haematuria range from:
  • 0% to 16% for bladder cancer
  • 0% to 3.5% for upper tract urothelial carcinoma
  • 0% to 9.7% for kidney cancer 3

Risk Factors and Evaluation

• Individuals with dipstick positive haematuria aged ≥40 years, who have had potential precipitating causes excluded, should undergo an evaluation 3
• Re-evaluation of patients with unremarkable initial investigations should be performed in high-risk patients or if new symptoms occur 3