What are the possible causes and next steps if blood is present on a urine dipstick?

Causes of Blood on Urine Dipstick

Blood on a urine dipstick requires thorough evaluation as it may indicate serious underlying conditions including urinary tract malignancy, infection, or kidney disease, with diagnostic approach determined by patient risk factors and associated symptoms.

Common Causes of Hematuria

Urologic Causes

• Urinary tract infection (UTI) - Often accompanied by pyuria, dysuria, frequency, and urgency 1
• Urinary tract malignancy - Bladder cancer, renal cell carcinoma, urothelial carcinoma 1, 2
• Urolithiasis (kidney stones) - Often with flank pain, may have 92.9% sensitivity on dipstick testing 3
• Bladder injuries - Typically associated with trauma, gross hematuria present in 77-100% of cases 1
• Urethral injuries - Often trauma-related, blood at urethral meatus is common 1
• Benign prostatic enlargement - Common in older males 1

Nephrologic Causes

• Glomerular disease - Often accompanied by proteinuria, red cell casts 2
• Medical renal disease - Various forms of nephritis 1

Other Causes

• Exercise-induced hematuria - Typically transient and benign 1
• Medications - Certain drugs like anticoagulants can cause hematuria 2
• Recent urological procedures - Instrumentation can cause temporary bleeding 1
• False positives - Medications (e.g., methylene blue causing blue-green discoloration) 4, myoglobinuria, hemoglobinuria 5

Diagnostic Approach

Initial Assessment

1. Confirm true hematuria:

   • Distinguish between hematuria, hemoglobinuria, and myoglobinuria 5
   • Rule out false positives from medications 4
   • Confirm with microscopic examination (≥3 RBCs per high-power field defines microhematuria) 1

2. Rule out benign causes:

   • Menstruation in women
   • Recent vigorous exercise
   • Recent trauma or procedures
   • Current UTI (confirm with urine culture) 1

Risk Stratification

Categorize patients into risk groups based on:

• Age - Higher risk: women ≥50 years, men ≥40 years 2
• Smoking history - >30 pack-years indicates higher risk 2
• Hematuria intensity - Gross hematuria or >25 RBC/HPF indicates higher risk 2
• Other risk factors - History of pelvic radiation, chronic UTIs, occupational exposures to chemicals/dyes 2

Diagnostic Testing

1. Laboratory evaluation:

   • Complete urinalysis with microscopic examination
   • Urine culture to rule out infection 1
   • Complete blood count to assess for systemic disease 1
   • Renal function tests (BUN, creatinine)
   • Urine cytology for high-risk patients 2

2. Imaging:

   • High-risk patients: CT urography (92% sensitivity, 93% specificity) 2
   • Moderate-risk patients: Consider CT urography or ultrasound based on clinical presentation
   • Low-risk patients or those with contraindications to CT: Renal ultrasound 2

3. Cystoscopy:

   • Recommended for all patients with persistent microscopic hematuria after negative evaluation 2
   • Essential for patients with risk factors for bladder cancer

Management Approach

1. If infection is identified:

   • Treat with appropriate antibiotics
   • Follow-up urinalysis to confirm resolution 1

2. If urolithiasis is diagnosed:

   • Appropriate stone management (medical expulsive therapy, lithotripsy, etc.)

3. If malignancy is suspected:

   • Prompt referral to urology for further management
   • Delays >9 months in evaluation are associated with decreased survival in bladder cancer 2

4. If glomerular disease is suspected (hematuria with proteinuria >1g/day):

   • Referral to nephrology 2
   • Blood pressure control (target ≤125/75 mmHg) 2

5. If initial evaluation is negative:

   • Repeat urinalysis within 2-4 weeks to confirm persistence 2
   • If hematuria resolves, no further testing is needed 6
   • If hematuria persists, consider nephrology referral 6

Follow-up

• Patients with negative initial evaluations who have persistent hematuria should have repeat evaluation in 6-12 months 2
• Patients whose hematuria resolves after negative evaluation can be discharged from urologic care 6
• Immediate reevaluation is necessary if gross hematuria appears or new urologic symptoms develop 2

Common Pitfalls to Avoid

• Assuming benign cause without complete evaluation in high-risk patients 2
• Using inadequate imaging (e.g., ultrasound alone) in high-risk patients 2
• Dismissing microscopic hematuria in patients with overactive bladder symptoms 2
• Delaying referral based on patient sex (avoid sex disparities) 2
• Failing to distinguish between hematuria, hemoglobinuria, and myoglobinuria 5