What to do with a patient on warfarin (anticoagulant) with a mechanical heart valve and therapeutic PT/INR (prothrombin time/international normalized ratio) levels who presents with microscopic hematuria (blood in urine)?

Management of Microscopic Hematuria in a Patient on Warfarin with a Mechanical Heart Valve

Patients on warfarin with microscopic hematuria should undergo a complete urologic evaluation regardless of their anticoagulation status, as hematuria often indicates significant underlying pathology even when anticoagulants are present. 1, 2

Initial Assessment

• Evaluate the INR to confirm it remains in therapeutic range (2.5-3.5 for mechanical mitral valves) 3, 4
• Microscopic hematuria in patients on anticoagulation requires thorough investigation as it frequently reveals significant urologic pathology 1, 5
• The presence of blood in urine (200 initially, now 25) with trace occult blood suggests ongoing microscopic hematuria that requires evaluation 6

Management Algorithm

Step 1: Maintain Anticoagulation

• Do not discontinue warfarin therapy as the risk of valve thrombosis outweighs the risk of continued microscopic hematuria in a patient with a mechanical heart valve 3
• Continue monitoring INR regularly to ensure it remains in therapeutic range (2.5-3.5) 4

Step 2: Urologic Evaluation

• Refer for complete urologic evaluation including: 1, 5
  • Urinalysis with microscopy to confirm RBC morphology and presence of casts 7
  • Urine culture to rule out infection 6
  • Renal function tests to assess for acute kidney injury 7
  • Upper tract imaging (ultrasound or CT urography) 5
  • Cystoscopy to evaluate the bladder and urethra 2, 5

Step 3: Consider Temporary Adjustment of Anticoagulation

• If extensive urologic procedures are needed, consider temporary adjustment of anticoagulation: 3
  • For high-risk patients with mechanical mitral valves, use bridging therapy with intravenous unfractionated heparin when INR falls below 2.0 3
  • Stop heparin 4-6 hours before procedure and restart as soon as hemostasis is achieved 3

Special Considerations

• Bleeding that occurs at an INR of 3.0 is frequently associated with an underlying lesion in the urinary tract 3
• Microscopic hematuria in anticoagulated patients may indicate significant pathology including malignancy, which has >10% risk with gross hematuria 6, 2
• Warfarin-related nephropathy can occur, presenting with glomerular hemorrhage and acute kidney injury, especially in patients with pre-existing kidney disease 7

Potential Pitfalls

• Do not assume hematuria is solely due to anticoagulation - studies show significant pathology is found in most anticoagulated patients with hematuria 1, 2
• Do not discontinue warfarin without a bridging plan in patients with mechanical heart valves due to high risk of thromboembolism 3
• Avoid high-dose vitamin K for reversal as this may create a hypercoagulable condition 3, 8
• Do not delay urologic evaluation as early detection of malignancy allows for more effective treatment 2

Follow-up

• After initial evaluation, follow up on all test results and specialist consultations 6
• If no significant pathology is found but hematuria persists, consider periodic reassessment every 3-6 months 5
• If a benign cause is identified, treat accordingly while maintaining anticoagulation 3