How long should heparin (unfractionated heparin) be held before a kidney biopsy?

Unfractionated Heparin Hold Time Before Kidney Biopsy

Unfractionated heparin (UFH) should be discontinued 4-6 hours before a kidney biopsy to completely eliminate its anticoagulant effect. 1

Pharmacokinetic Rationale

• UFH has a half-life of approximately 60-90 minutes, though this can vary between 30-120 minutes depending on the level of anticoagulation at the time of discontinuation 1, 2
• The 4-6 hour interval allows the anticoagulant effect to be completely eliminated before the procedure 1
• In patients with pulmonary embolism, heparin half-life may be significantly shortened, but the 4-6 hour window remains adequate 2

Kidney Biopsy-Specific Bleeding Risk

• Percutaneous kidney biopsy carries a major bleeding complication rate of approximately 6-7%, requiring transfusion or invasive intervention 3, 4
• Major complications occur in up to 6.6% of cases, with over 90% becoming apparent within 24 hours post-biopsy 3, 4
• The risk of life-threatening complications is less than 0.1% in recent series 3

Critical Timing Considerations

• For intravenous UFH infusion: Stop the infusion 4-6 hours before the biopsy 1
• For subcutaneous UFH: The last dose should be given at least 12 hours before the procedure, as subcutaneous absorption creates a longer duration of effect 5
• No bolus dose should be given within 4-6 hours of the procedure 1

Post-Biopsy Resumption

• UFH can be restarted without a bolus more than 4 hours after the procedure, once hemostasis is confirmed 1
• For kidney biopsy specifically, waiting 12-24 hours is prudent given the high vascularity of the kidney and delayed bleeding risk 5, 4
• Start with a lower-intensity infusion without bolus dosing to minimize bleeding risk 1

Common Pitfalls to Avoid

• Do not rely on bleeding time as a screening test before kidney biopsy—it is not significantly predictive of post-biopsy bleeding complications 6, 3
• Do not assume 4 hours is sufficient for subcutaneous UFH—the absorption kinetics require a longer hold time of at least 12 hours 5
• Do not restart UFH too early—the majority of major bleeding complications from kidney biopsy occur within the first 12-24 hours 4