Patient preparation Warfarin anticoagulant therapy is stopped 3 days before biopsy procedure and biopsy is not performed if international normalized ratio (INR) value is over 2,0. If needed, low molecular weight heparin can be administered to the patient. A cleansing enema is not strictly required. One hour before the biopsy procedure is planned a peroral antibiotic (Trimethoprim 160 mg, Sulfamethoxazole 800 mg) is administered and additional dose is taken the following evening.