Transrectal ultrasound-guided prostate puncture biopsy is usually performed in the ultrasound room. You should stop taking anticoagulants such as aspirin and warfarin for at least 2 weeks prior to this test (if you have had previous heart valve replacement surgery, you should give your urologist instructions and determine when to stop or how to reduce the dosage), as bleeding is likely to occur if you do not stop. Because the rectum is the most terminal part of the gastrointestinal tract and contains a large number of gram-negative bacteria, you will need to have an enema to cleanse your rectum and intravenous antibiotics to prevent infection prior to this test. For this test, the doctor usually has you lie on your left side with your legs tucked in. The ultrasound probe is placed into your rectum, which is slightly uncomfortable, and a puncture biopsy of the prostate is performed under ultrasound monitoring. There is a slight pain during the puncture, which is generally tolerated by people.