A transrectal ultrasound-guided prostate biopsy is a medical procedure that uses an ultrasound probe inserted into the rectum to visualize the prostate and guide a thin needle to obtain small tissue samples. The primary purpose is to test these samples for prostate cancer, serving as a common and direct diagnostic method when initial screenings suggest a concern.
Indications for a Biopsy
A doctor recommends a prostate biopsy when initial screening tests suggest prostate cancer. One indicator is an elevated or rapidly rising Prostate-Specific Antigen (PSA) level in a blood test. PSA is a protein produced by prostate cells; cancerous cells often lead to higher levels. However, elevated PSA alone does not confirm cancer, as other factors like an enlarged prostate, inflammation, or urinary tract infections can also cause levels to rise.
Another reason for a biopsy is an abnormal finding during a Digital Rectal Exam (DRE). During a DRE, a doctor manually checks the prostate through the rectum for unusual size, shape, or texture. While DREs and PSA tests identify individuals who might have prostate cancer, a biopsy is the definitive procedure to confirm a diagnosis.
The Biopsy Procedure
Preparation
Prior to a transrectal prostate biopsy, patients receive specific instructions to minimize risks. Patients are advised to stop taking medications that increase bleeding, such as aspirin, ibuprofen, or blood thinners, 7 to 10 days beforehand. Patients take prescribed prophylactic antibiotics, starting one to two days before, to reduce infection risk. An over-the-counter enema is often required a few hours before the appointment to clear the rectum.
During the Procedure
The biopsy is performed in an outpatient setting, lasting between 15 to 30 minutes. The patient is positioned on their side with knees pulled up towards the chest, or on their stomach. A thin, lubricated ultrasound probe is gently inserted into the rectum to generate real-time images of the prostate gland.
Using these ultrasound images as a guide, a local anesthetic, such as lidocaine, is injected to numb the areas from which samples will be taken. Patients may feel some pressure from the probe and a brief stinging sensation from the anesthetic injection. Multiple tissue samples, called “cores,” are then collected using a spring-loaded biopsy instrument that makes a distinct clicking sound. Ten to twelve samples are taken from different regions of the prostate.
Immediately After
Immediately following sample collection, the ultrasound probe is removed. Patients are observed for a short period to ensure no immediate complications. Light activities are recommended for the first 24 to 48 hours, and patients are advised to continue taking their prescribed antibiotics for a few days.
Risks and Side Effects
After a transrectal prostate biopsy, several common side effects generally resolve without extensive intervention. Patients experience minor rectal bleeding, appearing as spotting or streaks in stool for a few days. Blood in the urine (hematuria) is also common, presenting as a pink or reddish tint that can last from 12 hours up to three weeks. Blood in the semen (hematospermia) is a common side effect, causing semen to appear red or rust-colored, and can persist for several weeks to months. Mild discomfort or soreness in the rectal area or at the base of the penis is also expected for a few days.
More serious risks, though less common, warrant careful attention. Infection is a primary concern, with rates ranging from 1.7% to 6%. This can occur if bacteria from the rectum are introduced into the prostate or bloodstream during the procedure. To mitigate this, completing the full course of prescribed antibiotics is important. Signs of a serious infection, such as fever (over 100.5°F or 38.1°C), chills, persistent burning with urination, or worsening pain, require immediate medical attention. Urinary retention, where a patient is unable to urinate, occurs in about 0.4% to 6% of procedures and may necessitate a temporary urinary catheter. This is more common in older men or those with larger prostates.
Understanding the Results
Once tissue samples are collected, they are sent to a pathology lab for analysis. A pathologist, a doctor specializing in diagnosing diseases by examining tissues, studies the samples under a microscope to determine if cancer cells are present. If cancer is detected, the pathologist assigns a Gleason Score, a system used to grade the aggressiveness of the prostate cancer.
The Gleason Score is determined by examining how much the cancer cells resemble healthy prostate cells. Cells similar to normal cells are low-grade (e.g., Grade 1), while very abnormal cells are high-grade (e.g., Grade 5). Since prostate cancers often contain cells of different grades, the pathologist identifies the two most common grades in the biopsy sample and adds them to produce the Gleason Score. Scores range from 6 to 10, with a score of 6 indicating a slower-growing cancer and higher scores (e.g., 8-10) suggesting a more aggressive one.
A “benign” or “negative” result means no cancer cells were found. If the result is malignant, the urologist will discuss the specific Gleason Score and its implications. This discussion includes considering the cancer’s aggressiveness, location, and spread within the prostate. Based on these findings, the doctor will outline potential next steps, ranging from active surveillance (close monitoring) for slow-growing cancers to various treatment options if the cancer is more aggressive.