The SpaceOAR hydrogel placement procedure takes about 30 minutes, though you’ll typically spend around 60 minutes total at the clinic when you factor in preparation, setup, and a brief observation period afterward. Some facilities use general anesthesia, which adds more time for pre-procedure checks and post-procedure recovery in a care unit.
What Happens During the 30 Minutes
The actual injection is straightforward. You lie on your back with your legs supported, and the doctor uses an ultrasound probe to guide the placement in real time. A needle is inserted through the skin between the scrotum and rectum (the perineum), and the hydrogel is injected into the small space between the prostate and the rectum. Only a single skin puncture is needed for the gel alone. If your doctor is also placing fiducial markers (tiny metal seeds that help target radiation), three separate puncture sites are used, and the markers go in first.
The gel works by pushing the rectal wall about 1 to 1.5 centimeters away from the prostate, creating a buffer zone that shields the rectum during radiation therapy. It’s placed correctly about 99% of the time.
Local vs. General Anesthesia
How long your visit takes depends partly on which type of anesthesia your facility uses. Many radiation oncology clinics perform the procedure under local anesthesia, numbing the perineal area and the deeper tissue near the prostate with lidocaine. This keeps the total visit closer to that 60-minute window.
Some hospitals, including major cancer centers like Memorial Sloan Kettering, use general anesthesia instead, meaning you’ll be fully asleep. In that case, expect a longer visit. You’ll need an IV placed beforehand, and afterward you’ll wake up in a recovery unit where staff monitor you before discharge. Plan for several hours at the facility if general anesthesia is involved.
Preparation Before the Procedure
The prep starts the day before. You’ll typically give yourself a saline enema the evening before and another one a few hours before your appointment to clear the rectum so the ultrasound gives a clear image. Your doctor may also prescribe an antibiotic to take beforehand to reduce infection risk.
If you’re receiving general anesthesia, you’ll need to stop eating by midnight the night before. Clear liquids like water, black coffee, or apple juice are allowed up until two hours before your arrival time. Let your care team know if you take blood thinners, steroids, or GLP-1 medications (used for diabetes or weight loss), since these can require adjustments to the standard prep instructions.
Recovery and Getting Back to Normal
Recovery is quick for most people. With local anesthesia, you can generally leave the clinic shortly after the procedure. With general anesthesia, you’ll spend time in a post-anesthesia care unit until the sedation wears off, but you’ll still go home the same day. Most men return to normal activities within a day or two. You may notice mild soreness or swelling at the injection site, but significant pain is uncommon.
Radiation therapy typically begins within a few weeks of placement. The hydrogel is designed to remain stable for three to six months before gradually breaking down and being absorbed by the body, giving it plenty of time to serve its protective role through a full course of radiation. In some cases, the gel persists longer than six months, but this doesn’t cause problems for most patients.
Why It’s Worth the Time
The 30 minutes spent placing SpaceOAR translates to meaningful protection during radiation. A systematic review found the hydrogel significantly reduces the radiation dose reaching the rectum, regardless of which type of radiation therapy is used. The clinical payoff: late gastrointestinal side effects dropped from 6% to 1% in patients who had the spacer placed. That means less rectal irritation, less bleeding, and fewer long-term bowel problems after treatment.
Risks to Know About
Complications are rare, occurring in roughly 9 out of every 1,000 cases. When problems do happen, they can include the gel ending up in the wrong location, penetrating the rectal wall, or, very rarely, causing an abscess near the prostate. About half of patients who experience a complication have noticeable symptoms, while the other half have misplacements detected only on imaging. A misplaced spacer can sometimes delay the start of radiation or, in uncommon cases, fail to provide the intended protection. Your doctor should discuss these possibilities before the procedure, but the overall track record is strong.