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This page has been written for patients who are receiving radiotherapy to the prostate. Radiotherapy can sometimes cause temporary and permanent side effects to the rectum (back passage). These side effects are described in the patient information leaflet number 5: “Radiotherapy to the Prostate” and can include injury to the rectum and problems with bowel movements.
Side effects such as pain during bowel movements, soreness or pain in the rectum at other times, rectal urgency (the sensation of needing to have a bowel movement immediately), bleeding or loose stools may also occur during or after radiation treatment. If these side effects happen, they are temporary for most men. But a small number of men have symptoms that persist for years after radiotherapy and may require treatment or, in rare circumstances, surgery to improve the bowel function.
In order to reduce the possibility of these side effects, your Clinical Oncologist or Consultant Urology Radiographer has recommended you consider an additional procedure in which a temporary rectal spacer is implanted between your prostate and rectum before receiving radiotherapy. A rectal spacer is a protective layer of gel that helps reduce the dose of radiotherapy to the rectum. The spacer is often known by the manufacturer’s name SpaceOAR™. OAR is a radiotherapy term that stands for Organ at Risk of side effects, which in this case is the rectum.
Rectal spacers have been carefully tested and are used in radiotherapy centres in the United Kingdom, United States, Europe and elsewhere. Understandably, you will have questions about how and why the procedure is done, and what to expect.
Studies have shown that the use of a rectal spacer is a safe procedure that can reduce rectal side effects after prostate radiotherapy. We hope this page will help to answer many of the questions you may have about the procedure. If you still have any further questions or concerns, please speak to your medical team.
Insertion of a rectal spacer is an optional procedure and should you wish to decline it, your radiotherapy treatment will continue in the same way. You will receive the same dose of radiotherapy, and length of course of radiotherapy as has been discussed with you by your doctor or consultant radiographer.
The goal of radiotherapy treatment is to maximize the radiation dose given to the prostate whilst at the same time avoiding unnecessary radiotherapy to the normal, healthy surrounding tissues.
The prostate gland and the rectum sit next to each other and are separated by only a small space. Due to this closeness, radiotherapy to the prostate means the rectum is inevitably exposed to some radiotherapy dose which can cause side effects.
A rectal spacer is a gel-like substance that temporarily moves the rectal wall away from the prostate by an average of 11mm. By separating the prostate from the rectum, the rectal spacer should reduce the radiotherapy dose to the rectum and consequently reduce side effects to the rectum during and after radiotherapy. This means an individual may experience fewer bowel side effects from the radiotherapy treatment in terms of both early and long-term side effects.
Without a rectal spacer After insertion of a spacer
The rectal spacer is made of two liquids that when combined, form a soft gel-like synthetic material made mostly of water. Because of its water content it is called a hydrogel. The material the rectal spacer is made from is used in implants for other parts of the body, such as the brain and spine. Studies have shown that the material can be used safely in the body.
The procedure is usually done during a separate appointment at University College Hospital before your radiotherapy planning CT scan. If you are having high dose rate brachytherapy, then the procedure will be done on the same day as your brachytherapy treatment.
The rectal spacer is injected through the skin between the scrotum and anus (the perineum). An ultrasound probe is covered in gel and gently placed into the rectum so the radiology doctor can check the gel is being inserted into exactly the correct place in between the prostate and rectum. You may feel a dull pressure as the needle is inserted, you may also feel pressure in the rectum while the ultrasound probe is in place.
This procedure usually takes 30-45 minutes in total, and you should expect to be in the hospital for a further few hours while the anaesthetic wears off.
The medical team will use an anaesthetic to numb the injection area. You may feel a pinprick or pressure but should not feel any major discomfort. After the procedure you may experience some temporary discomfort at the injection site and some men have a feeling of fullness in the rectal area. Patients who have had a rectal spacer inserted typically report no prolonged discomfort from the implanted gel.
You may be given a spinal or local anaesthetic during the procedure. You will not need a full general anaesthetic. The type of anaesthetic used will be discussed with you before you agree to the procedure.
You will have an initial consultation with your clinical oncologist to discuss your radiotherapy treatment. If you choose to have a rectal spacer inserted, you will need to attend a pre-assessment clinic appointment where your overall fitness for the insertion will be assessed. This is routine for any procedure of this kind. You will also be given a prescription for antibiotic tablets. You will need to start taking the course of antibiotics the day before the procedure.
Before you undergo the Spacer insertion procedure you should let the doctor or nurse know of any of the following:
- If you have allergies to any medications, including anaesthetics.
- If you have or have ever had bleeding problems.
- If you have an artificial heart valve.
- If you are taking any medications, particularly antibiotics or anti-coagulants to thin the blood (including aspirin, warfarin and clopidogrel).
If you are taking aspirin, you must stop taking it for seven days before the procedure.
If you are taking warfarin, you will need to stop taking it for five days before the procedure.
If you are on clopidogrel you will need to stop taking it for ten days before the procedure.
Please continue to take all your other medications.
You will need an escort to travel home as you may feel drowsy after the procedure. You should avoid strenuous activities for about four hours. You should also avoid heavy lifting, cycling and core strength gym activity for three days after the procedure. You may experience some mild pain in the rectal area for one to two days after the procedure. If you do, mild painkillers should be adequate to help alleviate any pain.
In order to avoid having to strain your bowels, you should eat plenty of fruit and vegetables and drink one to two litres of fluid a day prior to the procedure. Please avoid alcohol for 24 hours after the procedure. It is advisable not to travel abroad for 72 hours after the procedure and avoid sexual activity for one week after the procedure. This is to help reduce the risk of infection. You will need to take antibiotics for five days to prevent the risk of any infection, even if you feel well.
Every precaution will be taken to minimise any risks from rectal spacer insertion, and you will be given antibiotics before the procedure to reduce the risks of infection.
The procedure will be carried out by an expert who has been specifically trained to insert the rectal spacer.
The potential risks are:
- Infection.
- Slight bleeding.
- Mild discomfort or pain associated with the spacer hydrogel injection.
- Discomfort or pain after insertion due to the rectum being moved slightly forwards.
- Urinary retention requiring the insertion of a catheter.
- Damage to the lining of the rectum, ulcers in the rectum and bleeding from the rectum.
- Rare - needle penetration into the bladder, prostate, rectal wall, rectum, or urethra.
- Rare - injection of spacer hydrogel into bladder, prostate, rectal wall, rectum, urethra or into a blood vessel.
It is very unlikely that you will become unwell following the procedure. However, if you experience any of the following symptoms at home, please go to your local accident and emergency. Please tell the staff that they must contact UCLH and ask the operator to bleep the on-call Oncology Specialist Registrar.
The number for UCLH is: 020 3456 7890 or 0845 155 5000.
- Your pain increases.
- You feel unwell or shivery.
- You have a fever higher than 38°C (100.4°F).
- You are unable to urinate within eight hours.
- You start to pass large clots of blood.
- You have persistent bleeding.
Clinical trials have shown rectal spacers do not move during treatment once the gel has set.
If you choose not to have a rectal spacer inserted, you will receive the same radiotherapy treatment as discussed with your clinical oncologist or consultant radiographer.
We hope you have found this leaflet helpful. If you have any questions or other worries and would like to speak to someone, please ask a member of staff.
Macmillan Information and Support Radiographer
Paula Treasure
Direct telephone: 020 3447 3711
Main switchboard: 020 3456 7890, ext 73711/bleep 1458
Email: p.
If you have any concerns that you would like to discuss in confidence, please contact our PALS (Patient Advice and Liaison Service) for information and advice. Email: PALS@uclh.nhs.uk
Telephone: 020 3447 3042
Website: www.
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Page last updated: 18 June 2024
Review due: 01 June 2026