This booklet explains more about the insertion of a rectal spacer for radiotherapy, including the benefits, risks and any alternatives. It also provides information on what you can expect when you come to hospital.

If you have any further questions, please speak to your cancer doctor, nurse or radiographer caring for you.

A rectal spacer is a water-based gel that is inserted into the space between the prostate and rectum (which is the lower part of your bowel). The spacer moves the rectum away from the prostate and helps to reduce radiotherapy side effects to the rectum.

The goal of radiotherapy to the prostate is to maximise the radiation dose to the prostate to kill the cancer cells while avoiding irradiating surrounding normal tissue.

The rectum sits close to the prostate, so it can receive a high radiation dose which can lead to side effects. The spacer is inserted between the prostate and rectum, therefore it pushes the rectum away from the prostate and away from the high radiation dose, reducing the risk of side effects. 

The spacer will be inserted whilst you are asleep under a general anaesthetic. This may take place as part of another procedure such as fiducial marker insertion, if you require these. If you have this procedure you will receive an information leaflet about the fiducial markers also. 

You will be given an enema to empty your rectum shortly before the procedure. The rectal spacer insertion takes about 30 minutes. Once you are anaesthetised, the doctor will inject the spacer as a liquid through a small needle between the rectum and the prostate. The needle is inserted through the skin behind your scrotum (the perineum). The doctor will use ultrasound imaging to make sure it is in the correct place. Once inside the body, the spacer forms a firm gel and will remain in place during your treatment, gradually biodegrading three to six months after insertion.

Will I feel any pain?

There is not usually much pain from this procedure, although you may be a little sore. We can give you painkillers if you need them, so please let us know if you are in pain. We will usually give you oral painkillers such as paracetamol or ibuprofen, which you can take as soon as you are able to eat and drink.

The spacer is made of a synthetic material mostly consisting of water. Many studies have shown that the material is biocompatible and can be used safely in the body. The use of rectal spacers is approved by the National Institute for Health and Care Excellence (NICE) under special arrangements.

Read more about NICE guidance on Spacers:

There is a very small risk, less than one in 100 (1%), of complications from the spacer if it is inserted incorrectly into a vessel or into the rectum. If this were to happen, you would have to wait for three months for the gel to be absorbed into your body before repeating the procedure. This may delay the radiotherapy treatment.

Modern anaesthesia is very safe and serious problems are uncommon. Your anaesthetist (a doctor who gives anaesthetics) will monitor you closely throughout the procedure. However, risk cannot be removed completely and some people may have side effects or complications. 

The insertion is a fairly safe procedure and is performed by experienced doctors.

If there is a lot of scarring around the lower bowel (for example from several trans-rectal prostate biopsies, anal fistulas, infections or surgery) it might not be possible to get the spacer in the right position. This is normally not a problem as the hydrogel is reabsorbed, but it may be less effective. Some side effects are as follows: infection, bleeding, mild discomfort/pain, urinary retention, damage to the rectum lining - but these are uncommon.

The needle used for the insertion can penetrate other organs and may cause some organ damage, but this risk is very rare. 

You can have radiotherapy without a spacer. Your radiotherapy treatment will be carefully planned to reduce the dose to your rectum which will minimise the risk of side effects.

We want to involve you in decisions about your care and treatment. If you decide to go ahead, you will be asked to sign a consent form. This states that you agree to have the treatment, that you understand what it involves and that you are aware of any risks. If you would like more information about our consent process, please speak to a member of staff caring for you.

Pre-assessment clinic
You will need to come to a pre-admission clinic before you have the spacer inserted. We will check your suitability for general anaesthetic at this appointment. A general anaesthetic is where you are put to sleep. This will be discussed with you in more detail at your clinic appointment. We will carry out a number of tests to make sure that your heart, lungs and kidneys are working properly. You may have a chest X-ray, electrocardiogram (ECG – a recording of the electrical activity of your heart) and some blood taken. Your cancer doctor will explain any further tests you need.

Please let us know if you are taking any antiplatelet medicines (for example, aspirin, clopidogrel), any medicines that thin the blood (for example, warfarin, apixaban or rivaroxaban), or anti-inflammatory painkillers (for example Ibuprofen or Naproxen); these may need to be stopped temporarily before the procedure. Also tell us if you have diabetes, as you may need to alter the dose of your diabetes medicines, as you will need to fast before the procedure. We will give you more advice about this. 

Do not make any changes to your usual medicines, and continue to take them, unless you are told otherwise. Please remember to bring them with you to the pre-admission clinic and on the day of your procedure. Please let us know if you are taking any regular medicines (including anything you buy over the counter and any herbal or homeopathic medicines) and if you have any allergies to any medicines.

Fasting instructions
Please do not eat for six hours before your anaesthetic procedure. You are allowed to sip water up to two hours before your appointment. Do not suck on sweets or chew gum. This will be explained to you in the pre-admission clinic. If you do not follow these instructions, your procedure will be cancelled.

If you smoke, you may be asked to stop smoking, as this increases the risk of developing a chest infection or deep vein thrombosis (DVT – a blood clot developing in a deep vein). Smoking can also delay wound healing because it reduces the amount of oxygen that reaches the tissues in your body. If you would like to give up smoking, please speak to your GP or call the NHS Smoking Helpline, t: 0800 022 4322

Following the procedure you will be taken to the recovery room. You will stay there until you wake up from the anaesthetic, which usually takes about an hour. After this, you will be taken back to your ward or day unit.

When you wake up you may have a drip (a bag of fluid connected to a small tube in a vein in your arm) to keep you well hydrated until you are able to drink fluids.

Passing urine may be a little uncomfortable at first. If you have problems with this you may need a catheter inserted, although most patients do not need this. When you have a general anaesthetic you will need a relative or friend to accompany you home afterwards, and to be with you for the next 24 hours. You cannot drive on the day of your procedure. 

You will be given a course of antibiotics to start on the evening of your insertion. You must complete the course as it will reduce the risk of urinary infection. When you go home, please drink plenty of clear fluids each day. We recommend two-three litres of water, and limit any caffeine (tea or coffee), fizzy drinks and alcohol. You should be able to return to normal activities within about three days.

Will I have a follow-up appointment?
You will be given an appointment to attend for a CT scan for your radiotherapy planning. Some patients may require an MRI scan too but you will be informed of this is you need one. If you have HDR brachytherapy you will have an appointment for this one-two weeks later. The appointment will be sent to you in the post.

Please speak to the Radiographers if you have further questions.