Radiation proctitis and cystitis: late effects of pelvic radiotherapy

Pelvic radiotherapy treats cancers in the lower abdomen and pelvis. Short-term bowel and bladder side effects often settle within a few weeks. For some people, symptoms continue or appear much later, because radiation has changed the lining of the rectum or bladder. These late effects are called radiation proctitis and radiation cystitis. This guide explains the symptoms, when to seek help, the usual treatments, and what trials of hyperbaric oxygen have and have not shown.

What are radiation proctitis and radiation cystitis?

Macmillan Cancer Support explains that radiotherapy can damage the lining of the bowel. As it heals, new small blood vessels form on the surface, and these can break and bleed. The same process in the bladder lining causes radiation cystitis, with pain or burning when passing urine and sometimes blood in the urine.

Both are late effects, meaning they can persist after treatment or first appear months, or even years, after treatment finishes. A clinical review on NCBI StatPearls describes chronic radiation proctitis appearing 6 months to several years after radiation, and a companion review on radiation cystitis reports an average of about 32 months before symptoms start.

What symptoms should you look out for?

Macmillan lists these late bowel effects:

• bleeding from the rectum (back passage)
• passing mucus from the rectum
• diarrhoea or constipation
• difficulty emptying the bowel completely
• urgency, needing to go at night, or bowel incontinence

And these late bladder effects:

• needing to pass urine more often (frequency)
• being unable to wait (urgency)
• leaking urine
• a burning feeling when passing urine
• blood in the urine
• difficulty passing urine

When should you contact your GP or cancer team?

Do not assume a symptom is "just the radiotherapy". Macmillan advises telling your doctor or specialist nurse about any bleeding from the rectum, even if you think you know the cause, and reporting side effects that do not go away or new problems after treatment has ended.

The NHS gives clear thresholds:

• Blood in your urine: ask for an urgent GP appointment or contact NHS 111, even if you have no other symptoms.
• Black or dark red poo, or bloody diarrhoea: ask for an urgent GP appointment or contact NHS 111.
• Bleeding that will not stop, or a lot of blood (the toilet water turns red or you see large clots): go to A&E or call 999.
• Difficulty passing urine: see your doctor promptly.

How are they usually treated?

Your team will usually want to look first. For bowel symptoms that may mean a sigmoidoscopy or colonoscopy, a thin camera passed into the bowel. Macmillan notes that specialist help can come from gastroenterologists, colorectal surgeons, urologists, gynaecologists, continence advisers and physiotherapists, and some hospitals run dedicated late effects clinics.

For radiation proctitis, Macmillan lists:

• sucralfate, given as a liquid into the rectum to coat and protect the lining
• argon plasma coagulation, which uses heat to treat the bleeding areas
• formalin applied to seal bleeding vessels
• hyperbaric oxygen therapy

StatPearls describes sucralfate enemas as the preferred first-line option, with other medicines, antibiotics and endoscopic treatments also used.

For radiation cystitis, the StatPearls review describes medicines for frequency and urgency, bladder irrigation as first-line treatment, agents placed into the bladder, hyperbaric oxygen, and surgery for persistent complications, which carries significant risk.

What does the evidence say about hyperbaric oxygen?

Hyperbaric oxygen means breathing high-concentration oxygen in a pressurised chamber. The idea is that extra oxygen may help damaged tissue grow healthier blood vessels. The trials are genuinely mixed, so each is worth reading with its design, size, pressure and dose.

Clarke, 2008 (proctitis). A randomised, double-blind, sham-controlled crossover trial entered 150 people with radiation proctitis that had not responded to other treatment, of whom 120 could be evaluated. The active group breathed oxygen at 2.0 ATA and the sham group breathed air at 1.1 ATA; the Cochrane review notes some participants received 40 sessions. Clinical responders were 88.9% with hyperbaric oxygen against 62.5% with sham. The difference disappeared once the sham group crossed over to active treatment.

HOT2, 2016 (bowel symptoms). This UK double-blind, sham-controlled phase 3 trial, funded by Cancer Research UK, randomised 84 people with bowel symptoms lasting 12 months or more after pelvic radiotherapy. The active group had 40 sessions of 90 minutes at 2.4 ATA; the sham group breathed air at 1.3 ATA. At 12 months there was no significant difference in bowel symptom scores or rectal bleeding scores. The authors found "no evidence" of benefit and called for more high-quality trials.

RICH-ART, 2019 (cystitis). This randomised phase 2 to 3 trial at five Nordic university hospitals enrolled 87 people and analysed 79. The hyperbaric group had 30 to 40 daily sessions of 80 to 90 minutes at 240 to 250 kPa (roughly 2.4 to 2.5 ATA); the comparison group had standard care. There was no sham and no blinding. Urinary symptom scores improved by 10.1 points more in the hyperbaric group, and 41% of that group had temporary grade 1 to 2 side effects affecting sight or hearing. A 2025 follow-up of treated patients reported the improvement was still present at five years, with 39 people completing that assessment.

The overview. The 2023 Cochrane review of 18 trials and 1,071 participants concluded that hyperbaric oxygen may be associated with improved outcomes for late radiation injury of the head and neck, bladder and rectum, at low to moderate certainty, and that small studies demand cautious interpretation. It also found a higher risk of reduced visual sharpness, usually temporary, and of ear barotrauma.

Access in the UK. NHS England lists hyperbaric oxygen for soft tissue radiation damage after pelvic radiotherapy as not routinely commissioned, so any referral is a specialist decision that varies by area.

Where does HBOT Medics fit?

Two things should be clear. First, hyperbaric oxygen does not treat cancer, and we do not offer it for that purpose; our article on HBOT and cancer explains why these are separate questions. Second, every trial above used 2.0 to 2.5 ATA. Our single-person chamber runs at 1.5 ATA, so those results cannot be taken as what a course here would do.

If you have new bowel or bladder symptoms after pelvic radiotherapy, the first step is assessment by your GP or cancer team, not a chamber. Once serious causes have been ruled out, it is reasonable to ask your team whether a specialist hyperbaric referral has a place. If you are weighing up HBOT more generally, read what HBOT is and who it is not for. No referral needed. Medical consultation included.