Radiation Proctopathy

Radiation proctopathy is injury to the rectal mucosa and wall caused by pelvic radiotherapy for prostate, cervical, endometrial, rectal, bladder or anal cancers.

• Acute injury occurs within 3 months; chronic injury appears after 3 months, typically 6 to 24 months, but can occur many years later.
• Chronic injury is caused by obliterative endarteritis, ischaemia, fibrosis and neovascularisation (telangiectasia).
• Risk factors: total dose above 70 Gy, large volume, brachytherapy, concurrent chemotherapy, prior abdominopelvic surgery, diabetes, hypertension, inflammatory bowel disease, vascular disease, smoking and HIV.

Acute: diarrhoea, tenesmus, urgency, mucus, cramping, pain.

• Chronic: rectal bleeding (the commonest symptom, from telangiectasia), tenesmus, urgency, frequent small stools, mucous discharge, faecal incontinence, rectal pain.
• Late structural changes: stricture, ulcers, fistulae (rectovaginal, rectovesical), perforation, necrosis.
• Differential diagnosis: recurrent or new tumour, inflammatory bowel disease, infectious proctitis, ischaemic proctitis, haemorrhoids, solitary rectal ulcer, colorectal polyps, diverticular disease, gastrointestinal bleeding from other sources.
• Complications: iron deficiency anaemia, transfusion dependence, stricture with obstruction, fistula, incontinence, sepsis, malnutrition and reduced quality of life.

Proctoscopy or flexible sigmoidoscopy shows pallor, friability, telangiectasia, ulceration, strictures; take care not to biopsy anterior rectal wall ulcers (risk of non-healing ulcer or fistula).

• Full blood count and ferritin; exclude recurrence or second primary with MRI pelvis or CT, and serum tumour markers where relevant.
• Stool culture and Clostridioides difficile toxin during acute symptoms.
• Biopsy only if malignancy is suspected, from non-anterior sites.

Supportive: low residue diet during acute injury, fluids, iron replacement (ferrous sulfate 200 mg daily or intravenous ferric carboxymaltose 1000 mg), transfusion for haemoglobin below 7 g/dL, nutrition support.

Pharmacological

• Acute diarrhoea: loperamide 4 mg then 2 mg after each loose stool (maximum 16 mg daily); acute tenesmus or pain: hydrocortisone 100 mg retention enema nightly for 2 weeks or budesonide foam 2 mg nightly.
• Chronic bleeding: sucralfate enema 3 g in 20 mL water twice daily for 4 weeks (or 2 g twice daily); metronidazole 400 mg three times daily for 4 weeks; short chain fatty acid enemas (butyrate) twice daily for 3 to 4 weeks.
• Stool softener to reduce straining.

Procedures

• Argon plasma coagulation (power 40 to 60 W, flow 1 to 2 L/min, short bursts of 1 to 2 seconds) every 4 to 6 weeks until bleeding stops (success above 80 percent).
• Topical formalin 4 percent applied with a gauze soaked in formalin, or by instillation of 100 mL; rare risk of necrosis and stricture, requires anal protection.
• Hyperbaric oxygen, 30 to 40 sessions of 90 minutes at 2.0 to 2.4 atmospheres.
• Radiofrequency ablation, cryotherapy, or bipolar coagulation as alternatives.
• Surgery (diverting stoma, resection, stricture dilation) for fistula, perforation, obstruction and intractable bleeding.

Special groups: elderly and prostate cancer patients (anticoagulants worsen bleeding), HIV (lower threshold for investigation).

Red flags: heavy bleeding with haemodynamic compromise, faecal soiling through vagina or urine, obstruction, pelvic pain, signs of recurrence.

Follow-up: review at 6 to 8 weeks after each argon plasma session; haemoglobin and ferritin at 3 months; colonoscopy surveillance for malignancy.