Radiation Enteropathy

Radiation enteropathy is injury to the small bowel, colon or rectum from therapeutic or accidental irradiation, usually after pelvic or abdominal radiotherapy for cervical, prostate, rectal, endometrial or bladder cancer, retroperitoneal sarcoma or lymphoma. Cervical cancer is the dominant indication in Kenya. Acute enteritis occurs in 50 to 80 percent during or within 3 months of treatment; chronic radiation enteropathy affects 5 to 15 percent, appearing 3 months to many years later.

Acute injury results from epithelial crypt cell death and inflammation; chronic injury results from obliterative endarteritis, ischaemia and fibrosis, with dysmotility, strictures, adhesions, fistulas and bile acid malabsorption. Risks include total dose over 45 to 50 Gy, large treated volume, brachytherapy, concurrent chemotherapy, previous abdominal surgery, inflammatory bowel disease, diabetes, vascular disease, thin body habitus and smoking.

Bowel loops fixed in the pelvis by adhesions receive the highest doses. Late radiation proctitis often bleeds; small bowel strictures cause obstruction.

• Acute: nausea, anorexia, diarrhoea, cramping abdominal pain, tenesmus, mucus, rectal bleeding.
• Chronic: diarrhoea (bile acid malabsorption, bacterial overgrowth, steatorrhoea), faecal urgency and incontinence, rectal bleeding from telangiectasia, weight loss, vitamin B12, fat soluble vitamin and mineral deficiencies.
• Strictures: colicky pain, vomiting, intermittent subacute obstruction.
• Perforation, abscess, fistula (rectovaginal, enterovesical, enteroenteric) with faecaluria or vaginal faeces.
• Chronic anaemia, malnutrition, short bowel syndrome after resections.
• Red flags: peritonism, obstruction, heavy rectal bleeding, fever, faecal or air fluid vaginal discharge, new weight loss (exclude recurrent tumour).

• Clinical history of radiotherapy (dose, fields, brachytherapy) and timing.
• Blood tests: full blood count, ferritin, B12, folate, albumin, vitamin D, magnesium, zinc, prothrombin time, C-reactive protein.
• Stool: culture, Clostridioides difficile toxin, ova and parasites, faecal calprotectin.
• Endoscopy: sigmoidoscopy or colonoscopy shows pallor, friability, telangiectasia, ulcers, strictures; biopsy to exclude cancer recurrence and inflammation (avoid deep biopsies in anterior rectal wall near a fistula).
• Imaging: CT or MR enterography shows bowel wall thickening, strictures, fistula, and abscess; contrast enema; small bowel follow through; capsule endoscopy (with caution for stricture and a patency capsule first).
• Tests for malabsorption: hydrogen breath test for bacterial overgrowth (glucose 75 g; rise of 20 ppm within 90 minutes), 75Se-homotaurocholic acid retention test (SeHCAT, below 10 percent at 7 days indicates bile acid malabsorption) or a therapeutic trial of colestyramine.
• Exclude tumour recurrence, infectious colitis, ischaemic colitis, inflammatory bowel disease, and Clostridioides difficile infection.

• Acute enteritis: oral rehydration, low residue, low lactose diet; loperamide 4 mg orally then 2 mg after each loose stool, maximum 16 mg per day; ondansetron 8 mg orally every 8 hours for nausea; hyoscine butylbromide 10 to 20 mg orally every 6 hours for cramps; avoid sulfasalazine and prophylactic steroid enemas. Interrupt radiotherapy for grade 3 toxicity.
• Acute proctitis: hydrocortisone 100 mg in 50 mL as a retention enema nightly for 14 days, or hydrocortisone acetate 10 percent rectal foam twice daily for 14 days; sucralfate 2 g in 20 mL enema twice daily for 4 weeks may be used.
• Chronic bile acid diarrhoea: colestyramine 4 g orally once or twice daily increased to 4 g four times daily, taken 1 hour before or 4 to 6 hours after other medicines (avoid binding of fat soluble vitamins; replace them); colesevelam 625 mg tablets, 3 tablets daily, if available.
• Small intestinal bacterial overgrowth: rifaximin 550 mg orally three times daily for 14 days, or ciprofloxacin 500 mg twice daily for 7 days, repeated in cycles or rotated antibiotic courses as needed.
• Rectal bleeding from telangiectasia: argon plasma coagulation at 1 to 3 sessions, 4 weeks apart (power 30 to 40 W, flow 1 to 2 L/min); 4 percent formalin 50 to 100 mL topically on the rectum for diffuse bleeding (anaesthesia and care to avoid anal burns); oral iron (ferrous sulfate 200 mg three times daily) or intravenous iron (iron sucrose 200 mg on 5 occasions over 2 weeks) for anaemia; tranexamic acid 1 g orally three times daily for 5 days for bleeding.
• Nutrition: dietician led, fat restricted diet with medium chain triglycerides, vitamin B12 1 mg intramuscularly every 3 months, replacement of fat soluble vitamins; parenteral nutrition for intestinal failure.
• Pentoxifylline 400 mg three times daily with tocopherol 1000 IU daily for 6 to 12 months may reduce fibrosis.
• Hyperbaric oxygen at 2.0 to 2.4 atmospheres for 90 minutes daily for 30 sessions for refractory proctitis.
• Surgery for obstruction, perforation, fistula or unremitting bleeding: bypass or resection with a primary anastomosis, and a defunctioning stoma for fistula; operate in a dedicated centre, using wide resection to well vascularised margins, as the operative mortality is 5 to 10 percent and anastomotic leak up to 30 percent.
• Follow up: every 3 months for the first year; colonoscopy at 5 years then 5-yearly for surveillance of radiation associated colorectal cancer.
• Prevention: bladder filling and belly boards, intensity modulated radiotherapy, omentum or mesh to displace small bowel, and avoiding dose escalation.