Nonsteroidal Anti-Inflammatory Drug Colopathy

Nonsteroidal anti-inflammatory drug (NSAID) colopathy is colonic injury attributable to NSAIDs, including colitis, discrete ulcers, diaphragm like strictures, haemorrhage and perforation. It can also precipitate flares of inflammatory bowel disease and complications of diverticular disease.

It is less common than upper gastrointestinal injury. NSAIDs account for a notable fraction of lower gastrointestinal bleeding and of perforated diverticulitis, and risk is highest in older adults.

Risk factors are older age, long term use, slow release formulations (diclofenac, mefenamic acid and others), diverticulosis, prior colitis, concurrent aspirin, corticosteroids or anticoagulants.

Pathophysiology.

Prostaglandin depletion and direct epithelial toxicity reduce mucosal defence and blood flow. Enterohepatic recirculation of the drug and bile acids concentrates exposure in the right colon, and in the caecum and ascending colon.

Bloody or watery diarrhoea, abdominal pain, anaemia, protein loss, and obstruction from strictures. Perforation presents with peritonitis.

Red flags.

• Peritonitis or free air.
• Massive rectal bleeding.
• Vomiting with colicky pain (stricture).

Colonoscopy shows discrete punched out ulcers (commonly caecal and right colon), segmental colitis or concentric diaphragm like webs. Biopsy shows non-specific inflammation with increased apoptosis and eosinophils, and excludes inflammatory bowel disease and infection. Exclude Clostridioides difficile and cytomegalovirus. CT shows wall thickening and complications.

Differential diagnosis.

• Ulcerative colitis or Crohn disease.
• Ischaemic colitis.
• Infective colitis (cytomegalovirus, Clostridioides difficile).
• Colonic cancer.
• Diverticular colitis.
• Microscopic colitis.

Stop the NSAID. Most lesions heal in weeks, and symptoms settle within 1 to 2 weeks of withdrawal.

• Paracetamol: 1 g orally every 6 hours as needed for pain; maximum 4 g daily; monitor liver enzymes in long courses; reduce to 2 to 3 g daily if under 50 kg, malnourished, or in hepatic impairment or chronic alcohol use.
• Ferrous sulphate: 200 mg orally once daily or on alternate days until ferritin is over 100 microgram/L plus 3 months; maximum 200 mg three times daily; monitor haemoglobin and ferritin; reduce frequency for intolerance.

Manage bleeding by resuscitation, with transfusion at haemoglobin 70 g/L (80 g/L with cardiovascular disease), and endoscopic haemostasis. Treat strictures by endoscopic balloon dilation or resection. Surgery is needed for perforation, uncontrolled bleeding and fixed obstruction. Do not use mesalazine or corticosteroids unless a separate inflammatory condition is proven.

Monitoring. Repeat colonoscopy at 8 to 12 weeks to confirm healing and exclude cancer; haemoglobin until normal.

Referral and escalation. Gastroenterology; colorectal surgery for complications.