AKT · Gastroenterology/Colon & rectum

Infectious colitis (incl. C. difficile)

Colonic infection — Clostridioides difficile (antibiotic-associated), or invasive bacteria (Shigella/Campylobacter/E. coli/Salmonella)

Overview

Infectious inflammation of the colon. Clostridioides difficile (antibiotic-associated pseudomembranous colitis — toxin-mediated, after broad-spectrum antibiotics, esp. the '4 Cs': clindamycin, cephalosporins, co-amoxiclav, ciprofloxacin/quinolones) causes watery/bloody diarrhoea, with toxic megacolon as the feared complication. Invasive bacterial colitis (Shigella, Campylobacter, EHEC, Salmonella) causes bloody diarrhoea (dysentery). Managed by stopping the offending antibiotic + targeted therapy + infection control.

Recognise

C. difficile: watery (± bloody) diarrhoea, fever, abdominal pain, raised WCC, after recent antibiotics/hospitalisation/PPI; pseudomembranes on sigmoidoscopy
Invasive bacterial: bloody diarrhoea (dysentery), fever, cramps; travel/food/contact history
Complications: dehydration, toxic megacolon (C. diff), HUS (EHEC O157 — avoid antibiotics)

Red flags

C. difficile with toxic megacolon, ileus, shock, or rising lactate/WCC → severe disease, surgical input
EHEC O157 → do NOT give antibiotics (precipitates HUS); HUS (AKI + haemolysis + thrombocytopenia)

Differentials & how to tell them apart

Inflammatory bowel disease flarechronic relapsing, raised calprotectin — but exclude/superimposed infection

Ischaemic colitisolder, watershed, vascular risk

Viral/non-invasive gastroenteritiswatery, self-limiting, no dysentery

Antibiotic-associated diarrhoea (non-C.diff)milder, toxin-negative

Investigations

Stool C. difficile testing (GDH + toxin/PCR); stool culture (bacterial pathogens); FBC/U&Es/CRP/lactate; AXR if toxic megacolon suspected. Flexible sigmoidoscopy (pseudomembranes) if needed.

Management

Stop the antibiotic + oral vancomycin (C. diff); supportive care + infection control

1C. difficile: stop the offending antibiotic, start ORAL VANCOMYCIN (10 days), isolate the patient, hand-wash with soap and water (spores resist alcohol gel). Supportive fluids; avoid antimotility drugs.Gate: In suspected EHEC O157 (bloody diarrhoea, child) do NOT give antibiotics or antimotility agents — they raise HUS risk; severe C. diff (toxic megacolon/shock) needs surgical assessment (fidaxomicin/colectomy)
2Recurrent C. diff → fidaxomicin or faecal microbiota transplant; severe/fulminant → IV metronidazole + oral/PR vancomycin ± colectomy; treat dehydration; notify/public-health for relevant pathogens.

Stop the causative antibiotic; oral vancomycin (first-line C. diff) — oral vancomycin 10 days; fidaxomicin for recurrence; metronidazole only if others unavailable

Infection control (isolation, hand-washing with soap — alcohol gel doesn't kill spores) — prevent spread

Supportive (fluids); avoid antimotility agents — loperamide can precipitate toxic megacolon in C. diff/invasive colitis

Key points

Diarrhoea after antibiotics (the 4 Cs) + raised WCC = C. difficile → stop the antibiotic, oral vancomycin, soap-and-water (not gel), no loperamide. Bloody diarrhoea + child + EHEC = no antibiotics (HUS). Toxic megacolon is the emergency.

Monitor & prognosis

WCC/lactate, hydration, AXR (toxic megacolon); recurrence.

Good; severe/recurrent C. diff is morbid.

Source: NICE NG199 (C. difficile); UKHSA