Day 6 of piperacillin-tazobactam; 8 loose stools/day, cramping, WCC 22 × 10⁹/L, albumin falling
ABCDE
Isolate with contact precautions and soap-and-water hand hygiene, stop the precipitating antibiotic where possible, rehydrate — and examine the abdomen for the toxic megacolon that turns this into a surgical emergency.
Test only unformed stool → two-step testing (GDH/NAAT plus toxin EIA); never test formed stool and never re-test to prove cure — carriage persists for weeks
First episode, non-severe or severe → oral fidaxomicin 200 mg BD × 10 days, or vancomycin 125 mg QDS × 10 days. Metronidazole only where neither is available
Fulminant (hypotension, ileus, megacolon) → vancomycin 500 mg QDS orally or by NG tube, PLUS metronidazole 500 mg IV q8h, PLUS vancomycin retention enema if there is ileus — and call surgery early
Recurrence → fidaxomicin or a tapered-pulsed vancomycin course, and add bezlotoxumab or refer for faecal microbiota transplantation after multiple recurrences
Diarrhoea but toxin-negative → look at the feed rate and osmolality, sorbitol-containing and magnesium-containing drugs, laxatives, prokinetics, ischaemia, overflow around impaction, and other enteric pathogens
Order set
- Contact isolation, soap and water
- Stool for C. difficile (unformed only)
- Stop/narrow the precipitating antibiotic
- Stop antimotility agents and PPI review
- FBC, U&E, albumin, lactate
- Erect abdominal film or CT if distended
- Fluid and electrolyte replacement
Criteria
AdmitAny confirmed infection with systemic features
ICUFulminant colitis, lactate rise, ileus, toxic megacolon, or need for vasopressors
DischargeStool frequency settling, eating and drinking, 10-day course planned
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Rising lactate with abdominal distension
- Colonic diameter above 6 cm
- Sudden cessation of diarrhoea with a distending abdomen
- Hypotension or new vasopressor requirement
Differentials
- Enteral feed intolerance
- Drug-induced diarrhoea (magnesium, sorbitol elixirs, laxatives)
- Ischaemic colitis
- Overflow around faecal impaction
- Other enteric infection
- Inflammatory bowel disease
Common mistakes
- Giving IV vancomycin — it does not reach the colon
- Alcohol gel instead of soap and water
- Re-testing to confirm cure
- Loperamide in colitis
- Delaying the surgical referral in fulminant disease
Disposition & follow-up
Ten-day course completed on the ward; colectomy decision is a joint surgical and critical care call taken before lactate climbs, not after.
Discharge package
MedicationsComplete fidaxomicin or vancomycin; review every antibiotic and the PPI
Follow-upGP and infection team review; readmit early on recurrence
LifestyleHousehold hygiene advice; probiotic evidence is weak
Warning symptomsReturn of frequent diarrhoea, fever, severe abdominal pain or distension
💊 Treatment detail — doses & preparation
Fidaxomicinmacrocyclic antibiotic
Dose200 mg orally twice daily × 10 days
PreparationTablets; acts locally in the colon
MonitorFewer recurrences than vancomycin; poorly absorbed
Vancomycin (oral)glycopeptide
Dose125 mg QDS × 10 days; 500 mg QDS in fulminant disease
PreparationOral capsules, or the IV preparation given orally/per NG; 500 mg in 100 mL saline as a retention enema
MonitorNot absorbed — no levels needed; check for ileus
Metronidazole (IV, fulminant only)nitroimidazole
Dose500 mg IV every 8 hours, added to oral vancomycin
PreparationIn 100 mL over 20 min
MonitorNeuropathy if prolonged; avoid alcohol
📖 IDSA/SHEA C. difficile 2021 update · ESCMID 2021 · ICU chapter 42 · C. diff & ICU DiarrheaReviewed September 2026