Acute Diarrhoea & C. difficile (C. diff)

Acute diarrhoea is a common problem on medical wards and can range from mild self-limiting illness to severe, life-threatening colitis.
A key concern in hospital is Clostridioides difficile infection (C. diff), particularly in older or vulnerable patients.

This guide focuses on what doctors actually need to recognise and manage on the ward and on-call.

What counts as acute diarrhoea?

New onset diarrhoea (usually <14 days duration), typically defined as:

  • ≥3 loose stools per day
  • Change from baseline bowel habit

In hospital, always consider:

Is this simple gastroenteritis — or could this be C. diff?

Typical presentations

  • Frequent loose stools
  • Abdominal cramps
  • Fever
  • Nausea / vomiting
  • Dehydration
  • Reduced oral intake

More concerning features:

  • Severe abdominal pain
  • Blood in stool
  • Fever and tachycardia
  • Hypotension
  • Confusion (especially elderly)

Common causes (think practically)

On the wards, most cases fall into a few patterns.

Community-related:

  • Viral gastroenteritis
  • Food poisoning
  • Recent travel

Hospital-related:

  • C. difficile infection
  • Antibiotic-associated diarrhoea
  • Laxatives
  • Enteral feeds
  • Overflow diarrhoea (constipation)

Always check:

  • Drug chart
  • Recent antibiotics
  • Stool history
  • Baseline bowel habit

On the ward, always ask:

Has this patient had antibiotics in the last 3 months?

Because this significantly increases the risk of C. diff infection.

First priority = Assess severity and hydration

Before focusing on cause, assess the patient.

Look at:

  • Hydration status
  • BP and HR
  • Urine output
  • Mental state
  • Temperature
  • Abdominal exam (distension, tenderness)

Red flags:

  • Tachycardia
  • Hypotension
  • Fever
  • Severe abdominal pain
  • Reduced urine output
  • Confusion

These suggest sepsis, severe colitis, or dehydration and need escalation.

Immediate management on the ward (what juniors should actually do)

If you are asked to review a patient with acute diarrhoea:

Do immediately:

  • Full set of observations
  • Assess hydration
  • Review medications (stop laxatives if present)
  • Check recent antibiotics
  • Stool chart
  • Strict fluid balance

Bloods:

  • FBC
  • U&E
  • CRP
  • LFTs (if unwell)

Fluids:

  • Encourage oral fluids
  • IV fluids if dehydrated or hypotensive

When to suspect C. difficile

Think C. diff if:

  • Diarrhoea develops in hospital
  • Recent antibiotics
  • Age >65
  • Frailty or comorbidities
  • Raised WCC / CRP
  • Fever
  • History of previous C. diff

What to do if you suspect C. diff

Do not delay this.

Send stool sample:

  • Stool for C. diff toxin and PCR

Infection control:

  • Isolate patient
  • Side room if possible
  • Gloves and apron
  • Inform nursing staff

Treatment (after confirmation or strong suspicion):

  • Usually oral vancomycin for confirmed cases
  • Follow local microbiology / trust guidelines

Always:

  • Discuss with seniors or microbiology if unsure.

When to escalate

You should escalate urgently if:

  • Severe abdominal pain
  • Marked abdominal distension
  • Hypotension
  • Tachycardia
  • Fever with rising inflammatory markers
  • Rising creatinine
  • Worsening clinical picture

These patients may have:

  • Severe C. diff colitis
  • Toxic megacolon
  • Sepsis
  • Risk of perforation

They need:

  • Senior review
  • Possible surgical input
  • Possible HDU care

Common mistakes juniors make

  • Forgetting to check recent antibiotics
  • Not sending stool sample early
  • Delaying isolation
  • Assuming all diarrhoea is “just laxatives”
  • Not assessing hydration properly
  • Forgetting to review drug chart

Take-home concept

Acute diarrhoea on the ward is rarely just about the stool.
It is about recognising who is unwell, who is dehydrated, and who might have C. diff — and acting early to prevent deterioration and outbreaks.