Approach to Acute Watery Diarrhoea | PACES Pathfinders Learning Library

Overview

Acute watery diarrhoea is a common medical presentation in both hospital and community practice. Initial assessment should focus on the severity of dehydration, haemodynamic stability and identification of infective or medication-related causes. In hospitalised patients, recent exposure to broad-spectrum antibiotics should immediately raise suspicion of Clostridioides difficile infection. Early diagnosis, prompt fluid resuscitation, appropriate infection control measures and targeted antimicrobial therapy are essential to reduce the risk of serious complications such as pseudomembranous colitis, toxic megacolon and perforation. :contentReference[oaicite:2]{index=2}

Structured History

Characterise the Diarrhoea

Onset and duration
Frequency (day and night)
Volume and consistency
Progression of symptoms
Presence of blood, mucus or pus
Nocturnal diarrhoea

Associated Symptoms

Abdominal cramps or diffuse pain
Abdominal distension
Nausea or vomiting
Fever or rigors
Thirst or dizziness suggesting dehydration
Reduced urine output

Identify the Cause

Recent antibiotic use
Recent hospital admission
Recent surgery
Laxative use
Recent travel
Contact with individuals who have diarrhoea
Suspicious food intake

Red Flag Symptoms

Weight loss
Loss of appetite
Persistent altered bowel habit
Rectal bleeding
Previous inflammatory bowel disease
Family history of colorectal cancer

Past Medical History

Inflammatory bowel disease
Previous C. difficile infection
Immunosuppression
Chronic respiratory disease
Malignancy
Endocrine disorders (e.g. thyroid disease)

Examination

Assess airway, breathing and circulation
Review temperature, pulse, blood pressure and respiratory rate
Assess hydration (mucous membranes, skin turgor, capillary refill and postural hypotension)
Assess nutritional status
Examine the abdomen for tenderness, guarding or distension
Assess bowel sounds
Look for features of toxic megacolon
Look for clubbing if inflammatory bowel disease or colorectal malignancy is suspected
Review fluid balance charts
Assess urine output

Differential Diagnosis

Clostridioides difficile Infection Antibiotic-associated Diarrhoea Viral Gastroenteritis Food Poisoning Inflammatory Bowel Disease Legionella Infection Mycoplasma Infection Colorectal Cancer Hyperthyroidism

Investigations

Baseline Blood Tests

Full blood count
Urea, electrolytes and creatinine
C-reactive protein and ESR
Liver function tests
Thyroid function tests where clinically indicated

Stool Investigations

Stool microscopy and culture
C. difficile toxin assay
PCR for C. difficile where available
Faecal inflammatory markers if appropriate

Imaging

Abdominal X-ray if ileus or toxic megacolon is suspected
CT abdomen if perforation or severe colitis is suspected

Additional Tests

Urinary Legionella antigen if clinically suspected
Respiratory samples for atypical pneumonia where appropriate
Colonoscopy after recovery if persistent altered bowel habit or colorectal cancer is suspected

Diagnosis

Acute Watery Diarrhoea Secondary to Clostridioides difficile Infection

In a hospitalised patient who develops acute watery diarrhoea after recent broad-spectrum antibiotic therapy, Clostridioides difficile infection should be strongly suspected. Confirmation is obtained by stool toxin or PCR testing, while investigations also help exclude alternative causes and identify complications such as dehydration, ileus or toxic megacolon. :contentReference[oaicite:1]{index=1}

Management

Immediate Care Assess severity, commence intravenous fluids where required, correct electrolyte disturbances and stop unnecessary laxatives.

Treat the Cause Review ongoing antibiotic therapy, discontinue the offending antibiotic whenever possible, and commence appropriate therapy for Clostridioides difficile infection according to current guidelines.

Prevent Transmission Institute contact precautions, isolate the patient, reinforce hand hygiene with soap and water, and monitor closely for toxic megacolon, perforation or recurrent infection.

Explaining to the Patient

"Your diarrhoea is most likely related to the antibiotics used to treat your chest infection. Sometimes antibiotics disturb the normal bacteria in the bowel, allowing another bacterium called Clostridioides difficile to grow. We will send stool samples to confirm the diagnosis, replace the fluids you have lost, review your antibiotics and begin the appropriate treatment. We will also take precautions to reduce the risk of spreading the infection to other patients."

Examiner's Corner

How do you recognise Clostridioides difficile infection?

Recent exposure to broad-spectrum antibiotics.
Recent hospital admission or healthcare exposure.
Acute profuse watery diarrhoea.
Abdominal cramps with leucocytosis.
Positive stool toxin assay or PCR confirms the diagnosis.

What are the major complications?

Severe dehydration.
Acute kidney injury.
Electrolyte disturbances.
Pseudomembranous colitis.
Toxic megacolon.
Bowel perforation.
Sepsis.
Recurrent infection.

How can recurrence be reduced?

Avoid unnecessary antibiotic exposure.
Use guideline-directed therapy.
Review proton pump inhibitor use.
Optimise infection control measures.
Consider specialist therapies for recurrent disease where appropriate.

How do you differentiate common causes of acute diarrhoea?

Cause	Typical Clue
Clostridioides difficile	Recent antibiotics or hospital admission
Viral gastroenteritis	Vomiting with short self-limiting illness
Food poisoning	Multiple affected individuals after a shared meal
Inflammatory bowel disease	Blood, mucus and chronic symptoms
Traveller's diarrhoea	Recent foreign travel

Common Viva Questions

Which antibiotics most commonly predispose to Clostridioides difficile infection?
How is the diagnosis confirmed?
When should abdominal imaging be requested?
What are the features of toxic megacolon?
How should infection control be implemented?
Which patients are at greatest risk of recurrence?
When should surgery be considered?

Important Clinical Pearls

Always ask about recent antibiotic exposure in any patient with acute diarrhoea.
Assess hydration status before focusing on the specific diagnosis.
Review medication charts for antibiotics, laxatives and proton pump inhibitors.
Institute contact precautions immediately when Clostridioides difficile is suspected.
Early recognition of toxic megacolon can be lifesaving.

At a Glance

Red Flags

PACES Approach

Acute Watery Diarrhoea Framework

Clostridioides difficile Clues