Diarrhoea

INTRODUCTION

Diarrhoea is defined as the frequent passage of loose or watery stools. Essential features are:

• an increase in frequency of bowel action

• an increase in softness, fluidity or volume of stools

PROBABILITY DIAGNOSIS

Acute diarrhoea

Common causes are:

• gastroenteritis

  • – bacterial

    • Salmonella sp.

    • Campylobacter jejuni

    • S. aureus (food poisoning)

    • Clostridium perfringens

    • enteropathic Escherichia coli

  • – viral

    • rotavirus (50% of children hospital admissions)

    • norovirus

    • dietary indiscretions (e.g. binge eating)

    • antibiotic reactions

Chronic diarrhoea Irritable bowel syndrome was the commonest cause of chronic diarrhoea in a UK study.

Drug reactions, coeliac disease and chronic infections such as giardiasis and cryptosporidium are also important causes.

Key investigations In some instances, such as acute self-limiting diarrhoea, nil is required. Consider:

• microscopy and culture of stool

• FBE

• ESR/CRP

• C. difficile tissue culture assay

• U&E

• specific tests for organisms

• antibody tests, e.g. coeliac disease; PCR

• endoscopy

• selective radiology (e.g. small bowel enema)

Red flags Unexplained weight loss, blood in stool, fever, overseas travel, severe abdominal pain, persistent diarrhoea, family history (bowel cancer), Crohn disease

Diagnostic triads for diarrhoea

• Acute diarrhoea + colicky abdominal pain ± vomiting → gastroenteritis

• (Young adult) diarrhoea ± blood & mucus + abdominal cramps → inflammatory bowel disease (UC/Crohn)

• As above + constitutional symptoms ± eyes/joints → Crohn disease

• Pale bulky offensive stools, difficult to flush, weight loss → malabsorption

• Fatigue + weight loss + iron deficiency → coeliac disease

• Failure to thrive (child) + recurrent chest infections → cystic fibrosis

• Altered bowel habit ± diarrhoea ± constipation ± rectal bleeding ± abdominal discomfort → colorectal carcinoma

• Diarrhoea (fluid/incontinent) + constipation ++ abdominal discomfort + anorexia/nausea → faecal impaction

• Profuse watery diarrhoea + abdominal cramps (on antibiotics) → pseudomembranous colitis

• Variable diarrhoea/constipation + abdominal discomfort + mucus PR + flatulence + → irritable bowel syndrome

SPECIFIC CONDITIONS

Pseudomembranous colitis (antibiotic-associated diarrhoea)

This potentially fatal colitis can be initiated by the use ...