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:
- Dietary indiscretion
- Antibiotic reaction
- Gastroenteritis/infective enteritis: common causes are:
–bacterial
- Salmonella sp.
- Campylobacter jejuni
- S. aureus (food poisoning)
- Clostridium perfringens
- enteropathic Escherichia coli
–viral
- rotavirus (50% of children hospital admissions)
- norovirus
Chronic:
- Irritable bowel syndrome (IBS), was the commonest cause of chronic diarrhoea in a UK study
- Drug reactions (e.g. laxatives)
- Coeliac disease
- Chronic infections such as giardiasis and cryptosporidium
Serious disorders not to be missed
Neoplasia/cancer:
- colorectal cancer
- ovarian cancer
- peritoneal cancer
Infection:
- cholera
- typhoid/paratyphoid
- amoebiasis
- malaria
- enterohaemorrhagic E. coli enteritis
- HIV infection (AIDS)
Others
- Inflammatory bowel disease
- pseudomembranous colitis
- Intussusception
- Pelvic appendicitis/pelvic abscess
Pitfalls (often missed)
- Coeliac disease
- Faecal impaction with spurious diarrhoea
- Lactase deficiency
- Giardia lamblia infection
- Cryptosporidium infection
- Malabsorption states (e.g. coeliac disease)
- Vitamin C and other oral drugs
- Nematode infections:
- strongyloides (threadworm)
- whipworm
- hookworm
- Radiotherapy
- Diverticulitis
- Post-GIT surgery
- Ischaemic colitis (elderly)
- Rarities:
- Addison disease
- carcinoid tumours
- short bowel syndrome
- amyloidosis
- toxic shock
- Zollinger–Ellison syndrome
Masquerades checklist
Diabetes
Drugs
Hyperthyroidism
Is the patient trying to tell me something?
Yes, diarrhoea may be a manifestation of;
- anxiety state or
- irritable bowel syndrome.
Key history
Establish what the patient means by diarrhoea.
Analyse the nature of the stools, frequency, associated symptoms (e.g. abdominal pain)
Constitutional symptoms such as fever and weight loss.
Drug history, travel history and FHx.
Key examination
Focus on the general state (esp. of severe gastroenteritis);
- abdomen
- rectum and
- skin
Ideally the stool should be examined, note;
- blood
- mucus
- steatorrhoea
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
- endoscopy
- selective radiology (e.g. small bowel enema).
Diagnostic tips
Giardiasis (profuse bubbly diarrhoea) is more common than realised.
Remember spurious diarrhoea and trectal exam in the elderly.
IBS rarely causes nocturnal diarrhoea but causes recurrent pain in the right hypochondrium.
Drugs that can cause diarrhoea:
- alcohol
- antibiotics
- digoxin
- colchicine
- cytotoxic agents
- H2-receptor antagonists
- iron compounds
- laxatives
- metformin
- sildenafil
- statins
- thyroxine.
Diagnostic triads for diarrhoea
Acute dia + colicky abdominal pain ± vomiting → gastroenteritis
(Young adult) dia ± 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 ± abdo discomfort → colorectal carcinoma
Diarrhoea (fluid/incontinent) + constipation ++ + abdo discom + anorexia/nausea → faecal impaction
Profuse watery dia. + abdo cramps (on antibiotics) → pseudomembranous colitis
Variable dia/constipation + abdo discomfort + mucus PR + flatulence ++ → irritable bowel syndrome
