The clinical assessment of chronic diarrhoea

Key points

A wide number of possibilities need to be considered
Classic steatorrhea is not common in malabsorption
A systematic history usually identifies the likely cause or mechanism
Basic screening tests of the stool and blood tests looking for causes and complications
Confirmatory testing usually requires imaging or endoscopic (+/- specific tests for malabsorption)
Empiric treatment for protozoan infection is reasonable before expensive testing

Standard history taking

SOCRATES method (site, origin/onset, character/chronology. relieving, aggrating/alleviating/associated, time course, exacerbating, severity)

• Perpetuating - alcohol, chronic hepatitis
• Precipitant – food/waterborne contact, institution (school, nursing home, gaol) > acute infectious, travel > dysentery
• Chronology – not at night > IBS,
• Aggravating - stress > IBS
• Alleviating - defecation > IBS
• Associated - temporal relationship with pain and stool alteration > IBS

PHx - GIT surgery, liver or bililary disease, pancreatic disease, thyroid disorders

FHx - Coeliac disase, IBD, lactose intolerance, cystic fibrosis

Meds / Drugs - alcohol, laxative, IVDU, transfusion history

Sexual history - unsafe sex practices, anal sex

By syndrome

• Malabsorption – staetorrhea, weight loss & muscle atrophy, FHx - cystic fibrosis, coeliac disease, IBD, lactose intolerance
• Inflammatory – blood > colitis (IBD, post-antibiotic) or dysenteric (salmonella, shigella, campylobacter), FHx - IBD
• Osmotic / Secretory - watery
• Functional / Motility – not at night > IBS, colonoscopy normal, thyrotoxic or hypothyroid symptoms

By complication

• Water loss - dehydration, shock
• Nutrient loss - muscle atrophy (protein), anaemia (Vit B12, folate, iron), osteoporosis, neurological symptoms (Vit D, calcium), bruising/bleeding (Vit K), night blindness (Vit A)

 By anatomy

• stomach - surgery, PPI
• small bowel - surgery, mucosal
• pancreatic - alcohol
• liver - alcohol, viral hepatitis, biliary disease
  

Malabsorption

by physiological process

• Digestive - enzymatic defect/inactivation (pancreatic insufficiency), v bile (liver disease) /^ bile > deconjugated (biliary disease), other - ^ v gastric pH, v intrinsic factor, bacterial overgrowth
• Absorptive - enzymatic defect (lactose deficiency), v mucosal transport (Coeliac), motility (IBS)
• Post-absorptive - lipoprotein defects (abetalipoproteinaemia), GI lymphatic disease (lymphectasia)
  

by pathological sieve / aetiology

• Immunological - coeliac (FHx) , HIV (risk behaviours)
• Neoplastic - GIT lymphoma, rare GI tumours e.g. VIPoma (weight loss)
• Infective - post-infective (infective contacts)
• Toxic - alcohol, laxative (drug and alcohol history)
• Trauma - post surgery (surgical history)

Initial tests

• Stool culture
• Stool parasites
• Stool fat
• FBC - anaemia, infection
• EUC - electrolyte abnormality
• LFTs - liver disease, biliary disease

Advanced tests

• Specific malabsorption tests
• Abdominal ultrasound
• Small bowel series
• Endoscopy, Colonoscopy