see also:

• gastroenteritis
• The child with gastroenteritis
• traveller's diarrhoea
• food poisoning
• osmotic diarrhoea from excessive solutes:
  • ingestion of too much solutes which either cannot be absorbed or exceed the capacity for absorption
  • eg. lactose, fructose, aspartame, saccharine, sorbitol, laxatives
  • may also occur post-cholecystectomy or after radiation Rx or chemoRx
  • some medications may contribute
• diverticulitis
• colitis
  • ulcerative colitis
  • Crohn's disease
  • pseudomembranous colitis
  • Yersiniosis
• irritable bowel syndrome (IBS)
• enteropathy
  • coeliac disease
  • HIV / AIDS
  • lymphoma
  • protein losing enteropathy (eg. cow's milk allergy)
• post-prandial diarrhoea
• colorectal cancer (bowel cancer)
• overflow faecal incontinence from faecal impaction
• chronic diarrhoea
  • hyperthyroidism
  • malabsorption
  • chronic alcohol abuse
• rare causes:
  • portal vein thrombosis

• diarrhoea is usually defined as loose or watery stools more than 3 times a day

• the general classification of causes are:
  • secretory diarrhoea - as with many types of gastroenteritis eg. cholera
  • osmotic diarrhoea due to non-absorbed solutes in the bowel which draws water into the bowel lumen
  • exudative diarrhoea and dysentery - results in blood or pus in the stool eg. Crohn's disease, Salmonella, etc
  • inflammatory diarrhea - results from damage to the brush border and inability to absorb protein-rich fluids but in these situations there is often a mix of the above types of diarrhoea
  • overflow passage of loose stool may occur in people with faecal impaction

• gastroenteritis is by far the most common cause of both V&D
• toxins including venoms
  • ciguatera toxin reef fish food poisoning - also develop neurologic symptoms
  • blue-green algae (BGA) toxins in waterways
• other infections
• chemotherapy including methotrexate
• radiation therapy
• chronic V&D:
  • Crohn's disease
  • ulcerative colitis
  • irritable bowel syndrome (IBS)
  • parasitic infections
• rare causes:
  • disseminated malignancy involving GIT - eg. melanoma
  • coeliac disease
  • whipple disease
  • lymphangiectasia
  • Zollinger-Ellison syndrome
  • protein losing enteropathy
  • portal vein thrombosis

• bloody diarrhoea
  • usually due to invasive bacterial pathogens such as Campylobacter jejuni, Shigella, Salmonella and enterohaemorrhagic E.coli (EHEC)
  • colitis such as:
    • ulcerative colitis
  • diverticulitis
  • exclude melaena as a cause of dark loose stools as this could be life threatening! - do a PR if in doubt!
• generally non-bloody diarrhoea
  • could it be overflow incontinence due to feacal impaction? Do a PR if this is possible.
  • Clostridium perfringens food poisoning (watery diarrhea without vomiting within 8-14 hours of ingestion)
  • gastroenteritis eg. norovirus, Enterotoxigenic E. coli, Campylobacter, giardiasis, Cryptosporidium parvum, Shigella sonnei, Salmonella, rotavirus
    • if immunocompromised such as organ transplant patients, consider also:
      • cytomegalovirus (CMV), Clostridium difficile, Entamoeba histolytica, Blastocystis hominis
      • Post Transplant Lymphoproliferative Disorder
      • Graft-vs-Host Disease
      • colorectal cancer (bowel cancer)
      • inflammatory bowel disease (IBD)
      • bacterial overgrowth syndromes
  • traveller's diarrhoea usually E.coli but also including cholera, typhoid, etc.
  • antibiotic-related diarrhoea including Clostridium difficile
  • laxatives
  • other medications causing diarrhoea
  • irritable bowel syndrome (IBS), stress, anxiety
  • malabsorption including food “allergies” / inability to absorb certain sugars when ingested in excess such as post-gastro lactose intolerance, FODMAP foods, etc.
  • proctitis
    • gonococcus
    • Herpes simplex virus (HSV)
    • radiation
  • colorectal cancer (bowel cancer)
  • Surgical resection of bowel may unmask previously undiagnosed gastrointestinal disease such as coeliac disease
  • hyperthyroidism - may cause paradoxic weight gain if it also causes congestive cardiac failure as in thyroid storm
  • it may be the start of chronic diarrhoea