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Diarrhoea in adults

Generally defined as passing loose watery stools at least 3 times a day
Best defined in terms of
○ frequency
○ consistency
○ volume or weight
Consistency is determined by water holding capacity of the stool ( amount of non-bound free water ) and this possibly best defines the concept of diarrhoea

Stool weight > 200 g/D- often regarded as Upper Limit of normal Other terms often associated / used 
○ Frequency – relates to number of stools passed
○ Urgency – sensation of need to defecate without delay
○ Incontinence ( faecal ) uncontrolled passage of solid or liquid faeces at socially inappropriate time and places
○ Faecal impaction or loading- when rectum & often lower colon is full with hard or soft stool –> can lead to overflow diarrhea
How commmonNoravirus is associated with approximately 1/5th of all infectious
 diarrhoea cases ( adults & children ) Incidence of rotavirus has reduced due to vaccination Chronic diarrhoea is often caused by inflammatory
 bowel disease ( Crohn’s and Ulcerative colitis ) Acute diarrhoeal infection is a leading cause of hospitalization, out-patient visits and lost quality of life ( both in domestic setting & those who are travelling) Most commonly isolated pathogen ( acute diarrhoea ) include noravirus , sapovirus , Campylobacter spp and rotavirus ) In the USA management of acute diarrhoea costs $ 150 million upwards to the healthcare economy
Osmotic diarrhoea
○ soluble compound cannot be absorbed by the small intestine –> draws fluid into intestinal lumen
○ eg ingestion of non-absorbable substance as a laxative like Mg sulphate or Mg containing antacid
○ generalized malabsorption eg coeliac disease and pancreatic insufficiency
○ consuming large quantities of artificial sweeteners as sorbitol
 Secretory diarrhoea
○ both active intestinal secretions of fluid and electrolytes as well as decreased absorption
○ net fluid loss
○ Enterotoxins –> cholera , E.coli , C.difficile
○ Neurohormonal agents eg VIP , bile salts 
○ laxatives as docusate

Secretory diarrhoea continues on fasting
 Inflammatory diarrhoea- damage to intestinal mucosal cells–> loss of fluid
 and blood + defective absorption of fluid and electrolytes- eg include
○ infective causes as shigella
○ inflammatory conditions as ulcerative collitis , Crohn’s , coeliac 
 Abnormal gut motility – eg diabetic and hyperthyroid diarrhoea
Acute diarrhoeaMost acute episodes are infectious- look for supporting information as
○ fever
○ recent contact with a person with diarrhoea
○ exposure to possible source
 ♦ meals outside , takeaways
 ♦ farm visit , camping
○ travel history
 Drug related- new drugs particularly antibiotics Stress and anxiety Abdominal symptoms – eg marked tenderness 
? appendicitis Radiation treatment CV dis or hypercoagulable 
state –> risk intestinal ischaemia

Red flags –Blood in stool Recent hospital admission or antibiotic Rx- consider antibiotic associated diarrhoea Persistent vomiting Weight loss Painless , watery , high volume diarrhoea ↑↑ risk dehydration Nocturnal symptoms disturbing sleep ↑↑ risk organic cause
Consider admission –Risk dehydration or shock- vomiting and unable to retain fluids Age ( people < 60 ↑ risk of complications ) Fever Bloody diarrhoea Abdominal symptoms as pain and tenderness Co-morbidities as
○ immunodeficiency
○ lack of stomach acid
○ inflammatory bowel disease
○ valvular heart disease
○ diabetes mellitus
○ renal impairment
○ rheumatoid disease , SLE
○ drugs as immunosuppresants or systemic steroids , PPIs ,ACE , diuretics
Check stool sample-Systemically unwell- needs hospital admission and or antibiotics Blood or pus in stool Immunocompromised state Recent antibiotics use or hospital admission
○ request specifically for Clostridium difficile History of foreign travel- ask for ova , cysts and parasites Diarrhoe > 2 weeks and Giardia is suspected Reassurance
Consider public health advice –Suspected public health hazard
○ diarrhoea in food handlers , health-care workers , elderly residents in care homes Outbreak in community or family Contacts of people infected with organisms as E.coli 0157:H7 ( may have serious clinical sequeale )
Chronic diarrhea causesColonic
○ colonic neoplasia
○ UC and Crohn’s
○ microscopic colitis (watery nocturnal diarrhoea in older ♀ often associated with coeliac disease )
 Small bowel
○ Coeliac disease
○ Crohn’s
○ other small bowel enteropathies as
 ♦ Whipple’s ♦ Tropical sprue ♦ Amyloid
 ♦ Intestinal lymphangiectasia
○ Bile acid malabsorption
○ Disaccharide deiciency
○ Small bowel bacterial overgrowth
○ Mesenteric ischaemia
○ Radiation enteritis
○ Lymphoma
○ Giardiasis ( & other chronic infections )
○ Chronic pancreatitis
○ Pancreatic carcinoma
○ Cystic fibrosis
○ Hyperthyroidism
○ Diabetes
○ Hypoparathyroidism
○ Addison’s disease
○ Hormone secreting tumours
 ♦ VIPoma ♦ gastrinoma ♦ carcinoid
○ Factitious diarrhoea ( laxative use )
○ surgical causes- eg small bowel resection , internal fistulae
○ Drugs
○ Alcohol
○ Autonomic neuropathy
investigations –FBC- anaemia or ↑ platelet count ( inflammation ) LFT Tests for malabsorption
○ Calcium
○ Vit B12 and red cell folate
○ Ferritin TFT ESR and CRP Coeliac screen Stool sample
○ culture and sensitivity
○ ova cysts and parasites
Three specimens 2-3 days apart
○ consider checking for C.difficile
Medications –Allopurinol ARB’s Antibiotics Digoxin Colchicine Cytotoxic drugs ( eg chemotherapy , methotrexate ) H-2 receptor antagonists Laxatives Magnesium- containing antacids Metformin NSAIDs NSAID’s PPI’s SSRI’s Statins Theophylline Thyroxine High dose vitamin C
Symptoms suggestive of Colorectal cancer Age 40 + or older
○ rectal bleeding with a CIBH towards loose stools and/ or
○ ↑ stool frequency persisting 6 weeks or more Right lower abdominal mass – consistent with involvement of large bowel Palpable rectal mass Aged 60 or over with
○ CIBH to looser stools and/ or ↑ frequent stools persisting for 6 weeks or more with ot without rectal bleeding Men of any age with unexplained iron deficiency anemia and a Hb of 11 or less Non menstruating ♀ with unexplained iron deficiency anemia and a Hb of 10 or less


Diarrhoea information from NHS Inform Scot
Travellers diarrhoea from Fit for Travel a very useful resource
Norovirus patient information leaflet from Buckinghamshire Healthcare NHS Trust
Sothercross Medical Library on diarrhoea
Clostridium difficile –PIL
Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition Ramesh P Arasaradnam1,2,3, Steven Brown4, Alastair Forbes5, Mark R Fox6,7Pali Hungin8Lawrence Kelman9Giles Major10Michelle O’Connor9, Dave S Sanders4Rakesh Sinha11Stephen Charles Smith12Paul Thomas13Julian R F Walters14

A great learning resource from United European Gastroenterology – Mistakes in chronic diarrhoea and how to avoid them
PERSPECTIVES IN CLINICAL GASTROENTEROLOGY AND HEPATOLOGY Chronic Diarrhea: Diagnosis and Management Lawrence R. Schiller,* Darrell S. Pardi,‡ and Joseph H. Sellin§ *Department of Internal Medicine, Division of Gastroenterology, Baylor University Medical Center, Dallas, Texas; ‡ Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota; and § Department of Medicine, Section of Gastroenterology and Hepatology, Baylor College of Medicine, Houston, Texas
AGA ( American Gastroenterology Association ) Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D) Smalley, Walter et al. Gastroenterology, Volume 157, Issue 3, 851 – 854


  1. Investigating young adults with chronic diarrhoea in primary care BMJ 2015;350:h573
  2. Colorectal adenocarcinoma : risks , prevention and diagnosis BMJ 2016;354:i3590
  3. Guidelines for the investigations of chronic diarrhoea, 2nd edition Gut 2003;52(Suppl V):v1-v15
  4. The management for diarrhoea in adults Royal College of Nursing May 2013
  5. Diarrhoea- adult’s assessment CKS NHS March 2013
  6. Diarrhoea & Constipation Crohn’s and Colitis UK April 2016
  7. Chronic Diarrhoea : Diagnosis and Management Medscape
  8. Clinical Gastroenterology and Hepatology.2017;15(2);182-193
  9. Management of suspected infectious diarrhoea by English GPs : are they right ? Br J Gen Pract 2014;64 (618): e24-e30
  10. NICE Urgent Suspected Cancer Recognition and Referral
  11. WGO Practice Guideline -Acute Diarrhoea Nemeth V, Zulfiqar H, Pfleghaar N.
  12. Diarrhea. [Updated 2019 Jun 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.Available from:


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