Diarrhoea

Question 1

DIARRHOEA

Answer 1

• Organic causes (Stool weight >150g/day) has to be distinguished from Functional causes
• Bowel Frequency associated with Crampy Abdominal Pains, Fever suggest Infective Diarrhoea;
Bowel frequency with Loose Blood-stained Stool suggests Inflammatory causes; Pale stools
that float accompanied with Anorexia and Weight loss suggests Steatorrhoea

• Nocturnal bowel frequency and urgency suggests Organic causes; Passage of frequent small-
volume stools suggests Functional causes

Question 2

Osmotic Diarrhoea

Answer 2

Fluid enters the bowel if large quantities of non-absorbed hypertonic
substances are present in the lumen
o Ingestion of Non-absorbable substances (e.g. Magnesium Antacids), Generalised or
Specific malabsorption leaving high concentrations of solute in lumen
o Volume of diarrhoea reduced by absorption in Ileum and Colon; Diarrhoea stops
when patient stops eating or malabsorptive substance discontinued

Question 3

Secretory Diarrhoea

Answer 3

Active Intestinal secretion of Fluid/Electrolytes and ↓Absorption
o Enterotoxins (Cholera, E coli, C difficile), Hormones (VIP in Verner-Morrison
Syndrome), Bile salts and Fatty acids (Following Ileal Resection) and some laxatives
(Docusate Sodium)

Question 4

Inflammatory Diarrhoea

Answer 4

Mucosal destruction leads to loss of Fluid and Blood and Defect in
Fluid and Electrolyte absorption
o Infective (Shigella Dysentery) and Inflammatory conditions (e.g. IBD)

Question 5

Abnormal Motility

Answer 5

Diabetic, Post-Vagotomy, Hyperthyroidism; Symptoms exacerbated by
Small Bowel Bacterial Overgrowth

Question 6

ACUTE DIARRHOEA

Answer 6

• Very common, often Short-lived; Requires no
Investigations or Treatment; Viral Diarrhoea may
last 24-48hrs; Traveller’s Diarrhoea usually lasts 2-5
days; Viral and Bacterial Infective Diarrhoeas do not
last more than 2 weeks
• May be associated with Fever, Abdominal Pain,
Vomiting; Dehydration may be a problem if severe,
especially in extremes of age
• Stool sample if systemically unwell, requires
admission, or antibiotics; If there is blood/purulent
stool, Immunocompromised or received Antibiotics
(?C diff infection)
o Request Ova, Cysts and Parasites if
Diarrhoea after foreign travel
o Sample (1ml minimum) for MC+S; If
Recurrent and Parasites suspected, 3 × 5ml
samples 2-3 days apart to increase
likelihood of detection

• Inform Local Health Protection if – Suspected PH
Hazard (E.g. Food handlers, Healthcare Workers,
Elderly residents in care homes), Outbreaks within
Family or Community, or specific organisms (E.g. E
coli O157:H7)
• Admission if Vomiting and unable to retain fluid, or
features of Severe Dehydration/Shock
o Weakness, Confusion, Shock, Tachycardia, Marked Peripheral Vasoconstriction,
SBP<90mmHg, Oliguria or Anuria

Question 7

Toxigenic Food Poisoning

Answer 7

• Pre-formed Toxins in food
• No Invasion or Proliferation
• Incubation minutes to hours
• S aureus, B cereus, C perfringens

Question 8

Foodborne Infection

Answer 8

• Active Infective Agent; Invasion and
Proliferation within GI Tract
• Incubation hours to days
• Campylobacter, Salmonella, Coliforms,

Viruses (e.g. Norovirus)
• NB: organisms also produce toxins, but
tends to occur upon entry to GI tract

Question 9

Chronic Diarrhoea

Answer 9

• Steatorrhoea suggests Small Bowel disease, Watery/Loose Diarrhoea suggests Colonic lesions;
Bloody diarrhoea has to be investigated for Inflammatory Bowel Disease and Carcinoma
• Colonoscopy necessary if Cultures are negative and Small Bowel Disease is not suspected

Question 10

C difficile Associated Diarrhoea

Answer 10

• Can lead to Pseudomembranous Colitis (caused by Clostridium
difficile) may develop following antibiotic use (Especially Co-Amox or Clindamycin); May occur the first few days after to up to
6 weeks after stopped drug

Question 11

Bile Acid Malabsorption

Answer 11

• Underdiagnosed cause of Chronic Diarrhoea; Increased concentration of Bile Acids in Colon
leads to reduced reabsorption of water, causing diarrhoea; At higher concentrations, Bile
Acids also increase secretion and increase Colon motility
• Considered in patients with Chronic Diarrhoea of unknown cause and also IBD patients not
responding to standard therapy
• Diagnosis made by SeHCAT Test – Radiolabelled Bile Acid Analogues administered;
Percentage retention at 7 days calculated (<19% retention is abnormal)
• Treated with Bile Acid Sequestrants (e.g. Cholestyramine) which are resins that bind and
inactivate action of Bile Acids in Colon

Question 12

Gastrointestinal Problems in AIDS Patients

Answer 12

• Dysphagia, Oral Ulceration – HSV, CMV, Candidiasis
• Chronic Diarrhoea, Steatorrhea, Weight Loss – Parasitic Infections (E.g. Entamoeba, Giardia,
Cryptosporidium), Viruses, Bacterial (E.g. Salmonella, Campylobacter, MAIC);
o Can also occur as part of Neoplastic Disease (Kaposi’s Sarcoma, Lymphoma) and
Disseminated Infections (MAIC), or consequence of Anti-Retroviral Therapy