All things diarrhoea (but not malabsorption)

Question 1

What is chronic diarrhoea?

Answer 1

Persistent diarrhoea for > 2 weeks

Question 2

What are the different types of diarrhoea?

Answer 2

Secretory

• Due to damaged intestinal epithelial cells
• Mainly due to bacterial toxins
• Stimulates Cl secretion and inhibits neutral copied NaCl absorption
• > 200ml/day
• Continues when enteral feeding is stopped
• Faecal Na > 90mosmol/L
• pH >6
• Reducing substances negative

Osmotic

• Presence of non-absorbed carbohydrate solutes gets fermented by colonic bacterial producing short-chain organic acids resulting in osmotic load
• Ceases when enteral feeding stopped
• Faecal pH < 5
• Faecal Na < 60mosmol/L
• Faecal osmo > 100 (290 - 2(Na+K)) - suggesting extra sugar load
• Reducing substances positive

Question 3

What is the acid-base disorder related to vomiting, esp with pyloric stenosis ?

Answer 3

Metabolic alkalosis with hypochloraemia and hypokalaemia

Gastric fluid

• main cation at rest: Na+
• main cation when stimulated: H+
• main anion: chloride

Loss of gastric fluid

• results in chloride and variable H+ loses
• causes metabolic alkalosis, initiated by loss of H+ then sustained by disproportionate loss of Cl- and the kidneys tried to reabsorb an anion (choosing HCO3)
• Loss of ECF –> activates renin-aldosterone system –> retains Na in exchange for K

Question 4

What is the acid-base disorder related to diarrhoea?

Answer 4

Only occurs when volume of fluid lost is large requiring the kidney’s ability to adjust excretion….

Typical presentation:

• Hypotension, acute renal failure
• Metabolic acidosis with hyperchloraemia and hypokalaemia

Long term laxative ingestion results in chronic loss of potassium so kidneys try to increase absorption of K in exchange of H+ –> metabolic alkalosis

Question 5

What are the differential diagnoses for acute diarrhoea?

Answer 5

Systemic infections:
- UTI, pneumonia, OM, meningitis, sepsis
Surgical
- Appendicitis, intussusception, malrotation, Hirschprung’s enterocolitis, partial bowel obstruction
Other
- DM, antibiotic-associated diarrhoea, primary disaccharide deficiency

Question 6

What are common causes of diarrhoea?

Answer 6

Viral

• rotavirus (winter) (dsRNA)
• norovirus (all seasons) (ssRNA)
• adenovirus 40, 41 (summer)
• astrovirus (winter)

Bacterial
- Campylobacter
Salmonella
EPEC / EAEC / EHEC

Protozoa

• Giardia
• Cryptosporidium

Question 7

What is lactase deficiency a complication of gastroenteritis?

Answer 7

Destruction of epithelial cells –> subvillous atrophy –> brush border enzymes deficiency (lactase is most superficial)

Question 8

What kinda vaccine is the rotateq?

Answer 8

Live attenuated vaccine

• reduces gastro of any severity by 70%
• reduces severe gastro by 85-100%
• reduces host by 50%

Question 9

What are complications of viral gastroenteritis?

Answer 9

Dehydration 
Febrile convulsions (rotavirus) 
Seizures from electrolyte imbalance 
Lactose intolerance 
- lasts 6-8wks

Question 10

Why do you need 1:1 sodium: glucose solution for rehydration?

Answer 10

Absorption of glucose is via glu-Na cotransporter….

Question 11

What are the causes of inflammatory enteritis?

Answer 11

Presents as fever, abode pain, abrupt onset of diarrhoea before vomiting, bloody / mucousy stools

Shigella, E.coli, Salmonella, Campylobacter, C.diff, entamoeba histolytic

Question 12

What are causes of secretory (enterotoxigenic) diarrhoea?

Answer 12

Stools are watery with no faecal leucocytes.

Toxigenic
- S aureus, B cereus, C perfringens

Enterotoxigenic
- E.Coli, giardia, cryptosporidium, rotavirus, norovirus

Question 13

What are the complications of shigella enteritis?

Answer 13

Gram -ve rod

Dehydration
Untreated illness is ~ 2 weeks
Abx can reduce course of illness / duration of pathogen excretion
Isolate untile diarrhoea settles

Rare

• Headache / meningism / seizures / encephalopathy
• HUS
• Septicaemia <5%
• Reiter syndrome (arthritis / urethritis / conjunctivitis)
• Hepatitis

Question 14

What are the special features that causes complications related to Salmonella infection?

Answer 14

Gram negative rod (bacilli) of the enterobacteriaceae family

Produces cholera-like endotoxin –> secretory diarrhoea
Also invades mucosa –> inflammatory response

Survives poorly in low pH conditions –> increased in those on PPI

Has special virulence factors to invade blood stream resulting in 1-5% bacteraemia
Risk factors: immunodeficiency (HIV: 50% mortality), < 3m old, sickle cell disease, IBD, malaria, schistosomiasis

Extra-intestinal disease

• Osteomyelitis
• Meningitis and brain abscess
• Endocarditis
• Reactive arthritis (HLAB27)

Cotrimoxazole / 3rd generation cephalosporin only indicated for <3/12, disseminated infection / severe or protracted course
(abx doesn’t shorten clinical course, in fact, may actually increase excretion time)

Question 15

What are the complications of campylobacter?

Answer 15

Gram -ve rod
9 species assoc with human disease - C. jejuni most common

Complications

• reactive arthritis (large migratory arthritis 5-40 days post)
• Guillain Barre syndrome (accounts for 25-40%)
• Reiters
• Ig A nephropathy

Antibiotics not beneficial…

Question 16

What are the complications with yersinia?

Answer 16

Gram negative coccobacilli

Siderophoric (iron loving)
Can present like appendicitis

Question 17

What are the complications with C.diff?

Answer 17

Spore-forming gram positive anaerobic rod (lives in soil)

Spectrum of severity
- from mild self-limited diarrhoea to pseudomembranitis colitis

Treatment

• Discontinue current abx
• rehydration
• Metronidazole or vancomycin

Question 18

Who is the mimic of coeliac disease?

Answer 18

Giardia

• protozoa (flagellate)
• lives in duodenum and upper jejunum
• causes symptoms of bloating / flatulence / intermittent diarrhoea / constipation / FTT / abdominal pain and cramps
• causes partial villous atrophy
• also releases cysts (faecal sample)
• treat with metronidazole