GIT Flashcards
Define acute diarrhea
Passage ≥ 3 loose stools per day for <2 weeks
Define chronic diarrhea
> 4 weeks
Name 3 indications for lab evaluation of diarrhoea.
• Severe with fever
• prolonged >14 days
• dysentery - contain blood / mucus
Which investigations are done for chronic secretory diarrhoea (5)
Exclude bacterial/parasitic infection
• gastrin
• metanephrine
• tsh
• test for bacterial overgrowth only inselected patients
Which investigations are done for chronic osmotic diarrhoea (3)
• Usually without steatorrhea due to poorly absorbable CHO or mg salts
• Suspected lactose intolerance: hydrogen breath test / measure lactose in mucosal biopsy
• sorbitol or fructose ingestion
Name 7 malabsorption causes of diarrhoea, steatorrhea
•Pancreatic enzyme deficiency eg chronic pancreatitis, cystic fibrosis
• bile salts deficiency biliary obstruction and hepatic disease
• coeliac disease
. IBD
• drugs: laxatives, magnesium salts
• Endocrine: thyrotoxicosis, carcinoid syndrome, vipoma
• lactase deficiency - lactose intolerance
Name 3 lab tests for chronic diarrhoea
• Faecal na, k to calculate osmotic gap
>125 = osmotic diarrhoea
<50 = secretory diarrhoea
• faecal ph
< 5,6 = carbohydrate malabsorption
• faecal laxative screening: magnesium, phenolphthalein
How calculate osmotic gap
290 - 2 (na +k)
How further evaluate chronic inflammatory diarrhoea? (2)
• Small bowel follow through and sigmoidoscopy or colonoscopy with biopsies for IBD
• stool culture, ID infectious causes inflammation
How further evaluate chronic fatty diarrhoea? (2)
• Assess pancreatic exocrine function by fecal elastase! (Good sensitivity,)
• small bowel biopsy and aspirate of contents for culture
How further evaluate carbohydrate malabsorption diarrhoea? (2)
• Hydrogen breath tests (measured in exhale while fasting and after sugar - bacterial overgrowth, carbohydrate malabsorption)
• d-xylose absorption test (differentiate between mucosal disease which will have decreased absorption, and pancreatic disease)
How diagnose h pylori?
Urea breath test best.
(Can also do stool antigen by immunoassay)
What is zollinger Ellison syndrome
Gastrinoma → increased acid secretion
20% also have parathyroid and pituitary adenoma as part of
Men 1
Diagnosis zollinger Ellison syndrome
• Raised basal acid output (bao)>15 and raised serum gastrin
• exclude h pylori and pernicious anaemia, they also cause high gastrin
What is coeliac disease
Sensitive to gliadin in gluten
Diagnosis coeliac disease? (4)
• Serology while on gluten diet
. Antibodies: IgA ema (endomysial antibody), IgA tTG (tissue transglutaminase antibody)
. In selective IgA deficiency, do igG ttg or EMA
• At least 3 duodenal biopsies to confirm diagnosis
IBD diagnosis? (2)
• Fecal calprotectin!
• fecal alpha 1 antitrypsin
Define secretory diarrhea and examples
- Luminal ion channels disrupted → increased secretion or decreased absorption of ions. → water follows ions.
- No structural damage
- example: mostly infections. cholera → Cl secretion → sodium and water follows; rotavirus; C diff; carcinoid; gastronoma; VIP Oma
Define osmotic diarrhea and examples
- Aka malabsorption.
- increased osmole eg sugar, salt, fat, artificial sweetener draws too much water into bowels
- eg lactase deficiency, celiac/tropical sprue, Whipple’s disease, pancreatic insufficiency, consuming sugar free food drink/gum
Define inflammatory diarrhea and examples
Damage to mucosal lining and /or brush border
(Exudative = oozing blood, mucous, pus, plasma protein into stool)
Eg: IBD, some infections, ischaemic colitis, diverticulitis, radiation colitis
How diagnose secretary diarrhea
- Fecal Osmolar gap < 50
- no fecal fat. No stool. No fat /blood/wbc
How diagnose osmotic diarrhea (2)
- Stool osmolar gap > 125
- goes away with npo
- can have faecal fat
How diagnose inflammatory diarrhea (4)
- Blood
- WBC
- mucous in stool
- do colonoscopy
What is calprotectin and what does it indicate
- Ca binding protein found in cytosol of neutrophils
- resistant to bacterial degradation, stable in stool for 5 days following excretion
- thus raised calprotectin = increased neutrophils in git = indicates inflammation
- Do colonoscopy for these patients - likely IBD (not ibs- this is how differentiate )
