Diarrhoea Flashcards
Diarrhoea definition? Passage of…
- three or more loose or liquid stools per 24 hours, and/or
- stools that are more frequent than what is normal for the individual lasting <14, and/or
- stool weight greater than 200 g/day
decreased absorption or increased secretion of fluid and electrolytes, or increase in bowel motility
Diarrhoea duration classification?
- acute (<14 days)
- persistent (>14 days)
- chronic (>4 weeks)
How much fluid enters GI tract every day?
10 litres
What is the major site for re-absorption?
Small intestine
How much fluid is reabsorbed?
About 99% reabsorbed
0.1 litre excreted in faeces
Inflammatory diarrhoea causes?
Can be due to bacterial, viral, or parasitic infection
May develop early in course of bowel ischaemia, radiation injury, or inflammatory bowel disease
Inflammatory diarrhoea associated symptoms?
Mucoid and bloody stool
Tenesmus
Fever
Severe cramps abdominal pain
Infectious inflammatory diarrhoea? Volume and bowel movements
Small volume
Frequent bowel movements
does not usually result in volume depletion in adults
Most common bacterial causes of infectious diarrhoea? In US
Campylobacter
Salmonella
Shigella
E. coli
Clostridium difficule
Other causes of infectious diarrhoea?
Viruses (more common among children who attend day care centres)
Protozoa and parasites (common causes of acute diarrhoea in developing countries)
Examination of stool in inflammatory diarrhoea?
May show leukocytes
Tests for occult blood may be positive
Faecal calprotectin
test for faecal leukocytes - plagued by high rate of false-negatives but positive test very informative
Histology of GI tract in inflammatory diarrhoea?
Abnormal
Non-inflammatory diarrhoea? Volume, frequency and symptoms compared to inflammatory
Watery, large-volume, frequent stool (>10 to 20 per day)
volume depletion is possible due to high volume and frequency of bowel movements
no tenesmus, blood in stool, fever, or faecal leukocytes
Histology of GI tract in non-inflammatory diarrhoea?
Preserved
Non-inflammatory diarrhoea subdivisions?
Secretory diarrhoea
Osmotic diarrhoea
Secretory diarrhoea? Mechanism and osmotic gap
Altered transport of ions across mucosa -> increased secretion and decreased absorption of fluids and electrolytes from GI tract (esp. small intestine)
doesn’t decrease by fasting
low stool osmotic gap
Causes of secretory diarrhoea?
Enterotoxins
Hormonal agents
Laxative use, intestinal resection, bile salts, fatty acids
also seen in chronic diarrhoea with coeliac sprue, collagenous colitis, hyperthyroidism, and carcinoid tumours
Enterotoxin causes of secretory diarrhoea?
Vibrio cholera
Staph. a
Enterotoxigenic E. coli
Possibly HIV and rotavirus
Hormonal causes of secretory diarrhoea?
Vaso-activate intestinal peptide
Small-cell cancer of the lung
Neuroblastoma
Osmotic diarrhoea? Volume and mechanism
Stool volume relatively small, diarrhoea improves with fasting
Results from presence of unabsorbed solute (magnesium, sorbitol, mannitol) in intestinal tract that causes increased secretion of liquids into gut lumen
Osmotic diarrhoea tests and osmotic gap?
Stool electrolytes shows increased osmotic gap (>50)
Stool is always isosmotic (260-290 mOsm/L)
so stool osmotic gap test could differentiate between osmotic and secretory diarrhoea
high stool osmotic gap
Osmotic diarrhoea subdivisions?
Maldigestion
Malabsorption
Transcellular vs paracellular transport?
Transcellular transport - when solutes travel through the cell
Paracellular transport - when solutes travel around the cell (e.g. through gap junctions)
Water secretion into lumen?
- Chloride channels on luminal side activated, chroride ions transported into cellular lumen
- Causes paracellular transport of sodium from interstitial space -> lumen
- This creates osmotic gradient - water follows the solute so water is secreted into the lumen
Water absorption?
Sodium transporters on luminal and interstitial side cause transcellular sodium transport into capillaries - water follows into capillaries (through enterocytes)
often on empty stomach
How does infection cause inflammatory diarrhoea?
Reduced absorption
Pathogens affect interstitial lining -> affects transport and reduces water absorption
causes water retention in lumen -> diarrhoea
Secretory diarrhoea? Mechanism and 2 causes
Increased secretion
increased activation of chloride transporters -> increased secretion of water into lumen -> diarrhoea
Causes - cholera toxin, laxatives…
How does lactose intolerance cause maldigestion diarrhoea (osmotic)
Lactose not being digested into glucose (and galactose) so process of sodium absorption and water absorption does not happen
How does pancreatic exocrine insufficiency cause maldigestion diarrhoea (osmotic)?
Problem with digestive enzymes - insufficient digestion of food -> sodium transporters or enterocytes not activated -> reduces transport + absorption of sodium -> reduced absorption of water and diarrhoea
Malabsorption diarrhoea causes?
Sorbitol (found in proons)
Surgical resection
Bacterial overgrowth
causes water retention in lumen
Reduced absorption causes of diarrhoea?
Inflammatory diarrhoea
Osmotic diarrhoea - maldigestion and malabsorption
Cause of increased secretion diarrhoea?
Secretory diarrhoea
Conjugates on drugs?
Drugs with large conjugates attached to them which can be digested in specific place e.g. colon - would be helpful if inflammation in colon
Drugs to improve absorption in small intestine considerations and side effects?
Small intestine structures allow for maximal absorption, leading to high systemic availability of any absorbed medication
causes increased side effect profile of medications due to enhanced absorption
Anti-inflammatory drugs problem?
Anti-inflammatory drugs are designed for colon absorption, so only effective if inflammation causing diarrhoea originates in colon
tend to be potent drugs with significant side effects
Targeting transporters for secretory diarrhoea?
Intestinal transporters implicated in diarrhoea process, e.g. SGLT-2, sodium channels, sodium-glucose transporter
Targets are expressed throughout the body (causing potential side effects)
aim is to reduce secretion and/or to increase absorption
Maldigestion drugs difficulty and strategies?
Difficult to enhance endogenous enzyme activity
Exogenous enzymes are susceptible to digestive process
Strategies - enteric coating, probiotics, gene therapy
Gene therapy risks?
Unwanted immune response, incorrect cell targeting
IBS symptoms?
Alternating constipation and diarrhoea
Bloating
Abdominal pain
Faecal urgency
Mucus in stool
Fatigue
IBD symptoms?
Weight loss
Fever
Blood in stool
raised faecal calprotectin unlike in IBS
Abdominal pain
Faecal urgency
Mucus in stool
Fatigue
IBS and IBD shared symptoms?
Abdominal pain
Faecal urgency
Mucus in stool
Fatigue
Organic cause of diarrhoea investigations?
- FBC - check for amaemia and signs of inflammation, LFT, pancreatic enzymes, TSH, ESR (acute inflammation), CA-125 (ovarian cancer)
- Urea and electrolytes - check renal function and electrolyte status
- CRP - look for signs of infection/inflammation
- Stool MC&S (for infective), qFIT (microscopic blood in stool), faecal calprotectin (inflammation in bowel)
- X-ray, colonoscopy
Stool tests for organic diarrhoea?
Stool tests - routine microbiology, ova cysts and parasites (3 specimens a min of 2 days apart as ova and cysts are shed intermittently), calprotectin
Blood tests for diarrhoea?
FBC, U&E, LFTs, Ca2+, B12, folate, ferritin, TFTs, ESR/CRP, test for coeliac
Faecal calprotectin if bloods show abnormality
Types of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
Features of Crohn’s vs ulcerative colitis? Lesions and layers
Crohn’s - Non-continuous lesions or “skip lesions” in Crohn’s, cobblestone appearance. Affects all layers of bowel
UC - Continuous and uniform, no breaks of normal bowel. Affects mucosa (and submucosa) only
Location of Crohn’s vs ulcerative colitis?
Crohn’s - anywhere, mouth to anus in skip lesions (commonly starts at terminal ileum)
UC - primarily affects colon and rectum, usually starts in rectum then spreads upwards. Only affects large bowel
Depth of inflammation in Crohn’s vs ulcerative colitis?
Crohn’s - transmural involvement, affects all layers of intestinal wall
UC - just mucosa, continuous inflammation
Granulomas in Crohn’s vs ulcerative colitis?
More common in Crohn’s (non-caseating and increased goblet cells)
Could be due to more macrophages in Crohn’s, compared to more neutrophils in UC which have a shorter half life
Crypt abscesses in Crohn’s vs ulcerative colitis?
More common in Crohn’s
crypt distortion without branching in UC
Ulcerations and fistulas in Crohn’s vs ulcerative colitis?
Crohn’s - fistulas and deep ulcerations may be present, perianal area fistulas or skin tags, more likely perianal involvement
UC - superficial ulcerations without fistulas, broad-based ulcers and pseudopolyps common
Conservative management for Crohn’s disease?
Lifestyle (smoking cessation, avoiding foods that trigger flare ups so dietary modification)
reducing fibre
High calorie supplements
Medical management to induce remission of Crohn’s?
Steroids (oral - prednisolone, IV - hydrocortisone) for a flare up
Aminosalicylate
Azathioprine/mercaptopurine
Infliximab/adalimumab
Medical management to maintain remission of Crohn’s?
Immunosuppressants
- Azathioprine/mercaptopurine
- Methotrexate
Surgical management of Crohn’s?
Bowel resection
Main symptoms of Crohn’s?
Diarrhoea
Stomach aches and cramps
Blood in poo
Tiredness
Weight loss
high temp, nausea and vomiting, joint pains, sore and red eyes, patches of painful, red, swollen skin, mouth ulcers
Causes of Crohn’s?
Genes
Autoimmune
Smoking
Previous stomach bug
Abnormal balance of gut bacteria
Specialist tests for Crohn’s?
Colonoscopy
Biopsy
MRI or CT
Treatment for Crohn’s? (NHS website)
Steroids
Liquid diet
Immunosuppressants
Biological medicines
Surgery
Living with Crohn’s? (NHS website)
ibuprofen can make it worse
Vaccinations should be taken
Tell GP about pregnancy
Contraception may not work the same (OCP)
Cancer screening - BOWEL CANCER
Normal stool osmotic gap values?
Between 50 and 100
Smoking in Crohn’s vs UC?
Smoking risk factor for Crohn’s
Smoking protective against UC
Only diagnostic investigations for IBD?
Colonoscopy and biopsy
Corticosteroid example for Crohn’s?
Prednisolone
Immunosuppressants for Crohn’s?
- Azathioprine
- Mercaptopurine
- Methotrexate
Biologics for Crohn’s?
- Adalimumab
- Infliximab
Lifestyle precautions for Crohn’s? Diet, medication, recommended, avoid
Diet - enteral nutrition for children, healthy for adults, stop smoking
Medication - NSAIDs can interact with Crohn’s medication
Recommended - flu and pneumococcal jab
AVOID - live vaccines
Maldigestion diarrhoea mechanism and 2 causes?
Impaired digestion of nutrients within intestinal lumen or brush border membrane of mucosal epithelial cells.
In pancreatic exocrine insufficiency and lactase deficiency.
Malabsorption diarrhoea? Mechanism and some causes
Impaired absorption of nutrients
In small bowel bacterial overgrowth, mesenteric ischaemia, post bowel resection, mucosal disease (coeliac)
