altered GI motility Flashcards
What are the lower GI motility symptoms?
Diarrhoea, constipation
what scoring system is used for describing faeces
bristol stool chart
What is the definition of diarrhoea?
Passage of loose or watery stools, typically at least 3 times a day in a 24hr period.
What are the features of diarrhoea? (2)
- Reduced consistency
- increased frequency
What is dysentery
Diarrhoea with visible blood or mucus - commonly have a fever and abdo pain
What time frame is acute diarrhoea?
<14 days
What time frame
is persistent diarrhoea
14-30 days
what time frame is chronic diarrhoea?
> 30 days
What is acute diarrhoea and what causes it (2)?
Increased water content of the stool - either due to impaired water absorption and/or active water secretion by
bowel
What causes acute diarrhoea? (3)
- INFECTIONS: [viral, bacterial, protozoal]
Rotovirus - kids
Norovirus - adults
Schistosomiasis - tropical infection - DRUGS (SE of many drugs)
- PSYCHOLOGICAL
What are the two types of chronic diarrhoea?
Osmotic and secretory diarrhoea
What is osmotic diarrhoea?
Water is drawn into in the bowel due to the presence of solutes within the lumen (natural osmosis), typically due to:
- Ingestion of a poorly absorbed solute
- Malabsorption
How can you reduce osmotic diarrhoea?
fasting
What are the causes of osmotic diarrhoea?(7)
- Carbohydrate malabsorption (e.g., lactose intolerance)
- Magnesium-induced (e.g., antacids)
- Osmotic laxatives (e.g., lactulose)
- Small intestinal mucosal disease (coeliac dx, severe
Crohn’s, enteritis etc.) - Reduced absorptive area (resection from e.g. Crohn’s)
- Bile acid malabsorption!!
- Pancreatic exocrine insufficiency (CF, pancreatic cancer - if it blocks pancreatic duct in the head of the pancreas,
chronic pancreatitis)
How does coeliac’s cause diarrhoea?
Stops you absorbing osmolytics - viliae atrophy so reduced absorptive area too
What does the pancreas do?
Endocrine and exocrine effects -> to help absorption of food, if it doesn’t work properly, then it will sit in the gut and it will pull water in
Where is bile produced and secreted?
Liver produces and secreted by the bile duct
Where does the secreted bile go?
Into the duodenum where 95% is then absorbed in the terminal ileum and only 5% is excreted
What does the gallbladder do?
Stores bile until fat needs digesting, then the gallbladder is squeezed and bile goes into the duodenum to help the fat be digested
What is bile acid diarrhoea?
Bile isn’t absorbed (e.g. due to resection of the terminal ileum) and so sits in the gut and draws water in to the gut
What is lactulose?
Syrup/sugar drink -> non-absorbable sugar that sits in the gut and drags water in (osmotic laxative)
What is lactose intolerance?
a form of carbohydrate malabsorption - We need lactase in our body to break down milk as babies, and when we get older, the amount of lactase reduces;
More prominent in the East
What is secretory diarrhoea
Actively increased secretion of fluid and electrolytes
What can cause secretory diarrhoea? (6)
- Bacterial endotoxins (E.coli, cholera, c.diff) -> irritates bowel causing secretions
- Stimulant laxatives (senna)
- Hormones (hyperthyroidism)
- Bile acid malabsorption
- Mucosal inflammation (Ulcerative coliits, Crohn’s)
- Rectal villous adenoma (an adenoma with villi-like protrusions that means it is less likely for secretions to be absorbed)
what is rectal villous adenoma
a precancerous secretatory polyp which => the polyps are covered in mucous -> secretes lots of fluid, distal lesion - the body cannot resorb it all)
What are the different types of adenoma histologically?
- Tubulous
- villous
- tubular-villous
How is diarrhoea treated?
- Treat underlying disorder
- Opiates
- Anti-secretory drugs (octreotide - somatostatin analogue)
How do opiates work to treat diarrhoea?
decrease urgency, bowel frequency and stool volume
e.g. loperamide - immodium (+ codeine but more SEs)
Why would you not give loperamide (opioid) with
IBD
risk of toxic megacolon development
erosion vs ulcer (GI)
Erosion - superficial/partial break within the epithelium or mucosal surface;
Ulcer - deep break through the full thickness of the epithelium or mucosal surface.
why does bowel resection result in osmotic diahhorea
reduced absoptive area leads to decreased ability to absorb nutrient => higher osmotic gradient -> more water moves into the bowel lumen
why does a Cholecystectomy result in osmotic diahorrea
removal of gall bladder means that bile is just being continuously released -> resorptive capacity in the terminal ileum overwhelmed -> more bile in the colon which has an osmotic effect
What are the 2 main types of
constipation?
- Slow colon transit constipation
- impaired rectal emptying
(3. both)
How can you differentiate between a defecatory disorder and a slow transit defaecation
Shapes study:
Pt ingests radiopaque markers (plastic rings containing radiopaque material) in a meal and abdo XRs are obtained to monitor clearance of the rings from the colon ->
Normal colonic transit time = 20-56 hours, and most adults will clear all the markers in 4-5 days and <20% of the original rings at 5 days = normal
What’s constipation?
opening bowels less than 3 times a week
What are the causes of constipation? (7)
- Endocrine (hypothyroidism)
- Metabolic (hypercalcaemia / hypokalaemia / hypomagnesiumia)
- Neurological (PD, MS)
- Neuromuscular (MND, MG)
- Psychological (brain-gut axis - anxiety)
- Physiological (dehydration)
- Mechanical (obstruction - malignancy - annular applecore lesion on barium, stricture from chronic IBD)
[+ drugs - opioids, imodium]
How can we generally manage
constipation?
- Identify any anatomical abnormalities
- Identify biochemcial causes
- Stop constipating drugs
- Exercise
- Increase fluid intake
- Increase dietary fibre (SEs - bloating, flatulence)
constipation mgx + examples (5)
- Bulk forming laxatives - ispaghula, sterculia (used for mild constipation) - improves bowel frequency
- Stimulant laxatives - senna, bisacodyl, sodium picosulphate - increases motility, frequency and improves consistency BUT risk of atonic colon (it just stops
working) - Stool softeners - liquid paraffin, sodium docusate, arachic oil enema (BUT contains peanut oil) - limited efficacy but
widely used - Osmotic laxatives - lactulose, magnesium salts (main SE: hypermagnesaemia)
- Prucalopride (for IBS-C) - use for constipation is after 6
months of trying 2 different laxatives. If no benefit, try:
- Lubiprostone
- Linaclotide
bulk forming laxatives MOA
absorb liquid in the intestines and swell to form a soft, bulky stool -> The bowel is then stimulated normally by the presence of the bulky mass
stimulant laxatives MOA
cause peristalsis by stimulating colonic nerves (senna) or colonic and rectal nerves (bisacodyl, sodium picosulfate) -> parasympathetic stimulation
what can be given if a pt is experiencing opioid induced constipation and why
Naloxegol - only used once constipation not adequately responded to laxatives ->
It only works in the gut but not elsewhere so it won’t reverse the pain-relief effects elsewhere
How does lactulose work and what are 2 side effects
Osmotic laxative - Decreases colonic pH by generation of fatty acids and fermentation products, causing water to go by osmosis into the gut
SEs: Bloating, flatulence
What can happen with chronic senna ingestion
melanosis coli - Deposition of darker pigment -> can see reticulated striations (alligator skin), looks like shadow of water moving in a pool
What is the difference between
IBS-C and functional constipation?
IBS - Must have pain to have IBS and pain improves after bowel movement usually
Functional - no pain necessarily
