diarrhoea Flashcards
causes of diarrhoea
viral/bacterial infection
drugs
IBS/IBD
4 types of diarrhoea
osmotic
secretory
chronic and inflammatory
dysfunctional
What is osmotic diarrhoea caused by?
decreased absorption or increased secretion of water and electrolytes by intestinal epithelium
too much water into bowel
main causes of osmotic diarrhoea
bacterial enterotoxins (cholera, E. Coli)
luminal secreting agents (bile acids, laxatives)
circulating secreting agents (hormones, drugs, poisons)
medical problems (Addison’s disease, carcinoid tumour, vipoma)
What malabsorption syndromes is osmotic diarrhoea common in?
lactose intolerance
Celiac disease
How to distinguish between osmotic and secretory diarrhoea?
calculating the fecal osmotic gap
What is the stool osmotic gap?
difference between Na and K ions in the stool
What is normal osmolarity?
50 - 100 mOsm/kg
What osmolarity indicated secretory diarrhoea?
< 50 mOsm/kg
osmolarity for osmotic diarrhoea?
> 100 mOsm/kg
secretory/osmotic affected by fasting?
osmotic decreases in severity with fasting
osmotic load removed
What causes chronic/inflammatory diarrhoea?
inflammation in the bowel mucosa causes decreased fluid resorption
inflammatory diarrhoea in what diseases?
CD
UC
intestinal infections - clostridiodies difficile or shigella
What’s in stool in inflammatory diarrhoea?
blood
WBCs
mucous
What is functional diarrhoea?
chronic or recurrent diarrhoea not explained by structural or biochemical abnormalaties
most common functional diarrhoea
IBS
What could be a cause of functional diarrhoea?
alterations in microbiome of intestine and rapid transit time of contents through GIT
cause of diarrhoea due to impaired intestinal motility
abnormal intestinal motility where transit time is accelerated and absorption is decreased
exudative diarrhoea?
caused by drugs that cause imflammation and ulceration in the intestine
microscopic colitis cause of diarrhoea
drugs cause thick submucosal band of collagen in intestine
results in watery diarrhoea
Most common cause in adults?
campylobacter
most common cause in children?
rotavirus
Most common cause of travellers diarrhoea?
enterotoxigenic E coli
how long until symptoms?
72 hours
What indicates bacterial toxins are being produced?
onset of 6 hours after meal
How long does it last?
short duration
4 - 7 days
When to refer?
>72hrs healthy adult >48hrs elderly >24hrs diabetics severe vomiting and fever change in bowel habit blood/mucus suspected drug reaction alternating constipation/diarrhoea in elderly (fecal impaction)
What types are self limiting?
acute infective
and
teaveller’s
What should be given in moderate/severe Traveller’s?
antibiotics
4 examples of antimotility agents
codeine phosphate
loperamide
diphenoxylate
kaolin/opiate preparations
Can antimotility agents be given to children?
no
risk of respiratory depression or paralytic ileus
when to avoid antimotility agents
in severe gastroentritis
What is useful with antimotility agents in Traveller’s diarrhoea?
antibiotics
What is combined with antimotility agents for severe diarrhoea/dysentry?
antimicrobial therapy
2 opioid receptor agonsits used for diarrhoea
loperamide
diphenoxylate
Where does loperamide work?
mu opioid receptors in the myenteric plexus of the large intestine
How does loperamide work?
reduces peristalsis
increases transit time
enhances water/electrolyte reabsorption
reduces gut secretions
How long does loperamide take to work?
1 hour
loperamide dose
4mg initially
followed by 2mg as needed
side effects of loperamide
free from CNS side effects
CNS depression in overdose
What is diphenoxylate used in combination with?
atropine
age for diphenoxylate
over 13 years
What is diphenoxylate metabolised to?
difenoxin
action of dyphehnydramine
slows down contractions in the intestine
Side effects of dyphenhydramine
euphoria - abuse
dependence in prolonged use
Why is atropine given with diphenhydramine?
reduces abuse
combination produce with dihpenhydramine and atropine
Lomotil
Lomotil dose
4 times a day 4 tabs (2.5mg) followed by 2 tabs every 6 hours
Why is operamaide the drug of choice?
don’t need to add atropine
doesn’t cross BBB
no abuse
4 examples of bulking agents
wheat bran
isphaghula husk
methylcellulose
sterculia
What do bulking agents do?
control fecal consistency (in IBS, colostomy, ileostomy)
Are bulking agents recommended for acute diarrhoea?
no
what meds are not absorbed as well with antidiarrhoeal drugs?
slowly absorbed drugs - antiepileptics, m/r formulations antidiabetics anti-coagulants anti-malarials oral contraceptives
what to eat/drink with diarrhoea
clear fluids
light, easily digested foods
what to avoid
high sugar drinks
milk
why avoid milk?
temporary lactose intolerance due to damage by infecting organisms to lining of intestine
makes diarrhoea worse
