GIT - Constipation and Diarrhoea Flashcards
What is constipation? What are the symptoms associated? What are complications associated?
is a symptom not a disease
infrequent and/or unsatisfactory defacation fewer than three times per week
- passing hard stools
- straining
- incomplete or painful defacation
- bloating
complications
- haemorrhoids
- fissures
What are the risk factors contributing to constipation?
female gender - pregnancy
age - >65 yrs
low caloric intake
sedentary lifestyle
ignoring the urge to defecate
certain conditions/diseases
smoking
eating too little fibre
drinking too little water
change in routine - travel
frequent use of laxatives
medications - opioids, antacids with aluminium, antidepressants, iron supplements, diuretics
What are the types of treatment for constipation?
bulk forming
stimulant
osmotic
stool softeners
How do bulk forming laxatives work? What are examples? Who can use it?
dietary fibres, bran, ispaghula husk, methylcellulose and stericulia
absorbs water into the intestine, increasing faecal bulk and stimulating peristalsis
- is not absorbed from the intestine
- onset is up to 72 hrs
safe for long term use
safe for use by the elderly and patients with IBS, colostomies and diverticulosis
How do stimulant laxatives work? What are examples?
anthraquinones (Senna), diphenylmethanes (bisacodyl), 5-HT 4 agonist (prucalopride), fixed oil (castor oil)
increases water and electrolyte secretion by the mucosa
stimulates sensory nerve endings in GI mucosa causing increased peristalsis
- results in watery stool as faeces are moved through the bowel too rapidly to allow colonic absorption of faecal water
- 8-12 hr onset = usually given at night
What are the disadvantages of stimulant laxatives?
chronic, long-term use of stimulant laxatives can lead to loss of colon function
- constipation becomes worse and unresponsive to laxatives
- not recommended for chronic use as it can cause abdominal cramps
avoid in intestinal obstruction
damages the epithelium, causes melanosis coli and apoptosis
- melanosis coli may be harmless or linked to a possible increased risk of colon cancer
How do stool softening laxatives work? What are examples? Who can use it?
docusate, glycerol, liquid paraffin, arachis oil (peanut oil)
prevents hardening of the faeces by adding moisture to the stool
becomes emulsified with stool, decreasing surface tension of the faecal mass
- allows water to penetrate into the stool
used to prevent constipation
- can be used by patients who should avoid straining, patents recovering from childbirth/rectal, abdominal or pelvic surgery
What are the types of osmotic laxatives? How do they work?
hyperosmolar salts or saline products = magnesium citrate/hydroxide/oxide/sulphate, sodium bisphosphate
- are insoluble and remain in lumen pulling water into colon
= increasing water in the faeces, bulk and peristalsis
lactulose
- draws water into intestine and promotes water and electrolytes retention
glycerin
- acts like Lactulose, increasing water in the faeces
What condition is lactulose beneficial for?
hepatic encephalopathy (liver disease)
- causes a reduction in intestinal production of ammonia
= acidic pH destroys urease-producing bacteria involved in the production of ammonia
colonic metabolism of sugars causes a laxative effect via an increase in intraluminal gas formation and osmolality
= leads to a reduction in transit time and intraluminal pH (more acidic)
promotes increased uptake of ammonia by colonic bacteria
= utilize the trapped colonic ammonia as a nitrogen source for protein synthesis
What are other uses of laxatives?
bowel cleaning preparations
- used before colonic surgery, colonoscopy or radiological examination to ensure the bowel is free of solid contents
peripheral opioid receptor antagonists
- block/decrease the GI effects of opioids without affecting their central analgesic effects
= naloxegol, methylnaltrexone bromide
What is diarrhoea? What is its pathophysiology?
abnormal passing of loose or liquid stools with increased frequency, increased volume, or both
pathophysiology
- increased active anion secretion
- decreased absorption of water and electrolytes
What are the causes of diarrhoea?
non-infectious
- normal mucosa = osmotic diarrhoea, mal-absorption
- abnormal mucosa = IBD, coeliac disease, microscopic colitis, eosinophilic and allergic gastroenteritis, radiation enteritis
infectious
- bacterial, viral or parasitic
= mainly from the faecal-oral route
What are the treatment options for diarrhoea? How do they work?
oral rehydration therapy (ORT)
- main treatment to prevent or correct diarrhoea dehydration and to maintain the appropriate fluid intake once rehydration is achieved
= potassium chloride with sodium chloride, disodium hydrogen citrate with glucose, potassium chloride and sodium chloride
intravenous rehydration fluid
- for patients with sever dehydration and those unable to drink
anti-motility drugs
- Mu-Opioid receptor agonist, decreases the activity of the myenteric plexus
= loperamide
antibiotics
