Consequences of fluid Loss from the GI Tract Flashcards
what is meant by “Insensible water loss”
water loss by transepidermal diffusion, so it is water that evaporates through the skin and respiratory tract
what do water intake and output do?
balance each other out
excretion (loss) of water and salts is usually small, but when is it large?
diarrhoea
sweating
vomiting
haemorrhage
losing a lot of electrolytes which can cause problems
kidneys can do what?
alter excretion to match gain with loss
why would you decrease salt intake?
to prevent hypotension
intake of salt should be?
similar to the output
list ways in which water, electrolytes and sodium chloride are lost
Defecation, diarrhoea Vomiting Urination Ventilation Sweating Menstruation
list ways in which water, electrolytes and sodium chloride are gained
Drinking
Metabolic (what we eat)
define diarrhoea
characterized by both an increase in frequency and weight of the stool
↑ frequency, with ↑ volume and fluidity of faeces
Greater than 3 unformed stools per 24hrs
give 2 reasons why diarrhoea occurs
- Failure of water absorption (Enterocytes lose ability to reabsorb as Toxins can bind)
- ↑ secretion (HCO3-, enzymes, Na+, due to crypt cell hyperplasia)
OR both
Causes of decreased absorption
↑ number of osmotic particles (osmotic diarrhoea)
↑ rate of flow of intestinal contents (deranged motility diarrhoea)
Abnormal increase in secretions of GIT (secretory diarrhoea)
Osmotic diarrhoea
occurs when too much water is drawn into the bowels
if a person drinks a solution with excessive sugar or excessive salt (an osmotically rich solution), this can draw water from the body into the bowel and cause osmotic diarrhoea
what can the build up of bacteria cause
de-conjugation of bile salts, which can cause osmotic or secretory diarrhoea
Deranged motility diarrhoea
the motility of the small intestine increases, meaning there is reduced time for reabsorption
this means that the volume of the fecal content will increase
some agents may promote secretion as well as motility
Secretory diarrhoea
increased secretion of ions from the crypt cells
very common in cholera
what can cause osmotic diarrhoea?
Disaccharidase deficiency (can be due to carbohydrate intolerance)
e. g. lactose intolerance
- due to lack of the brush border enzyme lactase, lactose cannot be broken down into Glucose and Galactose
what can cause secretory diarrhoea?
ACh, substance P, 5-HT and neurotensin act via ↑[Ca2+] (intracellular calcium levels) to increase rate of intestinal secretion
Excessive laxative use, defects in digestion and absorption, infections (cholera)
cholera survives acidic conditions of gut
enterotoxin stimulates adenylate cyclase, which increases cAMP levels leading to Na+ loss, Cl- loss (from crypt cells) and therefore uncontrolled water loss
what are crypts?
grooves between the villi (small fingerlike projections that line the small intestine and promote nutrient absorption)
how do you combat losing water, electrolytes and glucose
oral rehydration therapy so you can replace it all
what can inflammatory bowels disease cause?
chronic exudative diarrhoea, where you are producing a lot of fluid
why might GI stasis promote diarrhoea?
stimulating bacterial overgrowth, which could deconjugate the conjugated bile acids
what is dysentery?
painful, bloody, low volume diarrhoea
extreme urge to go but very little comes out
what is giardia, and what does it cause
a parasitic cause of diarrhoea
causes steatorrhoea and abdominal pain, maldigestion & malabsorption of lipids, CHOs, vit A, vit B12, folic acid.
causes of bloody diarrhoea?
- Chronic disease
- Ulcerative colitis
- Neoplasm