237 - Malabsorption Flashcards
Diarrhoea can result after a change in absorption or secretion of just what %?
1% increase
Describe osmotic diarrhoea
Caused by ingestion of poorly absorbed osmotically active substance (non-electrolyte) that retains fluid in the lumen.
eg. ions - Mg, sulphate, phosphate
Sugars - mannitol, sorbitol
Lactose deficiency
Lactulose
What are signs of osmotic diarrhoea?
Moderatly increases stool volume
Stops when feeding stops
Osmolality normal or increased
Ion gap>100
How do you calculate ion gap?
Ion gap = Osmolality - (2x (Na + K))
Describe secretory diarrhoea
Disordered electrolyte transportation causes
- net secretion of anions (chloride + bicarb)
- net inhibition of Na absoption
- Water can’t be absorbed (as it follows Na)
-> diarrhoea
What can cause secretory diarrhoea?
Cholera (exogenous) NE tumour (endogenous) Absence of Ion transporter (congenital chlorideorrhoea) Loss of GI surface area Intestinal ischaemia Rapid gut transit
What are the signs of secretory diarrhoea?
V large stool volume
Continues with no food
Normal osmolality
Ion gap
Name 5 diseases that cause malabsorption
Coeliac Pernicious anaemia Intestinal lymphangiectasia Glucose-galactose malabsorption Lactase deficiency
What mediates coeliac disease?
Autoantigen transglutimase
What are the symptoms and signs of coeliac?
Chronic diarrhoea Poor weight gain Distended abdomen Reduced s/c fat Muscle wasting (see on buttocks)
What blood results may you find in coeliac?
Microcytic hypochromic anaemia (Fe deficiency)
Low serum ferritin
High ALT (a mild transaminitis is assoc with coeliac)
High Alk Phos (?low vit D - osteromalacia)
Low selective IgA (anti tTG) - associated with autoimmune diseases
- IgG anti-tTG more specific to coeliac
If you take a SI biopsy in coeliac what will you see?
Villous atrophy - flat mucosa
Crypt hyperplasia - elongated
Dense inflammatory infiltrates
What other conditions are associated with coeliac?
Diabetes type I
Autoimmune thyroiditis
Selective IgA deficiency
Syndromes - downs, williams, turners
Describe glucose-galactose malabsorption
Autosomal recessive disease, where the SGLT1 transported is inactive.
SGLT1 absorbs glucose and galactose (and so lactose can’t be either as it breaks down into them)
Get osmotic diarrhoea
What is a test for glucose-galactose malabsorption?
H2 breath test (sometimes called lactose breath test)
Feed glucose - increased H2 exhaled feed Fructose (dif transporter) - normal H2 exhaled
What causes primary lactase deficiency?
congenital deficiency - very rare, osmotic diarrhoea from birth
Late onset - around 5 years old, mostly in asians
What is a secondary lactase deficiency?
Acquired deficiency - uncommon
May get transient deficiency after an infection or mucosal damage
What symptoms may you get with pernicious anaemia?
Tiredness
Light headed
Pins + needles
Sore mouth
What signs may you see in pernicious anaemia?
Glossitis (B12 deficiency)
Vitiligo (autoimmune - assoc)
Goitre (autoimmune thyroid disease - assoc)
What tests can you do for pernicious anaemia?
FBC - see macrocystic normochromic anaemia
Reduced selective IgA (autoimmune)
If thyroid disease TSH raised?
anti-parietal cell antibodies
anti-intrinsic factor antibodies
What is the management of pernicious anaemia?
B12 injections
Thyroid hormone replacement
Surveillance endoscopies - as gastric carcinoma increased risk with atrophic gastritis
What is intestinal lymphangietasia?
Dilation of the intestinal lymphatics and loss of lymph fluid/drainage in the GI tract
Causes:
- hypotroteineamia
- Oedema
- Lymohocytopoenia
- Malabsorption - of fat, fat soluble vitamins (ADEK) and iron
What vitamins are fat soluble?
ADEK
How can you manage intestinal lymphangietasia?
Restrict dietary long chain triglycerides that block the lymph flow
Supplement medium chain - that can be absorbed via mucosa into blood
Supplement ADEK
