237 - Malabsorption Flashcards
what are the gastric causes of malabsorption?
- atrophic gastritis - inflammation of glandular tissue caused by chronic H.pylori infection and inflammation or autoimmune against parietal cells (intrinsic factor and acid)
- gastrectomy - reduction in acid and intrinsic factor - leads to bacteria in SI (no acid) and reduced vit b12 absorption >macrocytic anaemia
what are the bile system causes of malabsorption?
- obstructed bile duct (bile salts turn lipids into micelles for absorp)
- liver failure - clotting factors (vit K for 2,7,9,10) - test prothrombin and albumin
- defective bile salt reuptake from terminal ileum (cant be reused and liver cant replace quickly)
what are the pancreatic causes of malabsorption?
- pancreatic failure, pancreatitis, Cystic fibrosis
- reduced enzyme secretion so chyme cannot be broken down
- also zollinger ellison syndrome causes excess gastrin production causing peptic ulcers, inflammation and sometimes malabsorption
what is absorbed in the ileum?
- proximal - fat soluble vits (ADEK), water and soluble vits
* distal - bilesalts, intrinsic factor/vit B12 comlez
what is absorbed in the jejenum?
ADEK, folate, proteins, Ca
what does the caecum do to the SI?
*prevents bacterial contamination and regulates flow of chyme from it
what is absorbed in the colon?
water, electrolytes (minimal), SCFA from microbial fermentation
what are the two types of glucose transporters?
- SGLT - Sodium coupled glucose-galactose transporter
* GLUT - Glucose transporter
what are starch, maltose, lactose and sucrose broken down to?
- starch and maltose > glucose
- lactose > glucose and galactose
- sucrose > glucose and fructose
name a brush border enzyme deficiency?
- lactose intolerance congential (rare - more common after 5yo) or arise post infection/inflammation
- brush border lactase breaks down lactose to glucose and galactase. if defective lactose passes down bowel causing diarrhoea (osmotic), flatus and bloating (gut bacteria ferment and make acidic)
- investigate with lactose breath test -incr H2 exhale
- treat with low lactose diet, Ca in yogurt and lactase in milk
what are defective transport causes of malabsorption?
*abetalipoproteinaemia - deficiency of two beta-lipoproteins > inability to make chylomicrons > impaired lipd and fat soluble vit absorption > steatorrhoea, acanthocytosis (star shaped RBC)
what does a reduction in the absorption of fat soluble vitamins cause?
A - compromised mucosa and night blindness
D - rickets/osteomalacia
E - oxidant stress (CVD), haemolysis, neuropathy
K - Coagulopathy - prolonged PT
what is lymphangiectasia?
dilation of superficial lymphatic vessels due to congenital malformation or obstruction due to crohns, TB, malinancy, infection
*cause malabsorption of fat and fat soluble vitamins and protein loss
where does cholecystokinin act/ is produced?
produced - duodenum, jejenum, ileum, colon
acts on - pancreas (inc secretion) and gall bladder (contraction)
where does gastrin act/ is produced?
- produced in G cells of gastric antrum
* acts on parietal cells in gastric body (H+ secretion)
where does gastrin RH act/ is produced?
- produced in vagal nerves
* acts on g cells in gastric antrum (gastrin release)
where does glucagon act/ is produced?
- produced in islets of langerhan (pancreas)
* acts on liver (incr glucose production and gylcogen breakdown)
where does guanylin act/ is produced?
- produced - ileum, colon
* acts - SI and LI (fluid absorption)
where does somatostatin act/ is produced?
- produced - D cells in stomach and duodenum and delta cells in pancreatic islets
- acts - stomach (decr gastrin), intestine (incr fluid absorb/decr secretion), pancrease (decr endo/exocrine secretion), liver (decr bile flow)
where does vasoactive intestinal peptide act/ is produced?
- produced - enteric nervous system
* acts - SI and pancreas (inc secretions) and relaxes SI smooth muscle
what is coeliac disease?
autoimmune inflammatory reaction to gliadin (contained in gluten) producing vilous atrophy and malabsorption
who is at risk of coeliacs?
- genetic factors alleles DQ2 and * for human leukocyte antigen on Thcells - FHx 10% chance if 1st degree relative
- other autoimmune diseases
how does gliadin cause a reaction in coeliacs?
modified by Tissue TransGlutaminase in enterocytes breaking it down and releasing highly immunogenic antigens. Th cell response and IgA and IgG produced against TTG and gliadin. Macrophages produce IFN-gamma causing villous atrophy esp in duodenum and SI
what are the signs of coeliacs?
- diarrhoea and abdo pain and steatorrhoea
- abdo distension and flatus
- mouth ulcers
- lactose intolerance with incr damage
- failure to thrive, weight loss, fatigue/malaise
- anaemia (Fe and folate)
- osteopaenia/porosis due to Ca and vit D malabsorption
- neuro symptoms
- abnormal liver function - vit K deficiency
- dermatitis herpetiformis
investigations for coeliacs?
- serology Ig A decr and Ig G anti TTG
- barium swallow - dilated SI
- endoscopy and biopsy - villous atrophy, hyperblastic crypts, hypercellular lamina propria
