237 - Malabsorption

Question 1

what are the gastric causes of malabsorption?

Answer 1

• 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

Question 2

what are the bile system causes of malabsorption?

Answer 2

• 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)

Question 3

what are the pancreatic causes of malabsorption?

Answer 3

• 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

Question 4

what is absorbed in the ileum?

Answer 4

• proximal - fat soluble vits (ADEK), water and soluble vits

* distal - bilesalts, intrinsic factor/vit B12 comlez

Question 5

what is absorbed in the jejenum?

Answer 5

ADEK, folate, proteins, Ca

Question 6

what does the caecum do to the SI?

Answer 6

*prevents bacterial contamination and regulates flow of chyme from it

Question 7

what is absorbed in the colon?

Answer 7

water, electrolytes (minimal), SCFA from microbial fermentation

Question 8

what are the two types of glucose transporters?

Answer 8

• SGLT - Sodium coupled glucose-galactose transporter

* GLUT - Glucose transporter

Question 9

what are starch, maltose, lactose and sucrose broken down to?

Answer 9

• starch and maltose > glucose
• lactose > glucose and galactose
• sucrose > glucose and fructose

Question 10

name a brush border enzyme deficiency?

Answer 10

• 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

Question 11

what are defective transport causes of malabsorption?

Answer 11

*abetalipoproteinaemia - deficiency of two beta-lipoproteins > inability to make chylomicrons > impaired lipd and fat soluble vit absorption > steatorrhoea, acanthocytosis (star shaped RBC)

Question 12

what does a reduction in the absorption of fat soluble vitamins cause?

Answer 12

A - compromised mucosa and night blindness
D - rickets/osteomalacia
E - oxidant stress (CVD), haemolysis, neuropathy
K - Coagulopathy - prolonged PT

Question 13

what is lymphangiectasia?

Answer 13

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

Question 14

where does cholecystokinin act/ is produced?

Answer 14

produced - duodenum, jejenum, ileum, colon

acts on - pancreas (inc secretion) and gall bladder (contraction)

Question 15

where does gastrin act/ is produced?

Answer 15

• produced in G cells of gastric antrum

* acts on parietal cells in gastric body (H+ secretion)

Question 16

where does gastrin RH act/ is produced?

Answer 16

• produced in vagal nerves

* acts on g cells in gastric antrum (gastrin release)

Question 17

where does glucagon act/ is produced?

Answer 17

• produced in islets of langerhan (pancreas)

* acts on liver (incr glucose production and gylcogen breakdown)

Question 18

where does guanylin act/ is produced?

Answer 18

• produced - ileum, colon

* acts - SI and LI (fluid absorption)

Question 19

where does somatostatin act/ is produced?

Answer 19

• 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)

Question 20

where does vasoactive intestinal peptide act/ is produced?

Answer 20

• produced - enteric nervous system

* acts - SI and pancreas (inc secretions) and relaxes SI smooth muscle

Question 21

what is coeliac disease?

Answer 21

autoimmune inflammatory reaction to gliadin (contained in gluten) producing vilous atrophy and malabsorption

Question 22

who is at risk of coeliacs?

Answer 22

• genetic factors alleles DQ2 and * for human leukocyte antigen on Thcells - FHx 10% chance if 1st degree relative
• other autoimmune diseases

Question 23

how does gliadin cause a reaction in coeliacs?

Answer 23

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

Question 24

what are the signs of coeliacs?

Answer 24

• 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

Question 25

investigations for coeliacs?

Answer 25

• serology Ig A decr and Ig G anti TTG
• barium swallow - dilated SI
• endoscopy and biopsy - villous atrophy, hyperblastic crypts, hypercellular lamina propria