W3 Malabsorption Flashcards
What is malabsorption?
Defective mucosal absorption caused by defective luminal absorption, mucosal disease, structural disorder
What are common causes of malabsorption?
- Celiac disease
- Crohn’s disease
- Post-infective
- biliary obstruction
- cirrhosis
What are uncommon causes of malabsorption?
- pancreatic cancer
- short bowel (incl. resection)
- drugs
- bacterial overgrowth
- parasites
What digestive diseases could cause protein malabsorption? (4)
- gastrectomy (poor mixing)
- exocrine pancreatic insufficiency
- trypsinogen deficiency
- congenital deficiency of intestinal enterokinase
What is enterokinase?
Enterokinase is an enzyme secreted from duodenal mucosa that changes inactive pancreatic secretion trypsinogen into active trypsin.
What absorptive disease could cause protein malabsorption? (9)
- Celiac disease
- tropical sprue (causes ulceration)
- short bowel syndrome
- jejunoileal bypass
- Methionine malabsorption syndrome (malt wee)
- Blue diaper syndrome (tryptophan malabsorption) (blue wee)
- defect in amino acid transporters e.g. Hartnup disease
- cystinuria
- oculocerebral syndrome of Lowe (lysine/arginine)
What is cystinuria?
Genetic disorder in which cystine builds up in kidneys and bladder and crystals can form.
What is Hartnup disease?
Genetic metabolic disorder associated with defect in amino acid transporters
What is oculocerebral syndrome of Lowe?
Genetic metabolic disorder in which kidney is affected leading to increased excretion of amino acids due to Fanconi syndrome (proximal tubule dysfunction)
List 3 causes of digestive fat malabsorption due to poor mixing.
- gastric resection
- autonomic neuropathy
- amyloidosis
What is amyloidosis?
Disease in which there are changes in proteins that causes them to be deposited in tissues and organs due to DNA mutation
What can cause fat malabsorption in the digestive phase associated with the liver and list 4 examples.
- decreased micelle formation/decreased bile acid synthesis/secretion due to:
- cirrhosis
- CCK deficiency
- small intestinal bacterial overgrowth
- biliary obstruction
What can cause fat malabsorption in the digestive phase associated with the pancreas and list 6 examples.
decreased lipolysis due to:
- chronic pancreatitis
- cystic fibrosis
- pancreatic/ampullary tumours
- low luminal pH
- excessive calcium ingestion
- lipase/co-lipase deficiency
What function does the liver have in the digestive phase of fat?
Micellar solubilisation with bile acid
What fuction does pancreas have in the digestive phase of fat?
Lipolysis
What can cause fat malabsorption in the absorptive phase and list 4 examples.
- decreased chylomicron formation and or mucosal absorption due to:
- celiac disease
- abetalipoproteinemia (problem with transfer protein)
- hypobetalipoproteinemia (problem with transfer protein)
- chylomicron retention disease
What can cause fat malabsorption in the post-absorptive phase and list 5 examples.
- defective lymphatic transport due to:
- primary intestinal lymphangiectasia
- lymphoma
- Whipple DIsease
- Trauma
- Retroperitoneal Fibrosis
What is hypobetalipoproteinemia associated with?
Low levels of LDL cholesterol
What is Primary Intestinal Lymphangiectasia characterised by?
Dilated intestinal lymph vessels
What can cause carbohydrate malabsorption in the digestive phase and give an examples?
-severe pancreatic insufficiency e.g. alpha-amylase deficiency
What can cause carbohydrate malabsorption in the absorptive phase and give 6 examples?
- Primary/acquired lactase deficiency
- Post-infectious lactase deficiency
- Celiac disease
- Crohn disease
- Sucrase-isomaltase deficiency
- trehalase deficiency
List 5 causes of vitamin B12 malabsorption.
- atrophic gastritis
- deficiency of gastric intrinsic factor
- pancreatic insufficiency/Z-E syndrome
- helminth infection/ SI BO
- Ileal Crohn Disease/Resection
What causes folic acid deficiency and give 4 specific examples?
- caused by diseases affecting the proximal small bowel
- celiac disease
- whipple disease
- tropical sprue
- alcoholism
What are the 4 fat soluble vitamins?
ADEK
How does atrophic gastritis affect vitamin b12 deficiency?
- There is impaired peptin/acid secretion which are essential for the liberation of vitamin b12 from the proteins in food.
- can also lead to deficiency of gastric intrinsic factor
What can cause deficiency of gastric intrinsic factor?
- pernicious anaemia
- antrectomy
How does pancreatic insufficiency/Zollinger-Ellison syndrome cause vitamin b12 malabsorption?
Both can lead to increased acidity and there is reduced release of b12 from r-binding protein in acidic environment.
What is Zollinger-Ellison syndrome?
Tumours that form in pancreas or duodenum which produce large amounts of gastrin that leads to excessive acid production.
What usually causes magnesium malabsorption?
- Loss of mucosal surface area
- and/or luminal binding by malabsorbed fatty acids i.e. magnesium bound to unabsorbed fatty acids
What can cause iron malabsorption?
- reduced mucosal surface area
- GI bleeding
What can cause zinc malabsorption and what is it?
Acrodermatitis enteropathica - inherited genetic disorder in which there is a defect in the zinc transport protein
What can cause copper malabsorption and what is it?
Menkes disease (kinky hair disease) - inherited genetic disorder of cellular copper transport
What are 3 causes of selective calcium deficiency?
- renal disease
- hypoparathyroidism
- inborn defect in the vitamin D receptor or vitamin D formation
What types of diseases can cause calcium malabsorption and give 2 examples?
- diseases that reduce intestinal surface area
- diseases that cause formation of insoluble calcium soaps with long chain fatty acids
- Celiac Disease
- Bile acid deficiency
