Malabsorption Flashcards
What is the definition of malabsorption?
“Defective mucosal uptake and transport of adequately digested protein, fat, carbohydrates or nutrients”
What is intraluminal digestion?
Pancreatic enzyme secretion and emulsification by bile salts
What is terminal digestion?
Enzymatic hydrolysis in brush border of small intestine
What is transepithelial transport?
Nutrients, fluid and electrolytes transported across epithelium
What can disturbance in electrolyte absorption lead to?
Osmotic diarrhoea
What are proteins, starches and triglycerides digested to?
Proteins → peptides
Starches → α-dextrins and disaccharides
Triglycerides → fatty acids and monoglycerides
What are a-dextrins and disaccharides hydrolysed by?
α-dextrins and disaccharides are hydrolysed by brush border enzymes and absorbed into cells
What do amphipathic bile salts form?
tiny spheres called micelles
What do long chain fatty acids require for absorption?
bile salts
What happens when Fatty acids and monoglycerides reach the epithelial cells of the villi?
Fatty acids and monoglycerides reach the epithelial cells of the villi and diffuse into the cells, leaving micelles behind in chyme
Where are bile salts reabsorbed?
the terminal ileum (enterohepatic circulation)
How do you identify steatorrhoea?
Stools may float in the pan – difficult to flush
Oily appearance and be foul smelling.
Which vitamins are fat soluble?
Vitamins A, D, E and K are fat-soluble
If fat absorption is impaired, deficiencies in these vitamins may occur
How does vitamin D deficiency affect calcium absorption?
Calcium absorption is greatly reduced in vitamin D deficiency and sometimes in generalized malabsorption
What is osteoporosis?
reduced bone density, inc risk of fragility fractures
What are some causes of osteoporosis?
Anorexia, smoking, alcoholism, malabsorption, steroid therapy, vitamin D/ calcium deficiency
How is osteoporosis diagnosed?
WHO osteoporosis criteria, DEXA bone scan T-SCORE -2.5 or worse
What is Osteomalacia and what causes it?
Definition:
Normal amount of bone but its mineral content is low.
Causes:
Vitamin D deficiency - inadequate sunlight, malabsorption (coeliac, intestinal resection, cholestasis), renal disease.
What can vitamin A deficiency cause?
blindness (begins with inability to produce tears)
What can vitamin B1 (thiamine) deficiency cause?
Beriberi; Wernickes
What can vitamin B2 deficiency cause?
angular stomatis; cheilitis
What can vitamin B6 deficiency cause?
polyneuropathy
What can vitamin B12 deficiency cause?
anaemia, SCDC
What can vitamin C deficiency cause?
scurvy
What can vitamin D deficiency cause?
osteomalacia
What can vitamin E deficiency cause?
bleeding disorders
What can vitamin K deficiency cause?
bleeding disorders
What can lead to B12 deficiency?
Gastric mucosal atrophy (pernicious anaemia) and terminal ileal disease
What does B12 require for absorption?
intrinsic factor
What is folate necessary for?
efficient thymidilate synthesis and production of DNA.
3 things to consider in deficiencies
Is the patient -
not getting enough in
not absorbing enough
losing too much
3 mechanisms of iron deficiency
iron intake (dietary)
↓ iron absorption (principally in the duodenum)
↑ iron loss (sloughed mucosal cells, bleeding)
What is coeliac disease?
Inflammatory condition of the small intestinal mucosa induced by an autoimmune reaction to the ingestion of gluten
What can be seen in coeliac disease from a histology point of view?
Villous atrophy/ intraepithelial lymphocytosis
How common is coeliac disease?
1 in 100 in the UK
What is the clinical presentation of coeliac disease in infants?
impaired growth, diarrhoea, vomiting, abdominal distension
What is the clinical presentation of coeliac disease in older children?
anaemia, short stature, pubertal delay, rickets, recurrent abdominal pain or behavioural disturbance
What is the clinical presentation of coeliac disease in adults?
chronic/recurrent iron deficiency anaemia, diarrhoea, abdominal pain, bloating, isolated nutritional deficiencies, reduced fertility, osteoporosis, osteomalacia abnormal liver function tests
How is Coeliac disease diagnosed?
Clinical history
Serological tests – endomysial (EMA) and tissue transglutaminase (tTG) antibodies
Duodenal biopsy via upper GI endoscopy
How is coeliac disease treated/managed?
gluten-free diet
What can lead to B12 deficiency?
Gastric mucosal atrophy (pernicious anaemia) and terminal ileal disease
What does B12 require for absorption?
intrinsic factor
What is folate necessary for?
efficient thymidilate synthesis and production of DNA.
3 things to consider in deficiencies
Is the patient -
not getting enough in
not absorbing enough
losing too much
3 mechanisms of iron deficiency
iron intake (dietary)
↓ iron absorption (principally in the duodenum)
↑ iron loss (sloughed mucosal cells, bleeding)
What is coeliac disease?
Inflammatory condition of the small intestinal mucosa induced by an autoimmune reaction to the ingestion of gluten
What can be seen in coeliac disease from a histology point of view?
Villous atrophy/ intraepithelial lymphocytosis
How common is coeliac disease?
1 in 100 in the UK
What is the clinical presentation of coeliac disease in infants?
impaired growth, diarrhoea, vomiting, abdominal distension
What is the clinical presentation of coeliac disease in older children?
anaemia, short stature, pubertal delay, rickets, recurrent abdominal pain or behavioural disturbance
What is the clinical presentation of coeliac disease in adults?
chronic/recurrent iron deficiency anaemia, diarrhoea, abdominal pain, bloating, isolated nutritional deficiencies, reduced fertility, osteoporosis, osteomalacia abnormal liver function tests
How is Coeliac disease diagnosed?
Clinical history
Serological tests – endomysial (EMA) and tissue transglutaminase (tTG) antibodies
Duodenal biopsy via upper GI endoscopy
How is coeliac disease treated/managed?
gluten-free diet
replace nutritional deficiencies
monitor bone density
What are investigations for chronic pancreatitis?
Faecal elastase-1
Produced by pancreas and passed in stool largely unaltered
Plain abdominal X-ray
Ultrasound/ CT
MRCP vs ERCP
What are some clinical features of pancreatic disease?
epigastric pain, often radiating to the back, food or alcohol may exacerbate the pain, weight loss.
How is chronic pancreatitis managed?
Remove precipitant (eg. alcohol) Pain control Treat diabetes (often need insulin) Pancreatic enzyme supplements – Creon Lipase, protease, amylase Vitamin supplementation
Nerve plexus blocks
Endoscopic stenting of strictures, surgery
What is cholestasis?
Cholestasis is the impairment of bile formation / bile flow
What is Primary sclerosing cholangitis (PSC)?
Inflammatory/ fibrotic process affecting intra/extrahepatic bile ducts
Leads to bile duct strictures
Aetiology unknown, but ~80% associated with IBD
Presents as pruritis, fatigue, jaundice
Ultimately leads to cirrhosis and liver failure - only proven treatment is liver transplantation
What drug can cause malabsorption?
orlistat - inhibits gastric and pancreatic lipase
