Small Intestinal Disorders and Investigations Flashcards
What are the functions of the small intestine?
- Digestion
- Absorption
- Endocrine and neuronal control functions
- Barrier functions
Digestion
The breaking of food into its components
Absorption
The passage of nutrients into the body
Endocrine and neuronal control functions
Controlling the flow of material from the stomach to the colon
Barrier functions
- Regulating what stays in and gets out
- Maintaining a barrier against pathogens
How does the small intestine maintain a barrier against pathogens?
- Immune sampling
- Monitoring the presence of pathogens
- Translocation of bacteria
- Gut associated lymphoid tissue GALT
What is the average length of the small intestine by age 11?
250-450cm
How is a large surface area of the small intestine maintained?
- Villous architecture
- Constant turnover of cells in crypts and villi
Why is there a low bacterial population in the small intestine?
Toxic environment
- Digestive enzymes
- Bile salts
- Presence of IgA
How is control of digestion maintained?
- Decontamination of dirty food
- Requires a lot of fluid
- Controlled by hydrolysis to avoid fluid shifts
- Sophisticated control of motility
- Absorption against gradients
- Onward processing in the liver
What does the commencement of digestion in the stomach involve?
- Salivary amylase
- Pepsin
- Controlled breakdown to avoid osmotic shifts
Describe the basic digestion of proteins.
- Breakdown to ogliopeptides and amino acids
- Trypsin
- Final hydrolysis and absorption at brush border
Describe the basic digestion of fat.
- Pancreatic lipase
- Absorption of glycerol and free fatty acids via lacteal and lymphatic system
Describe the basic digestion of carbohydrates.
- Pancreatic amylase
- Breakdown to disaccharides
- Final digestion by brush border disaccharides
Symptoms of malabsorption
- Weight loss
- Increased appetite
- Bloating
- Fatigue
- Diarrhoea
- Steatorrhoea
Steatorrhoea
- Stool that is pale, foul smelling and high in fat content
- Due to fat malabsorption
- Stool less dense and floats
- May leave an oily mark
Signs of malabsorption
- Signs of weight loss
- Low or falling BMI
Signs of iron deficiency
- Anaemia
- Sore tongue
Signs of Ca, Mg and vitamin D deficiency
- Tetany
- Osteomalacia
Signs of vitamin A deficiency
Night blindness
Signs of vitamin K deficiency
Raised PTR
Signs of vitamin C deficiency
Scurvy
Signs of vitamin B complex deficiency
- Thiamine (memory, dementia)
- Niacin (dermatitis, unexplained heart failure)
What can clubbing be a non-specific sign of?
- Coeliac disease
- Crohn’s
What can scleroderma be a non-specific sign of?
-Systemic sclerosis
What can aphthous ulceration be a non-specific sign of?
- Coeliac disease
- Crohn’s
Dermatitis herpetiformis
Cutaneous manifestation of coeliac disease
How does dermatitis herpetiformis appear?
- Blistering
- Intensely itchy
- Scalp, shoulders, elbows, knees
- IgA deposit in skin
What investigations are there that test the structure of the GIT?
- Small bowel biopsy via endoscopy
- Small bowel study using barium
- White cell scan
- CT
- MRI enterography
- Capsule enterography
What tests can detect bacterial overgrowth?
- H2 breath test (lactulose or glucose substrate)
- Culture a duodenal or jejunal aspirate
Why is IgA sometimes less reliable than IgG as a test for coeliac disease?
A significant number of people don’t make IgA in the first place
Why should the total plasma IgA be checked?
Selective IgA deficiency is relatively common about 0.1-1% of the population but 2-3% of coeliacs
What tests can be used to diagnose coeliac disease?
- Distal duodenal biopsy (villous atrophy)
- HLA status
What is the prevalence of coeliac disease?
- 1:111 in UK
- 1:300 clinical diagnosis
What is coeliac disease a sensitivity to?
Gliadin fraction of Gluten
Where is gliadin found?
- Wheat
- Rye
- Barley
What is the pathology behind coeliac disease?
- Produces an inflammatory response thought to be via tissue transglutaminase
- Partial or subtotal villous atrophy
- Increased intra-epithelial lymphocytes
What is the gold standard diagnostic test for coeliac disease?
Distal duodenal biopsy
What serology is looked for in coeliac disease?
- Anti- endomysial IgA
- Anti Tissue transglutaminase
- Anti gliadin may help in children but not diagnostic in adults
What is the treatment for coeliac disease?
- Withdraw gluten
- Referral to state registered dietician
What conditions are associated with coeliac disease?
- Dermatitis herpetiformis
- IDDM
- Autoimmune thyroid disease
- Autoimmune hepatitis
- Primary biliary cirrhosis
- Autoimmune gastritis
- Sjogren syndrome
- IgA deficiency
- Downs syndrome
What complications can there be with coeliac disease?
- Refractory coeliac disease
- Small bowel lymphoma
- Oesophageal carcinoma
- Colon cancer
- Small bowel adenocarcinoma
What inflammatory causes of malabsorption are there?
- Coeliac disease
- Crohn’s
What infectious causes of malabsorption are there?
- Tropical sprue
- HIV
- Giardia lamblia
Tropical sprue
Folate deficiency which responds to antibiotics
Giardia lamblia
Unicellular parasite found in contaminated water that can cause hypogammglobulinaemia and responds to metronidazole
What can Whipples disease cause?
- Skin, brain, joints and cardiac effects
- Weight loss
- Malabsoprtion
- Abdominal pain
- PAS material in villi
Who is usually affected by Whipples disease?
Middle aged men
What organism is responsible for Whipples disease
Tropheryma whippelli
What infiltrative causes of malabsorption are there?
Amyloid
What impaired motility causes of malabsorption are there?
- Systemic sclerosis
- Diabetes
- Pseudo obstruction
What iatrogenic causes of malabsorption are there?
- Gastric surgery
- Short bowel syndrome
- Radiation
What pancreatic causes of malabsorption are there?
- Chronic pancreatitis
- Cystic fibrosis
Small bowel overgrowth can occur in any condition that affects…
- Motility
- Gut structure
- Immunity
How should bacterial overgrowth be treated?
Rotating antibiotics, each for 2 weeks
- Metronidazole
- Tetracylcine
- Amoxycillin
Vitamin and nutritional supplements
