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 volume of fluid is ingested by the gut per day?
2000ml
What is the net excretion of faeces per day?
0.1L
What is osmotic diarrhoea?
Loose stool that results from a disturbance in electrolyte absorption.
What is steatorrhoea?
The presence of excess fat in the faeces.
In what diseases would you see steatorrhoea?
Cholestatic liver disease, pancreatitis and coeliac disease
If fat absorption is impaired, what vitamin deficiencies may occur?
A, D, E and K
What are potential risk factors for osteoporosis?
Anorexia, smoking, alcoholism, steroid therapy, vit D/calcium deficiency.
What happens to bone during osteomalacia?
Patients have a normal amount of bone but the mineral content is low.
What is the difference between rickets and osteomalacia?
Rickets and osteomalacia have the same cause, but rickets occurs while bones are still growing. Osteomalacia occurs once the epiphyses have fused.
What are the causes of rickets/osteomalacia?
Vit D deficiency, inadequate sunlight, coeliac disease, bowel resection, renal disease.
Mildy decreased calcium and phosphate with an increased alkaline phosphatase and parathyroid hormone.
Where is Vit A absorbed and what happens when it is deficient?
Small bowel. Xerophthalmia.
Where is Vit B1 absorbed and what happens when it is deficient?
Small bowel. Beriberi, Wernicke’s
Where is Vit B2 absorbed and what happens when it is deficient?
Small bowel. Angular stomatis, cheilitis.
Where is Vit B6 absorbed and what happens when it is deficient?
Small bowel. Polyneuropathy.
Where is Vit B12 absorbed and what happens when it is deficient?
Terminal ileum. Pernicious anaemia and subacute degeneration of spinal cord.
Where are Vit B12/IF complexes formed?
In the stomach.
What conditions can lead to B12 deficiency.
Gastric mucosal atrophy and terminal ileal disease.
Why is B12 required in the diet?
Is necessary for the synthesis of DNA in immature RBCs. Deficiency leads to macrocytic anaemia.
What are the causes of iron deficiency?
Poor iron intake, reduced iro absorption (particularly in duodenum) and increased iron loss (bleeding, sloughed mucosal cells).
What is coeliac disease?
Inflammatory condition of the small intestinal mucosa induced by an autoimmune reaction to the ingestion of gluten.
How common is coeliac disease?
1 in 100 in UK
What pathologies are found in coeliac disease?
Villous atrophy and intraepithelial lymphocytosis.
Describe the clinical presentation of coeliac disease in infants.
Impaired growth, diarrhoea, vomiting, abdo distension.
Describe the clinical presentation of coeliac disease in children.
Anaemia, short stature, pubertal delay, rickets, recurrant abdo pain behavioral disturbance
Describe the clinical presentation of coeliac disease in adults.
Chronic/recurrent iron deficiency, diarrhoea, abdo pain, bloating, isolated nutritional deficiencies, reduced fertility, osteoporosis, osteomalacia, abnormal LFTs
What is the average age of coeliac diagnosis?
4th-6th decade.
How does intestinal inflammation cause malabsorption in coeliac disease?
Increased intestinal transit -> reduced macronutrient absorption, negative calorie/protein balance.
How does villous atrophy cause malabsorption in coeliac disease?
Reduced surface area for absorption
What specific nutrient deficiencies are found in coeliac disease?
Iron, folate, calcium, vitamins, ADEK and B12
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 managed?
Gluten free diet, repeat biopsy,supplement nutritional deficiencies, monitor bone mineral density
Describe the features of Crohn’s disease.
Chronic transmural granulomatus inflammatory disorder. May affect any part of the GI tract, often in discontinuity. Twice as common in smokers.
What are the clinical features of Crohns disease?
Diarrhoea, abdo pain, weigh loss, malaise, nausea, vomiting, perianal disease. Small bowel involvement can lead to malabsorption (iron, folate, vit D). Fistulae, strictures, abcesses, ulceration and perforations.
Describe the features of ulcerative colitis.
Relapsing and remitting. Involves only the colon and inflammation may be continuous. Starts at the rectum. Only superficial inflammation seen.
How would you investigate IBD?
Colonoscopy/sigmoidoscopy + biopsies. Rule out infections. Blood tests to correct vitamin/mineral deficiencies. Radiology.
How would you manage IBD?
Establish severity of disease. Aim for prolonged mucosal healing. Systemic steroids. 5-aminosalicylates. Immunomodulators (azathioprine/mercaptopurine). Biological therapy (infliximab/adalimumab). Nutritional support. Surgery - complications of Crohn’s disease.
How does infliximab work?
Binds free and transmembrane TNF-alpha - central inflammatory cytokine.
What are the consequences of bowel resection?
Ileal - B12 deficiency, bile acid malabsorption
Short-bowel syndrome - electrolyte and fluid depletion, (treatment: hypertonic fluids, somatostatin analogues, loperamide)
What are the clinical features of chronic pancreatitis?
Epigastric pain often radiating to the back, food or alcohol exacerbating the pain, weight loss.
What are the causes of chronic pancreatitis?
Alcohol (>70%), familial, congenital (pancreas divisum), autoimmune, genetic (eg CFTR)
What are the complications of chronic pancreatitis?
Exocrine/endocrine insufficiency (eg diabetes), pancreatic duct strictures, jaundice, infection, haemmorrhage, rupture, portal hypertension (ascities/varices), increased risk of cancer.
What investigations woulf you perform if you suspected chronic pancreatitis?
Faecal elastase-1 (produced by pancreas and passed into stool unaltered). Plain abdo X-ray. Ultrasound/CT. MRCP/ERCP.
How do you manage chronic pancreatitis?
Remove precipitant (alcohol), pain control, treat diabetes, pancreatic enzyme supplements (Creon), vitamin supplementation, nerve plexus blocks, endoscopic stenting of strictures, surgery.
What is cholestasis?
The impairment of bile formation/flow.
What is primary sclerosing cholangitis?
Inflammatory/fibrotic process affecting intra/extrahepatic bile ducts. Leads to bile duct strictures. Aetiology unknonwn but 80% associated with IBD. Presents with pruritis, fatigue and jaundice. Leads to liver failure. Tx required.
Which drug may cause malabsorption?
Orlistat: inhibits gastric and pancreatic lipase.
How may small bowel bacterial overgrowth cause malabsorption?
Bacteria can deconjugate bile salts as well as metabolise B12.
