Malabsorption

Question 1

Normal absorption requires?

Answer 1

Normal absorption nRequires integrated gut response: nMotility: physical disruption nIntraluminal digestion: lumen and brush border nAbsorption through enterocytes nTransport via blood or lymphatic system

Question 2

Carbohydrates split into?

Answer 2

nComplex carbohydrates (polysaccharides =starch) split by salivary and pancreatic amylase & maltase into disaccharides.

Question 3

Lactose and sucrose split into?

Answer 3

nSucrase splits sucrose to glucose and fructose nLactase splits lactose to glucose and galactose

Question 4

Disaccharides split where? And into what?

Answer 4

nDisaccharides split at brush border enterocyte into monosaccharides :

Question 5

Monosaccharide are absorbed by the?

Answer 5

Monosaccharides absorbed through enterocyte into portal vein

Question 6

Discuss fat absorption.

Answer 6

nTriglycerides (TG) are split by pancreatic lipase to fatty acids (FA) and glycerol. nLong chain (FA) are solubilized by bile salts to form water soluble structure = micelles, which pass via enterocyte to lymphatics. Bile salts are reabsorbed in the terminal ileum (enterohepatic circulation). nTG containing medium chain (FA) can be absorbed without bile salts via enterocyte into portal vein

Question 7

Discuss absorption through the gi Tract

Answer 7

Question 8

Splitting and absorption of proteins?

Answer 8

nSplit by pancreatic enzymes such as trypsin or chymotrypsin, which are activated in the gut lumen, into oligopeptides, dipeptides and amino acids nAmino acids (AA) are absorbed through enterocyte into portal vein as single AA or dipeptides

Question 9

Vitamin absorption?

Answer 9

nB12 – intrinsic factor from parietal cells in stomach helps absorption in terminal ilium nWater soluble = B, C – follow flux of water from gut lumen through mucosa nFat soluble = A, D, E, K – follow pathway for fat

Question 10

Symptoms of b12 deficiency?

Answer 10

nDiarrhoea and pain on eating dairy products : lactose nPeripheral neuropathy: B12

Question 11

Conditions throughout the gi tract?

Answer 11

Question 12

Symptoms of malabsorption?

Answer 12

General symptoms:
Diarrhoea
Steatorrhoea
Weight loss
Specific to underlying cause or problem
Nutritional deficiencies : eg iron (breathless), Vit B12 (neurological) calcium (tetany), Vit K (bruising)
Crohn’s disease or pancreatic disease = abdominal pain
Past history eg radiation, surgery, travel

Question 13

Examination for malabsorption?

Answer 13

General findings:
Anaemia
Oedema
Weight loss
Specific to underlying problem
Nutritional deficiencies : eg iron (stomatitis), Vit B12 (neurological), calcium, Vit D (osteomalacia) K (bruising), albumin (oedema)
eg Crohn’s disease (perianal features), abdominal mass
Liver disease: jaundice

Question 14

Investigation for malabsorption?

Answer 14

Screening tests:
Full blood count, MCV, folate, Vit B12, ferritin, clotting time
Albumin, calcium
Tissue transglutaminase antibody (TTG-ab)
ESR, CRP, Immunoglobulins
Feacel elastase

Further investigations:
Endoscopy with biopsy
Barium follow through
U/S, ERCP, Abdominal CT
Endoscapsule
Specific tests:
Faecal fat collection
Lactose breath test for lactase deficiency
Glucose breath tests for bacterial overgrowth
Schilling test for B12 or whole body B12 absorption studies
Bile salt malabsorption test (SeCHAT)
Small bowel permeability studies
Pancreatic exocrine function tests

Question 15

Is the pancrease a peritoneal or retroperitoneal organ?

Answer 15

Retroperitoneal organ –exocrine (98%) and endocrine

Question 16

Pancrease stores and release what?

Answer 16

Exocrine : pancreatic acinar cells produce and store for release :
Lipase, amylase, colipase, phospholipase, proteases (trypsinogen and chymotrypsinogen)

Regulatory factors: cephalic, gastric (vagal) and intestinal phases ie neuronal and hormonal control
Stimulatory
Secretin: released when acid in duodenum – stimulates bicarbonate rich pancreatic secretion
Cholecystokinin: released in response to intraluminal food particularly fat - may cause release of enzymes

Question 17

Investigatations for excess pancreatic production?

Answer 17

Overt fat malabsorption (steatorrhoea) doesn’t occur until 85-90% of function lost. Large reserve means tests based on enzymes or breakdown products are insensitive

Serum biochemistry – serum lipase, amylase, trypsin (not useful due to large reserve)
Faecal tests
Fat estimation = increases (not popular with biochemists) collect over 3 days after 100g /day fat in diet. Normal excretion <6g/day (17 mmol)
Chymotrypsin = decreases (only useful in severe disease)

Elastase = decreases (not degraded in the SB – decreased levels in mod to severe failure)

Oral pancreatic function tests:
Fluorescein dilaurate test: (Pancreolauryl test)
Relies on pancreatic enzymes to release a soluble compound (marker) which can be absorbed and measured in the urine.
2 collections – test and control capsule (latter to correct for small bowel problems)
Prone to error if there are small bowel problems or poor urine collection
Less sensitive and specific if only moderate failure.

Oral pancreatic function tests:
Fluorescein dilaurate test: (Pancreolauryl test)
First 24 hour collection (test capsule):
Oral fluorescein dilaurate given (insoluble and not absorbed unless esterase present)
Digested by pancreatic esterase
Releases fluorescein (soluble) which is absorbed and excreted in the urine and measured
Second 24 hour collection (control capsule) to correct for small bowel causes of malabsorption
Fluorescein alone given (readily absorbed)
Quantity from test capsule as % of control = T/K ratio
Significant if <20%

Breath tests:
Measure the amount of 14CO2 in expired air after:
Labelled fatty acid (oleic acid)
Labelled triglyceride (triolein)
Impaired triglyceride absorption with normal fatty acid absorption indicates pancreatic disease

Duodenal sampling after intubation
All rely on passing an NG tube
Rely on analysis of duodenal aspirate following pancreatic stimulation by some means
Original (Lundh) – specified meal given
Now use intravenous – secretin or cholecystokinin to stimulate the pancreas.
Aspirate is assessed for bicarbonate (secretin) or enzyme activity
Only helpful in moderate to severe failure

Invasive and time consuming

Serum markers – no good
Stool –
faecal fat (not popular + not specific)
Faecal elastase +chymotrypsin (mod/severe disease)*

Urine collections – Pancreolauryl* reasonable
Breath tests – specialised centres
Direct intubation – specialised centres

Those used in clinical practice*.

In addition, simply use response to pancreatic enzyme supplements

Question 18

Imaging excess pancreatic function?

Answer 18

Plain abdominal x-ray – calcification (chronic pancreatitis – particularly alcohol)
Ultrasound – calcification, tumours, cysts
Spiral CT – as with ultrasound but more detailed
Endoscopic Retrograde Cholangio Pancreatography ERCP – duct system (allows intervention)
Magnetic Resonance Cholangio Pancreatography MRCP – non invasive and gives detail of pancreatic and bile duct system as well as of pancreas and liver
Endoscopic ultrasound – Defines small lesions in pancreas and allows biopsy – also good for small stones in bile duct

Question 19

Treatment for excess pancreatic excression?

Answer 19

Correct underlying abnormality:
Coeliac : avoid gluten
Pancreatic disease : replace enzymes
Crohn’s disease : treat inflammation
Ensure adequate nutrition and replacement
Dietician review
Vitamin replacement
Trace elements.

Question 20

Diseases that cause malabsorption?

Answer 20

Question 21

Pathology of chronic pancreatis?

Answer 21

Gland becomes fibrotic and exocrine and endocrine function fails:
Alcohol the most common cause in UK
Tropical (nutritional)
Hereditary
Trypsinogen and inhibitory protein defect
Cystic fibrosis
Pathogenesis: possibly due to inappropriate activation of enzymes within the pancreas eg unopposed trypsin activity

Question 22

Signs of chronic pancreatitis?

Answer 22

Early disease = asymptomatic (may or may not have past history of recurrent bouts of acute abdo pain and pancreatitis)

Acute on chronic pancreatitis may still occur with its complications of pseudocysts etc

Later on in the course pain is severe and persistent with associated weight loss – may mimic cancer of pancreas

Investigations:
Serum amylase – unhelpful
Faecal – elastase and chymotrypsin (low)
Pancreolauryl test (<20%)
Abdo xray – calcification
US – small gland and calcification
CT – atrophy, calcification and duct dilation
ERCP – as for CT
Trial of pancreatic enzyme supplements eg creon
Glucose tolerance test for diabetes

Exocrine failure leads to
Steatorrhoea (pale, offensive bulky stool which floats and is difficult to flush away)
very occasionally evidence of Vit ADEK malabsorption
weight loss due protease deficiency
Very occasionally jaundice due to narrowing of common bile duct through distorted pancreas

Endocrine failure – diabetes – polyuria, polydypsia, and weight loss

Question 23

Chronic pancreatitis treatment?

Answer 23

Pain control – analgesia (opiates, NSAIDS, tricyclic antidepressants, coeliac axis nerve blocks and surgery) – 60% become pain free with time (6-10 years)

Exocrine failure and malnutrition:
low fat, high calorie diet with vitamin supps
pancreatic enzymes supplements at meal times with acid suppression therapy
Medium chain triglycerides to decrease steatorrhoea

Endocrine - insulin

Question 24

Complications of chronic pancreatitis?

Answer 24

Pseudocysts – drain surgically or endoscopically
Cancer

Question 25

Coeliac disease pathology?

Answer 25

Gluten sensitive enteropathy
Subtotal villous atrophy, crypt hyperplasia and intraepithelial lymphocytosis
Prevalence in UK 1/100-1/300
Associated with other autoimmune disease eg thyroid, diabetes
Presentation varies – can be asymptomatic, or IBS like, or Fe deficiency etc
Diagnosed on TTG-ab
Gold standard : duodenal Bx on normal diet
Treatment : gluten free diet (wheat, rye and barley)

Question 26

IBD pathology?

Answer 26

Any site in the luminal gut – classically TI (occasional B12 deficiency)
Malabsorption usually only a problem if there is extensive small bowel involvement or after extensive surgery
Treatment: steroids, immunuosuppressive agents eg azathioprine, and biologics eg anti TNF

Question 27

Causes of chronic pancreatitis?

Answer 27

Tropical Sprue
Acute or chronic infection in developing world
Severe diarrhoea and folate deficiency occur
Antibiotics and folate supplements

Whipple’s disease
Uncommon, middle aged- men
Tropheryma Whipplei
Multisystem disease eg pleurisy, CNS, arthritis, gut
Treatm with antibiotics

Radiation enteritis
Usually presents a number of years later
Bowel may be strictured
Secondary bacterial overgrowth

Bacterial overgrowth
Seen in any situation where the small bowel is anatomically abnormal eg Crohn’s, previous surgery, radiation damage, scleroderma, diverticulosis
Treat with antibiotics eg tetracycline orally

Surgical resection (short gut syndrome)
Usually have 3-5m of small bowel
Problems arise if more than a half removed
Severe if <1m left (particulary if lost colon)
May need Total Parenteral Nutrition (TPN)

Common causes of short gut –
Crohn’s resections
Acute vascular events e.g. ischaemia resulting in infarction