Malabsorption Syndromes

Question 1

What nutrients are absorbed in the duodenum? And what is used to aid the digestion of these nutrients?

Answer 1

Pancreatic juice - bicarbonate, enzymes
Bile
Ion absorption
- Cl-, SO4, iron, magnesium, calcium

Question 2

What nutrients are absorbed in the jejunum? And what is used to digest these nutrients?

Answer 2

Intestinal brush border enzymes

Carbohydrates and vitamins
Glucose, galactose, fructose
Vitamin C, thiamine, riboflavin, pyridoxine, folic acid

Question 3

What are intraluminal disorders?

Answer 3

Maldigestion of food

Question 4

What are intramural disorders?

Answer 4

Malabsorption of food

Question 5

What are Malassimilation disorders?

Answer 5

Lumping together of malabsorption and maldigestion

Some diseases can effect both digestion and absorption, e.g. Crohn’s

Question 6

Define digestion

Answer 6

Conversion of ingested food into a form which can be absorbed

Question 7

Define absorption

Answer 7

The transfer of the digested foodstuff across the enterocyte

Question 8

What are some examples of intraluminal disorders?

Answer 8

Mixing disorders
- Post-gastrectomy

Pancreatic insufficiency
- Pancreatitis –> pancreas releases digestive enzymes, can effect nutrient absorption
- Pancreatic carcinoma
- Cystic fibrosis

Bile salt insufficiency
- Liver disease –> shortage of bile secretions
- Non-recycling of bile salts –> as a consequence of ileal surgery
- Drugs that interfere bile salt function, effect ability to absorb fatty acids

Question 9

What type of nutrients begins to be digested in the mouth?

Answer 9

Carbohydrates

Question 10

What are some examples of intramural disorders?

Answer 10

Loss of surface area for absorption
- e.g loss of bowel due to surgery

Defects in mucosal absorptive surface
- Coeliac disease
- Dissacharidase deficiency
- Inflammatory disorders of the gut
- Lymphatic obstruction

Question 11

What is the efficiency of small bowel absorption?

Answer 11

Fat –> 90-95%
Carbohydrates –> 80-85% starch and 96-98% of disaccharides
Protein –> 95-99%

Iron 6-20% –> women absorb more than men due to the menstrual cycle and more B12 and folate to recover red blood cells

Question 12

What is absorbed in the distal portion of the gut?

Answer 12

Fat, proteins, cholesterol, Vitamin A and D
Bile salts and Vitamin B12

Question 13

What is absorbed in the colon?

Answer 13

Vitamin K is formed by bacterial fermentation (from fibre)
Water

Question 14

What can happen after bariatric surgery to a patient’s ability to absorb nutrients?

Answer 14

Slightly limited ability to absorb certain nutrients due to having a portion of their digestion system removed
- regular blood tests required
- more likely to be anaemic from lack of iron absorption, or have osteoporosis from lack of calcium absorption (lower ability), bone density may need to be checked (DEXA)
- may need supplements

Question 15

What are the main bacteria found in the stomach?

Answer 15

Lactobacilli

Question 16

What is the main cause of carbohydrate malabsorption?

Answer 16

Lack of amylase production

Question 17

What symptoms does carbohydrate malabsorption have?

Answer 17

• Osmotic diarrhoea
  Caused by the presence of osmotically active non-absorbed carbohydrates in the intestinal lumen. When glucose is absorbed, sodium is also absorbed (1 molecule each)
• Fluid retention
• Addition of other fluid
• Intestinal bloating
• Abdominal cramps and diarrhoea

Question 18

Why does carbohydrate malabsorption cause osmotic diarrhoea?

Answer 18

For every molecule of glucose, 1 molecule of sodium is also absorbed
Sodium-potassium pump maintain the homeostasis in the intestinal cell, K in and Na out, this helps with glucose absorption.

Low ability to absorb carbohydrates will cause an accumulation of sodium which will cause an accumulation of water which will then be excreted as osmotic diarrhoea.

Question 19

Describe lactose malabsorption

Answer 19

A type of carbohydrate malabsorption syndrome

Lactose needs to be broken down by lactase to a monosaccharide to be absorbed.
A deficit of lactase will reduce the amount the amount of lactose that can be absorbed.

Lactose will enter the small intestine and bacteria will ferment lactose to form short-chain fatty acids.
In the cases of lactose deficiency more SCFA can be produced than what the body can absorb leading to an osmotic balance. Water will be brought into the lumen and cause osmotic diarrhoea.
1 out of 3 people are lactose deficient in the UK, and do not form enough lactase. A small change in the gene expressing the protein.

Question 20

What gases are formed in the gut?

Answer 20

Carbon dioxide, nitrogen and hydrogen

Question 21

What are the consequences of carbohydrate malabsorption?

Answer 21

• Low levels of carbohydrate secretion
• Increase in secretion of cortisol, glucagon, T3 and T4, adrenaline
• Increased ketone production –> hormones breakdown FA from adipose tissue to form glucose and ketone bodies in the liver. Can be measured in urine
• Decrease glycogen stores –> difficult to measure, requires biopsy

The hormonal changes cause the breakdown of body fat and protein to replace carbohydrates as energy substrates.
Patients may present as physically weak, and prone to fatigue, with reduced body fat stores and lean body mass.
If happening to someone with T1 diabetes, it can be serious.

Question 22

How can carbohydrate malabsorption be measured?

Answer 22

Breath test - hydrogen present, and the unabsorbed disaccharide is present. Hydrogen then absorbed into the blood and exhaled in breath.

Question 23

What are some causes of fat malabsorption?

Answer 23

• Pancreatic disease/ disorders (inflamed pancreas can lead to bile production disruption, not enough bile into the duodenum) –> can be treated with pancreatic enzymes
• Liver disease/ disorders
• Lack of bile absorption in the ileum (Ileum disorder, e.g Crohn’s disease) –> 90% of bile to be reabsorbed in Ileum and travel back in circulation to liver to be stored in gall bladder, lack of store will decrease overall stores and impair ability to absorb fatty acids.
• Orlistat/ obesity treatments

Question 24

What can cause stertorrhea?
What is it?

Answer 24

Fat malabsorption
Fat-rich stools, often light colored and float. Fat droplets in toilet may be present

Question 25

What are some consequences of fat malabsorption?

Answer 25

• Steatorrhoea
• Deficiencies in fat soluble vitamins, A, D, K and E
• Undernutrition

Uncommon
- Formation of oxalate stones in the kidney

Question 26

Why can kidney stones be a result of fat malabsorption?

Answer 26

Dietary oxalic acid (a natural compound in some vegetables such as spinach) is normally complexed with calcium ions to form insoluble calcium oxalate which is passed out with faeces
In the presence of excess luminal fatty acids due to fat malabsorption most dietary calcium ions will bind to the fatty acid, this reduces the number of calcium ions for calcium oxalate
As a result, oxalic acid forms soluble sodium salts which are absorbed and filtered by the kidney and may precipitate out and form renal stones.

Can be seen in drugs used

Question 27

How can those on Orlistat reduce the risk of kidney stones?

Answer 27

Reduce oxalate in diet, less spinach, rhubarb, almonds

Question 28

What is the main cause of protein malabsorption?

Answer 28

Pancreatic disorders that effect the release/ production of enzymes

Question 29

What is the main clinical feature of protein malabsorption?

Answer 29

Oedma
- caused by the shortage of plasma proteins
- impairs the ability of the vascular system to retain fluid
- causing leakage into the interstitial spaces to form oedema

Protein is key for regulating fluid homeostasis, can cause homeostatic imbalance.
Fluid accumulates into interstitial spaces,

Question 30

What are some consequences of protein malabsorption?

Answer 30

• Loss of muscle can lead to weakness and difficulties in completing physical tasks. This can increase the risk of falls and fractures. Recovery from these injuries is much harder and longer.
• The immune system requires an adequate supply of protein to function. Protein deficiency due to malabsorption may predispose to infections.

Question 31

What are the main methods to diagnose malabsorption syndromes?

Answer 31

• Blood test
• Faecal fat test
• Image analyses (X-ray, colonoscopy/endoscopy, tomography)
• Collection of secretions (pancreas)
• Urine analysis (bentiromide test)
• Lactose absorption test
• Biopsy

Question 32

What are some general symptoms of malabsorption disorders?

Answer 32

• Diarrhoea
• Bloating
• Abdominal pain/ cramping
• Weight loss
• Flatulence