Malabsorption Syndromes Flashcards
What nutrients are absorbed in the duodenum? And what is used to aid the digestion of these nutrients?
Pancreatic juice - bicarbonate, enzymes
Bile
Ion absorption
- Cl-, SO4, iron, magnesium, calcium
What nutrients are absorbed in the jejunum? And what is used to digest these nutrients?
Intestinal brush border enzymes
Carbohydrates and vitamins
Glucose, galactose, fructose
Vitamin C, thiamine, riboflavin, pyridoxine, folic acid
What are intraluminal disorders?
Maldigestion of food
What are intramural disorders?
Malabsorption of food
What are Malassimilation disorders?
Lumping together of malabsorption and maldigestion
Some diseases can effect both digestion and absorption, e.g. Crohn’s
Define digestion
Conversion of ingested food into a form which can be absorbed
Define absorption
The transfer of the digested foodstuff across the enterocyte
What are some examples of intraluminal disorders?
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
What type of nutrients begins to be digested in the mouth?
Carbohydrates
What are some examples of intramural disorders?
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
What is the efficiency of small bowel absorption?
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
What is absorbed in the distal portion of the gut?
Fat, proteins, cholesterol, Vitamin A and D
Bile salts and Vitamin B12
What is absorbed in the colon?
Vitamin K is formed by bacterial fermentation (from fibre)
Water
What can happen after bariatric surgery to a patient’s ability to absorb nutrients?
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
What are the main bacteria found in the stomach?
Lactobacilli
What is the main cause of carbohydrate malabsorption?
Lack of amylase production
What symptoms does carbohydrate malabsorption have?
- 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
Why does carbohydrate malabsorption cause osmotic diarrhoea?
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.
Describe lactose malabsorption
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.
What gases are formed in the gut?
Carbon dioxide, nitrogen and hydrogen
What are the consequences of carbohydrate malabsorption?
- 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.
How can carbohydrate malabsorption be measured?
Breath test - hydrogen present, and the unabsorbed disaccharide is present. Hydrogen then absorbed into the blood and exhaled in breath.
What are some causes of fat malabsorption?
- 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
What can cause stertorrhea?
What is it?
Fat malabsorption
Fat-rich stools, often light colored and float. Fat droplets in toilet may be present
What are some consequences of fat malabsorption?
- Steatorrhoea
- Deficiencies in fat soluble vitamins, A, D, K and E
- Undernutrition
Uncommon
- Formation of oxalate stones in the kidney
Why can kidney stones be a result of fat malabsorption?
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
How can those on Orlistat reduce the risk of kidney stones?
Reduce oxalate in diet, less spinach, rhubarb, almonds
What is the main cause of protein malabsorption?
Pancreatic disorders that effect the release/ production of enzymes
What is the main clinical feature of protein malabsorption?
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,
What are some consequences of protein malabsorption?
- 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.
What are the main methods to diagnose malabsorption syndromes?
- Blood test
- Faecal fat test
- Image analyses (X-ray, colonoscopy/endoscopy, tomography)
- Collection of secretions (pancreas)
- Urine analysis (bentiromide test)
- Lactose absorption test
- Biopsy
What are some general symptoms of malabsorption disorders?
- Diarrhoea
- Bloating
- Abdominal pain/ cramping
- Weight loss
- Flatulence
