Malabsorption

Chapter 48 Malabsorption




Questions


image What are the clinical features of malabsorption?

image What are the most common causes of malabsorption?

image Why does coeliac disease occur?

Digestion involves enzymatic breakdown of proteins, carbohydrates and fats, and transport of nutrients across the intestinal epithelium into capillaries and lymphatics. Malabsorption implies a failure of these functions despite adequate nutritional intake. The most common causes in industrialized countries are pancreatic insufficiency, coeliac disease and Crohn disease (Fig. 3.48.1).


image

Fig. 3.48.1 The common bile duct, pancreas and duodenum showing the main causes of malabsorption.




Clinical features of malabsorption


Steatorrhoea is the passage of stools containing undigested fat. They are pale and bulky with an offensive smell, float on water and are difficult to flush away. Steatorrhoea is found when there is:


image failure of fat breakdown within the gut lumen (e.g. pancreatic enzyme deficiency in pancreatic disease) or failure of solubilization of fat through lack of bile salts in biliary insufficiency

image inadequate fat absorption, caused by decreased absorptive surface area, microorganisms or lymphatic obstruction.

Osmotic diarrhoea results if there are undigested nutrients that cause large amounts of water to be retained in the stools by oncotic pressure. It can be found in any form of malabsorption but particularly in disaccharidase deficiency. Osmotic diarrhoea is watery, unless undigested fats turn it into steatorrhoea.


Weight loss is common and may be the presenting feature of a malabsorption syndrome. In infants and children, failure to thrive is a common finding.


Deficiency of fat-soluble vitamins can occur where there is a significant failure of fat absorption. Vitamin D deficiency can lead to hypocalcaemia, osteomalacia and rickets, while lack of vitamin K can result in hypoprothrombinaemia and a bleeding tendency. Lack of vitamin A is a theoretical possibility but in practice it is rarely observed in malabsorption syndromes.


Potassium depletion causes thirst, polyuria, paraesthesiae and muscle weakness, while protein deficiency can cause muscle wasting, hypoproteinaemia and oedema. Anaemia is a common feature of malabsorption and may be caused by failure to absorb iron, folate and/or vitamin B12.


There may also be a variety of non-specific symptoms such as anorexia, abdominal distension, colicky pains, audible intestinal sounds (borborygmi) and excess flatus.

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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Malabsorption

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