Impaired absorption of nutrients from the small intestine
- Sometimes runs in families
- Age, gender, and lifestyle as risk factors depend on the cause
Malabsorption occurs when the small intestine cannot absorb nutrients from food passing through it. The disorder may cause various symptoms, including diarrhoea and weight loss. If malabsorption is left untreated, certain nutritional deficiencies can develop, which may lead to further problems, such as anaemia or nerve damage (see Nutritional neuropathies).
What are the causes?
Malabsorption is due to disorders that result in inadequate breakdown of food during digestion, damage to the lining of the small intestine, or impairment of motility, which is the ability of the muscular intestinal walls to contract.
In some cases, the small intestine cannot break down food because digestive enzymes or juices are missing or in short supply. For example, disorders affecting the pancreas, the organ that produces digestive juices, may prevent the breakdown of food. Such disorders include chronic pancreatitis and cystic fibrosis. Sometimes, there is a problem in breaking down a specific nutrient. For example, people with lactose intolerance lack an enzyme in the intestine needed to break down the sugar lactose from milk.
Damage to the lining of the intestine may result from inflammation due to disorders such as coeliac disease and Crohn’s disease and certain infections, such as giardiasis. As a result, nutrients are unable to cross the lining and pass into the bloodstream. In the autoimmune disorder scleroderma, changes in the structure of the intestinal walls affect motility and lead to malabsorption of nutrients. Diabetes mellitus may cause abnormal motility and malabsorption by damaging the nerves that supply the muscles in the intestinal walls.
What are the symptoms?
The most common symptoms of mal-absorption include:
Bulky, pale, foul-smelling diarrhoea.
Flatulence and abdominal bloating.
Abdominal pain with cramps.
Tiredness and weakness.
Left untreated, malabsorption can lead to deficiencies in vitamin B12 and iron, which may result in anaemia, the symptoms of which include pale skin and shortness of breath. A deficiency of vitamin B12 can also affect the spinal cord and peripheral nerves, causing numbness and tingling in the hands and feet.
How is it diagnosed?
Your doctor may arrange for a variety of blood tests to look for anaemia, vitamin deficiencies, and other signs of malabsorption. If the doctor suspects that your pancreas is damaged, he or she will probably arrange additional tests to assess its function. A test may be carried out to confirm the enzyme deficiency that causes lactose intolerance.
Further tests may be carried out to check for other disorders of the small intestine. You may have a blood test to look for the antibodies that are present in coeliac disease. A special X-ray in which barium is used to highlight the inside of the small intestine (see Contrast X-rays) may be carried out to look for damage to the digestive tract caused by Crohn’s disease. You may also require an endoscopy to obtain a sample of intestinal tissue for microscopic analysis.
What is the treatment?
If possible, the underlying cause of the malabsorption is treated. Coeliac disease can usually be treated with a special diet, and Crohn’s disease usually responds to corticosteroids or mesalazine (see Aminosalicylate drugs). If the cause of malabsorption is giardiasis, antiprotozoal drugs will be prescribed. Specific nutritional deficiencies can be corrected by taking vitamin and mineral supplements (see Vitamins, and Minerals).
If you are severely malnourished, you may need treatment in hospital, where you will be given intravenous nutrients or special liquid food supplements.
Most disorders that lead to malabsorption can be treated effectively, and the majority of affected people recover fully from the condition.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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