Malabsorption

What is malabsorption?

Malabsorption is a condition caused by the decreased ability to digest and/or absorb nutrients from food. It is seen with a variety of diseases and can lead to general malnutrition or to symptoms associated with deficiencies in specific nutrients.

The body requires a steady supply of nutrients to build, repair, and maintain itself, to produce energy, enzymes, hormones, proteins, cells, tissues and bone, and to fight infections. Nutrients come from the diet and include many essential vitamins and minerals (micronutrients).

Food that is eaten is digested in three stages:

  • Proteins, fats, and complex sugars (carbohydrates) are broken down by stomach acids, enzymes produced by the pancreas, and bile from the liver. This process also releases micronutrients.
  • Nutrients are absorbed primarily by cells in the small intestines.
  • Nutrients are transported throughout the body and used or stored.

Any disruption or interference with this process can lead to malabsorption. The type and severity of deficiencies seen and the symptoms experienced depend on whether the problem affects general digestion and absorption or affects one or more specific nutrients.

Digestive problems

Fat, proteins and carbohydrates cannot be properly digested without bile and pancreatic enzymes. Insufficiencies in these substances can occur, for example, with liver and pancreatic diseases that limit their production, and with conditions such as cystic fibrosis that prevent pancreatic enzymes from reaching the digestive tract.

Absorption problems

If the intestines are unable to, or prevented from, absorbing nutrients, then the nutrients are eliminated from the body in the stool. This can happen when there is damage to the intestinal cells and tissues from disease or when the intestines have been shortened, such as due to surgery, reducing the surface area and the amount of time available in which nutrients can be absorbed from food as it passes through the digestive tract.

As an example of a specific deficiency, vitamin B12 absorption requires both stomach acid and intrinsic factor, a substance produced by parietal cells in the stomach. Stomach acid separates vitamin B12 from proteins and intrinsic factor binds with vitamin B12 enabling its intestinal absorption. A lack of either one prevents intestinal absorption and can lead to vitamin B12 deficiency. This can happen with advancing age, with medications that suppress stomach acid production, with gastric bypass surgeries, and with diseases that damage parietal cells or cause general malabsorption.

Transport problems

Once absorbed in the intestines, nutrients may be hindered from being transported throughout the body. This may be caused by problems with the lymphatic system such as lymphoma or the rare inherited disorder, abetalipoproteinemia.

Within these categories, there are a number of conditions and diseases that can cause malabsorption and the associated signs and symptoms. Below is a list of just some of these:

  • Cancers, including pancreatic cancer, lymphoma, stomach cancer
  • Coeliac disease—an autoimmune disease that causes damage to the lining of the intestines (intestinal villi)
  • Cystic fibrosis—a genetic condition that affects the pancreas and the transportation of pancreatic enzymes to the site of digestion
  • Damage to the intestines, such as from radiation treatment
  • Decreased intrinsic factor production
  • Diseases that affect circulation, such as congestive heart failure
  • Food intolerances and enzyme deficiencies
  • HIV and AIDS
  • Hyperthyroidism
  • Inflammatory bowel disease (Crohn’s disease and ulcerative colitis)
  • Liver diseases and structural abnormalities or blockages of bile ducts
  • Medications, such as phenytoin and those that inhibit stomach acid production
  • Pancreatic diseases and pancreatic insufficiency—can cause decreased amounts of pancreatic enzymes
  • Parasitic infections of the digestive tract, such as Giardia lamblia or a tapeworm
  • Scleroderma
  • Surgery, such as a bowel resection or gastric bypass
  • Zollinger-Ellison syndrome—a rare condition causing tumours in the pancreas and/or intestines
Signs and Symptoms

The signs and symptoms of malabsorption, and their speed of onset, depend upon the underlying cause as well as the type and severity of nutrient deficiencies. Some nutrients, such as vitamin B12, are stored by the body and symptoms only emerge when stores become depleted. Symptoms associated with insufficient pancreatic enzymes may not emerge until about 90% of the body's production capacity is disrupted.

Some of the most common signs and symptoms seen with general malabsorption include:

  • Persistent diarrhoea
  • Fatty stools that are loose and foul-smelling (steatorrhoea)
  • Failure to thrive (in children)
  • Abdominal pain, cramps, bloating, and gas

Other signs and symptoms may be due to general ill health or to specific deficiencies caused by malabsorption. They may include:

  • Weakness, fatigue
  • Fluid build-up in the abdomen (ascites)
  • Dry and scaly skin, rash
  • Inflammation of tongue (glossitis) and mouth (stomatitis)
  • Muscle wasting, unexplained weight loss
  • Nausea and vomiting
  • Swelling of the hands, feet and legs (peripheral oedema)
  • Easy bruising, bleeding gums
  • Numbness and tingling in feet and hands
  • Paleness
  • Muscle or bone pain

The following are some complications that can develop over time as a result of chronic malabsorption:

  • Anaemia
  • Delayed growth and development in children
  • Difficulty concentrating, confusion, and sometimes personality changes
  • Malnutrition
  • Osteoporosis
  • Deficiencies of micronutrients such as vitamin A, vitamin D, vitamin K and trace minerals
Testing

The purpose of testing may be to:

  • Screen those at risk for malabsorption because of an underlying condition such as cystic fibrosis
  • Detect malabsorption, identify its underlying cause(s), and evaluate the types and severity of nutrient deficiencies present
  • Detect complications such as anaemia
  • Monitor the effectiveness of treatment in people with malabsorption

There is no single test that can identify malabsorption or the underlying cause. Typically, a doctor will take into account many factors when requesting tests, including results from a physical examination, family history, medical history, and signs and symptoms. Testing will often be performed in steps with results leading toward a diagnosis while ruling out other possible causes. Testing typically involves requesting:

  • An initial set of general tests that evaluate body organs, cells, and digestion and that look for a cause for a person's persistent diarrhoea, one of the most common symptoms of malabsorption (NICE recommend full blood count, ESR or CRP and coeliac antibodies as a minimum in those with suspected inflammatory bowel syndrome for example).
  • Specific follow-up tests that are used to detect or exclude diseases associated with malabsorption and to identify specific deficiencies and/or complications

Laboratory Tests

Initial testing may include:

  • Full blood count (FBC) – to evaluate red blood cells to detect anaemia and white blood cells to detect infections
  • Renal and liver function tests – to evaluate proteins, electrolytes, and organ function, including the liver
  • Erythrocyte sedimentation rate (ESR) or C-Reactive protein (CRP) – to detect inflammation in the body which may be caused, for example, by inflammatory bowel disease
  • Stool culture – to detect bacterial infection or bacterial overgrowth as cause of persistent diarrhoea
  • Ova, cysts and parasite examination (OCP) – to detect parasites as cause of persistent diarrhoea
  • Thyroid stimulating hormone (TSH) – to detect or rule out thyroid disease

Based upon initial testing results, the person's symptoms, and the doctor's suspicions, further testing may include one or more of the following:

  • Faecal calprotectin - to distinguish irritable bowel syndrome (IBS) from other pathologies (e.g. ulcerative colitis or crohn's disease)
  • Vitamin B12, vitamin D, vitamin A – to detect deficiency
  • Prothrombin time (PT) – to detect vitamin K deficiency
  • Coeliac disease tests – to help diagnose this condition
  • Cystic fibrosis tests – to detect this disease
  • Faecal elastase – to evaluate pancreatic function
  • CA125 – ovarian cancer is a rare cause of new gastrointestinal symptoms and this marker is recommended by NICE for use in women with new symptoms if aged 40 years and above.
  • Faecal occult blood test – area of controversy but can be used to detect bleeding in the digestive tract 

Other laboratory tests sometimes requested include:

  • Methylmalonic Acid (MMA) – to detect early vitamin B12 deficiency
  • Hydrogen breath test – to detect lactose intolerance and bacterial overgrowth in the digestive system (carbohydrate malabsorption)
  • Lactose absorption test – though this test is primarily used to detect a deficiency in the enzyme lactase (lactose intolerance), it may sometimes be used to identify malabsorption
  • Gastric hormones – rarely required, indicated in the presence of diarrhoea
  • Biopsy of the intestine

Non-Laboratory Tests

Testing to examine the digestive tract, liver, and/or pancreas is sometimes necessary and may include imaging investigations such as:

  • Abdominal ultrasound scan
  • Barium enema
  • CT scan
  • Endoscopy
  • Endoscopic retrograde pancreatography (ERCP)
  • SeHCAT (nuclear medicine scan for bile acid malabsorption)
Treatment

A person affected by malabsorption can work with their doctor, a dietician, or other health care professionals to address and manage their condition. Treatment of malabsorption typically includes one or more of the following:

  • Addressing the underlying cause to minimise malabsorption symptoms and intestinal damage
  • Replacing missing nutrients; this may include the use of oral pancreatic enzyme supplements and the replacement of minerals and vitamins 
  • Dietary advice, supplements and alterations, such as a gluten-free diet or high calorie shakes
  • Working with the doctor to develop a treatment plan that is tailored to an individual person's clinical situation
  • Some people may require artificial nutrition support such as feeding via a tube into the gut (enteral nutrition) or feeding into a vein (parenteral nutrition)
  • Monitoring the person's health status over time; this often involves performing laboratory tests such as a FBC, renal/liver function tests at regular intervals.