Malabsorption syndrome

Malabsorption syndrome refers to the signs and symptoms caused by the impaired absorption of nutrients from the diet (proteins, fats, carbohydrates, vitamins, or minerals).

Malabsorption may be the result of a defect in the gastrointestinal tract that may lead to nutritional deficiency or malnutrition.

It is usually related to disorders of the small intestine, which is the responsible for absorption of nutrients.

Malabsorption syndrome is a group of disorders with a complex pathophysiology. Malabsorption is the result of multiple causes that may depend on:

• The place or the root of the problem
• If it is a global deficiency or a partial deficiency of a specific (isolated) type of nutrient (carbohydrates, fats, iron, proteins, etc.).

The processes underlying digestion and absorption are interdependent.

Digestion is the breakdown of food into smaller units thanks to gastric juices, pancreatic enzymes and bile salts.

Absorption is the movement of nutrients from the wall of small intestines into the bloodstream.

Three steps are required for nutrient absorption:

1. Intestinal lumen: Where hydrolysis of the food take place
2. Intestinal mucosa: Where the nutrients are absorbed
3. Transport: Once absorbed, the nutrients are transported into the bloodstream

There are different types of malabsorption depending on the specific (isolated) nutrient affected:

Fat malabsorption

• Altered secretion of bile salts and/or pancreatic enzymes
• Bile salt deficiency
• Structural abnormalities of the bowel wall that prevent absorption
• Lymphatic obstruction

Carbohydrate malabsorption (lactose intolerance is the most common)

• Congenital or acquired lactase deficiency

Vitamins and trace elements

• Vitamin B12 deficiency is the most common. It may be the result of intrinsic factor deficiency, pancreatic insufficiency, bacterial overgrowth and secondary to bowel resection

There are also many diseases or conditions that reduce the intestinal absorption. They can be classified into:

Due to exocrine pancreatic insufficiency

• Chronic pancreatitis
• Cystic fibrosis
• Pancreatic cancer
• Pancreatic resection

Bile salt deficiency

• Cholestatic hepatitis
• Bacterial overgrowth
• Biliary obstruction

Diseases of the mucosa and bowel wall

• Celiac disease
• Crohn's disease
• Tropical sprue
• Short bowel syndrome
• Radiation enteritis
• Whipple's disease
• IgA immunodeficiency
• Amyloidosis
• AIDS enteropathy
• Lactase deficiency
• Mastocytosis
• Eosinophilic enteritis
• Giardiasis

Vascular and lymphatic causes

• Intestinal lymphangitis
• Congestive heart failure
• Abdominal tuberculosis
• Chronic mesenteric insufficiency
• Intestinal lymphoma

Other causes

• Post gastric or intestinal surgery
• Intestinal lymphagiesctasia
• Atrophic gastritis

There may be digestive symptoms and extraintestinal manifestation in relation to the nutritional deficiency.

Digestive symptoms

• Acute, intermittent or chronic diarrhea
• Foul-smelling, pasty, bulky and pale stools
• Weight loss

Hematological

• Microcytic anemia (iron deficiency)
• Macrocytic anemia (vitamin B12 deficiency)
• Bleeding (vitamin K deficiency)

Musculoskeletal system

• Osteoporosis and bone fractures (calcium and vitamin D deficiency)
• Tetany and paresthesia (calcium, magnesium, and vitamin D deficiency)

Skin and mucous membranes

• Hematomas and petechiae (vitamin K and vitamin C deficiency)
• Edema (protein and albumin deficiency)
• Nail abnormalities (iron deficiency)

Endocrine system

• Menstrual disorders, sexual impotence, and infertility (protein deficit)

Nervous system

• Peripheral neuropathy (vitamin B12 and thiamine deficiency)
• Visual disturbances (vitamin A deficiency)

Symptoms of protein malabsorption

• Weight loss and loss of muscle
• Albumin deficiency
• Edema, ascites, and heart failure (advanced stages)

Symptoms of carbohydrate malabsorption

• Osmotic (watery) diarrh
• Flatulence
• “Explosive” diarrhea due to the conjunction of meteorism and watery diarrhea

Depending on the macromolecular deficiency (fats, carbohydrates, proteins), the following diagnostic tests should be performed:

Recommended diagnostic tests in case of fat malabsorption:

• Sudan III stain test: The test will be positive when the percentage of fecal fat excreted is greater than 15% compared to the ingested fat.
• Quantitative test (Van de Kramer): 72-hour collection of stools, in which the patient must intake a fat overload of 100 g per day. The test will be positive (steatorrhea), if the fecal excretion is more than 6 grams per day.
• Near-infrared reflectance analysis (NIRA)
• Triolein breath test

Diagnostic tests in case of carbohydrate malabsorption (used to rule out lactose intolerance):

• D-Xylose absorption test
• Hydrogen breath test

Diagnostic tests in case of protein malabsorption:

• The most widely used technique is the measure of human alpha 1 antitrypsin by radioimmunoassay.

Complementary imaging tests may help the diagnosis:

• Abdominal ultrasound, Computed Tomography (CT), Nuclear Magnetic Resonance, Endoscopic Retrograde Cholangiopancreatography, and MRI-cholangiopancreatography.
• Barium meal (upper gastrointestinal series)
• Endoscopy and colonoscopy with intestinal biopsy
• Capsule endoscopy

Depending on the response to treatment, malabsorption syndrome can be divided into 4 groups:

• Curable malabsorption: When the initial cause has a specific curative treatment (intestinal parasite infection, pharmacological causes, tropical sprue, Whipple's disease, etc.)
• Complete control of absorption: When the cause is not curable, but it is possible to control intestinal absorption (Celiac disease, carbohydrate intolerance, bacterial overgrowth, etc.)
• Control of the underlying cause: When it is not possible to cure the underlying cause, but it is possible to control it (inflammatory bowel disease, Crohn's disease, intestinal lymphoma, etc.)
• Supportive treatment: When it is not possible to cure the underlying cause or control it (intestinal infarction, short bowel syndrome, small bowel cancer, etc.)

The rest of the treatment will be based on enteral nutrition. This can be achieved through oral supplements depending on the nutritional deficit (iron, vitamin B12, proteins, etc.), dietary guidelines and recommendations (Celiac disease, lactose intolerance, etc.), and parenteral (intravenous) nutrition in severe acute malnutrition.