Malabsorption Syndrome Health Article

Definition

Malabsorption syndrome is an alteration in the ability of the intestine to absorb nutrients adequately into the bloodstream.

Causes and symptoms

Protein, fats, and carbohydrates (macronutrients) normally are absorbed in the small intestine; the small bowel also absorbs about 80% of the eight to ten liters of fluid ingested daily. There are many different conditions that affect fluid and nutrient absorption by the intestine. A fault in the digestive process may result from failure of the body to produce the enzymes needed to digest certain foods. Congenital structural defects or diseases of the pancreas, gall bladder, or liver may alter the digestive process. Inflammation, infection, injury, or surgical removal of portions of the intestine may also result in absorption problems; reduced length or surface area of intestine available for fluid and nutrient absorption can result in malabsorption. Radiation therapy may injure the mucosal lining of the intestine, resulting in diarrhea that may not become evident until several years later. The use of some antibiotics can also affect the bacteria that normally live in the intestine and affect intestinal function.

Risk factors for malabsorption syndrome include:

• family history of malabsorption or cystic fibrosis
• use of certain drugs, such as mineral oil or other laxatives
• travel to foreign countries
• intestinal surgery
• excess alcohol consumption

The most common symptoms of malabsorption include:

• anemia, with weakness and fatigue due to inadequate absorption of vitamin B₁₂, iron, and folic acid
• diarrhea, steatorrhea (excessive amount of fat in the stool), and abdominal distention with cramps, bloating, and gas due to impaired water and carbohydrate absorption, and irritation from unabsorbed fatty acids. The individual may also report explosive diarrhea with greasy, foul-smelling stools.
• edema (fluid retention in the body's tissues) due to decreased protein absorption
• malnutrition and weight loss due to decreased fat, carbohydrate, and protein absorption. Weight may be 80-90% of usual weight despite increased oral intake of nutrients.
• muscle cramping due to decreased vitamin D, calcium, and potassium levels
• muscle wasting and atrophy due to decreased protein absorption and metabolism
• perianal skin burning, itching, or soreness due to frequent loose stools

Irregular heart rhythms may also result from inadequate levels of potassium and other electrolytes. Blood clotting disorders may occur due to a vitamin K deficiency. Children with malabsorption syndrome often exhibit a failure to grow and thrive.

Several disorders can lead to malabsorption syndrome, including cystic fibrosis, chronic pancreatitis, lactose intolerance, and gluten enteropathy (non-tropical sprue.)

Tropical sprue is a malabsorptive disorder that is uncommon in the United States, but seen more often in people from the Caribbean, India, or southeast Asia. Although its cause is unknown, it is thought to be related to environmental factors, including infection, intestinal parasites, or possibly the consumption of certain food toxins. Symptoms often include a sore tongue, anemia, weight loss, along with diarrhea and passage of fatty stools.

Whipple's disease is a relatively rare malabsorptive disorder, affecting mostly middle-aged men. The cause is thought to be related to bacterial infection, resulting in nutritional deficiencies, chronic low-grade fever, diarrhea, joint pain, weight loss, and darkening of the skin's pigmentation. Other organs of the body may be affected, including the brain, heart, lungs, and eyes.

Short bowel syndromes—which may be present at birth (congenital) or the result of surgery—reduce the surface area of the bowel available to absorb nutrients and can also result in malabsorption syndrome.

Diagnosis

The diagnosis of malabsorption syndrome and identification of the underlying cause can require extensive diagnostic testing. The first phase involves a thorough medical history and physical examination by a physician, who will then determine the appropriate laboratory studies and x rays to assist in diagnosis. A 72-hour stool collection may be ordered for fecal fat measurement; increased fecal fat in the stool collected indicates malabsorption. A biopsy of the small intestine may be done to assist in differentiating between malabsorption syndrome and small bowel disease. Ultrasound, computed tomography scan (CT scan), magnetic resonance imaging (MRI), barium enema, or other x rays to identify abnormalities of the gastrointestinal tract and pancreas may also be ordered.

Laboratory studies of the blood may include:

• Serum cholesterol. May be low due to decreased fat absorption and digestion.
• Serum sodium, potassium, and chloride. May be low due to electrolyte losses with diarrhea.
• Serum calcium. May be low due to vitamin D and amino acid malabsorption.
• Serum protein and albumin. May be low due to protein losses.
• Serum vitamin A and carotene. May be low due to bile salt deficiency and impaired fat absorption.
• D-xylose test. Decreased excretion may indicate malabsorption.
• Schilling test. May indicate malabsorption of vitamin B₁₂.