Introduction
Malabsorption syndrome refers to a number of disorders in which nutrients from food are not absorbed properly in the small intestine.
*Certain disorders, infections, and surgical procedures can cause malabsorption.
*Malabsorption causes diarrhea, weight loss, and bulky, extremely foul-smelling stools.
*The diagnosis is based on typical symptoms along with testing of stool samples for fat and sometimes examination of a tissue specimen removed from the lining of the small intestine.
*The treatment depends on the cause.
Normally, foods are digested and nutrients are absorbed into the bloodstream mainly in the small intestine. Malabsorption may occur if a disorder interferes with the digestion of food or interferes directly with the absorption of nutrients.
Digestion can be affected by disorders that prevent adequate mixing of food with digestive enzymes and acid from the stomach. Inadequate mixing may occur in a person who has had part of the stomach surgically removed. In some disorders, the body produces inadequate amounts or types of digestive enzymes, which are necessary for the breakdown of food. For example, a common cause of malabsorption is insufficient production of digestive enzymes by the pancreas, as occurs with some pancreatic diseases, or by the small intestine, as occurs in lactase deficiency. Decreased production of bile, too much acid in the stomach, or too many of the wrong kinds of bacteria growing in the small intestine may also interfere with digestion.
Absorption of nutrients into the bloodstream can be affected by disorders that injure the lining of the small intestine. The normal lining consists of small projections called villi and even smaller projections called microvilli, which create an enormous surface area for absorption. Surgical removal of a large section of the small intestine substantially reduces the surface area for absorption (short bowel syndrome). Infections (bacterial, viral, or parasitic), drugs such as neomycin Some Trade Names NEO-RX and alcohol, celiac sprue, and Crohn's disease all may injure the intestinal lining. Disorders that affect the remaining layers of the intestinal wall, such as blockage of the lymph vessels by lymphoma (cancer of the lymphatic system) or poor blood supply to the small intestine, also reduce absorption.
Symptoms
Symptoms of malabsorption are caused by the increased passage of unabsorbed nutrients through the digestive tract or by the nutritional deficiencies that result from inadequate absorption.
The inadequate absorption of fats in the digestive tract results in stool that is light-colored, soft, bulky, and unusually foul smelling (such stool is called steatorrhea). The stool may float or stick to the side of the toilet bowl and be difficult to flush away. The inadequate absorption of certain sugars can cause explosive diarrhea, abdominal bloating, and flatulence.
Malabsorption can cause deficiencies of all nutrients or selective deficiencies of proteins, fats, sugars, vitamins, or minerals. People with malabsorption usually lose weight. The symptoms vary depending on the specific deficiencies. For example, a protein deficiency can cause swelling (edema) anywhere throughout the body, dry skin, and hair loss.
Diagnosis
A doctor suspects malabsorption when a person has chronic diarrhea, nutritional deficiencies, and substantial weight loss despite a healthy diet. Malabsorption is less obvious and often more difficult to recognize in older people than in younger people.
Laboratory tests can help confirm the diagnosis. Tests that directly measure fat in stool samples collected over 2 or 3 days are the most reliable ones for diagnosing malabsorption of fat, which is present in almost all malabsorption disorders. A finding of more than 7 grams of fat in the stool daily is the hallmark of malabsorption. Several other tests for measuring fat in stool are available that do not require the messy 3-day collection of stool. Other laboratory tests can detect malabsorption of other specific substances, such as lactose or vitamin B12.
Stool samples are examined with the unaided eye as well as under the microscope. Undigested food fragments may mean that food passes through the intestine too rapidly. In a person with jaundice, stool with excess fat indicates decreased production or secretion of bile. Sometimes parasites or their eggs are seen under the microscope, suggesting that malabsorption is caused by a parasitic infection.
A biopsy may be needed to detect abnormalities in the lining of the small intestine. The tissue is removed through an endoscope (a flexible viewing tube equipped with a light source and a small clipper) passed through the mouth and into the small intestine.
Pancreatic function tests are performed if the doctor thinks that the cause of malabsorption may be the insufficient production of digestive enzymes by the pancreas. However, some of these tests are complex, time-consuming, and invasive. In one test, a tube is passed through the mouth and guided to the small intestine, so that intestinal fluids containing pancreatic secretions can be collected and measured. In another test, the person swallows a substance that requires pancreatic enzymes for its digestion. The products of digestion are then measured in the urine.
Bacterial Overgrowth Syndrome
Bacterial overgrowth syndrome is a disorder in which poor movement of intestinal contents allows certain normal intestinal bacteria to grow excessively, causing diarrhea and poor absorption of nutrients (malabsorption).
*Some conditions and disorders slow or stop the movement of contents through the intestines.
*Some people have no symptoms, whereas others have weight loss, nutritional deficiencies, and diarrhea.
*The diagnosis is based on symptoms that occur after people have had certain types of surgery.
*Antibiotics can eliminate the excess bacteria.
The normal steady movement of intestinal contents (peristalsis) is important to help maintain a proper balance of bacteria in the small intestine. Conditions in which intestinal contents slow or pool in one place allow excess bacteria to grow. Such conditions include certain types of surgery on the stomach, intestines, or both. Disorders such as diabetes, systemic sclerosis, and amyloidosis also can slow peristalsis, causing bacterial overgrowth.
The excess bacteria consume nutrients, including vitamin B12 and carbohydrates, leading to lower calorie intake and vitamin B12 deficiency. The bacteria also split bile salts, which are secreted by the liver to aid digestion. The loss of bile salts causes difficulty absorbing fats, leading to diarrhea and poor nutrition.
Some people have few symptoms or only weight loss. Others have severe nutritional deficiencies, diarrhea, or both.
Diagnosis and Treatment
Doctors base the diagnosis on typical symptoms that occur in people who have had certain types of surgery. Sometimes they take a fluid sample from the small intestine by means of a thin plastic tube passed through the nose. Some doctors instead perform breath tests, such as the 14C-xylose breath test. In this test, the person drinks a liquid containing a special, faintly radioactive marker (carbon-14) attached to a sugar (xylose). If the xylose is broken down by the excess bacteria, the carbon-14 can be detected in the person's breath.
Most people get better with antibiotics given by mouth for 10 to 14 days. Doctors prescribe supplements to correct any nutritional deficiencies.
Celiac Sprue
(Nontropical Sprue; Gluten Enteropathy; Celiac Disease)
Celiac sprue (nontropical sprue, gluten enteropathy, celiac disease) is a hereditary intolerance to gluten, a protein found in wheat, barley, and oats, which causes characteristic changes in the lining of the small intestine, resulting in malabsorption.
*The intestinal lining becomes inflamed after a person ingests the protein gluten.
*Symptoms in adults include diarrhea, malnutrition, and weight loss; symptoms in children include abdominal bloating and bulky, very foul-smelling stools.
*The diagnosis is based on typical symptoms and examination of a tissue specimen removed from the lining of the small intestine.
*Most people do well if they maintain a gluten-free diet.
Celiac sprue affects as many as 1 out of 150 people in southwestern Ireland, 1 out of 300 people in Europe, and perhaps 1 out of 250 people in the United States, yet it is extremely rare in Africa, Japan, and China. There is a genetic component. About 10% of people with celiac sprue have a close relative with the disease. In this disease, gluten, a protein found in wheat and, to a lesser extent, barley, rye, and oats, stimulates the immune system to produce certain antibodies. These antibodies damage the inner lining of the small intestine, resulting in flattening of the villi. The resulting smooth surface leads to malabsorption of nutrients. However, the small intestine's normal brushlike surface and function are restored when the person stops eating foods containing gluten.
Symptoms
Some people develop symptoms as children. Others do not develop symptoms until adulthood. The severity of symptoms depends on how much of the small intestine is affected.
Adults with the more classic or typical form of the disease experience diarrhea, malnutrition, and weight loss. However, some people have no digestive symptoms at all. About 10% of people with celiac sprue develop a painful, itchy skin rash with small blisters—a disease called dermatitis herpetiformis (see Blistering Diseases: Dermatitis Herpetiformis _http://www.merck.com/mmhe/sec18/ch209/ch209c.html).
In children, symptoms do not appear until foods containing gluten are introduced. Some children experience only mild upset stomach, whereas others develop painful abdominal bloating and have light-colored, unusually foul-smelling, bulky stools (steatorrhea).
The nutritional deficiencies resulting from malabsorption in celiac sprue can cause additional symptoms, which tend to be more prominent in children. Some children develop growth abnormalities, such as short stature. Anemia, causing fatigue and weakness, develops as a result of iron deficiency. Low protein levels in the blood can lead to fluid retention and tissue swelling (edema). Malabsorption of vitamin B12 can lead to nerve damage, causing a pins-and-needles sensation in the arms and legs. Poor calcium absorption results in abnormal bone growth, a higher risk of broken bones, and painful bones and joints. Lack of calcium can also cause tooth discoloration and greater susceptibility to painful tooth decay. Girls with celiac sprue may not have menstrual periods because of a low production of hormones, such as estrogen.
Diagnosis
Doctors suspect the diagnosis when a person has the previously mentioned symptoms. Measurement of the level of specific antibodies produced when a person with celiac sprue consumes gluten is a helpful test. The diagnosis is confirmed by an initial microscopic examination of a biopsy specimen revealing flattened villi of the small intestine and by a subsequent improvement in the lining after the person stops eating foods containing gluten.
Prognosis and Treatment
Although most people do well if they avoid gluten, long-standing celiac sprue can be fatal in a small percentage of people who develop intestinal lymphoma. Whether strictly adhering to a gluten-free diet decreases the risk of long-term complications such as intestinal cancers or lymphoma is not known.
People with celiac sprue must exclude all gluten from their diet, because eating even small amounts may cause symptoms. The response to a gluten-free diet is usually rapid. Once gluten is avoided, the brushlike surface of the small intestine and its absorptive function return to normal. Gluten is so widely used in food products that people with celiac sprue need detailed lists of foods to be avoided and expert advice from a dietitian. Gluten is found, for example, in commercial soups, sauces, ice cream, and hot dogs.
Some people continue to have symptoms even when gluten is avoided. In such cases, either the diagnosis is incorrect or the disease has progressed to a condition called refractory celiac sprue. In refractory celiac sprue, treatment with corticosteroids, such as prednisone, may help. In rare cases, if there is no response to either gluten withdrawal or drug treatment, intravenous feeding is needed. Sometimes children are seriously ill when first diagnosed and need a period of intravenous feeding before starting a gluten-free diet.
Intestinal Lymphangiectasia
(Idiopathic Hypoproteinemia)
Intestinal lymphangiectasia (idiopathic hypoproteinemia) is a disorder in which the lymph vessels supplying the lining of the small intestine become enlarged and obstructed.
*This disorder is the result of improperly formed lymph vessels.
*Diarrhea is the main symptom.
*The diagnosis is based on the results of a biopsy.
*Once the specific cause of the disorder is treated, following a low-fat, high-protein diet and taking supplements can help manage symptoms.
The lymph vessels from the digestive tract carry digested fats that were absorbed by the small intestine. Sometimes, these lymph vessels are improperly formed at birth, causing them to be enlarged. Less commonly, these lymph vessels may enlarge later in life as a result of such conditions as inflammation of the pancreas (pancreatitis) or stiffening of the sac that envelops the heart (constrictive pericarditis). The enlarged lymph vessels carry lymphatic fluid poorly, and the fluid leaks back into the intestine, preventing fat and proteins from being absorbed into the bloodstream.
Symptoms and Diagnosis
A person with intestinal lymphangiectasia has diarrhea. Nausea, vomiting, fatty stools, and abdominal pain may also develop. The person may also have swelling (edema) if lymph vessels elsewhere in the body are blocked.
Levels of protein in the blood are low. The low protein levels result in tissue swelling. The number of lymphocytes in the blood is decreased, and cholesterol levels in the blood may be normal or low.
The diagnosis is established by a biopsy of the small intestine showing enlargement of the lymph vessels. Measurement of a certain protein, called alpha1-antitrypsin, in the stool can indicate the severity of protein loss into the intestines.
Treatment
When intestinal lymphangiectasia is caused by a specific condition, the underlying condition is treated. Symptoms can be helped by eating a low-fat, high-protein diet and taking supplements of calcium, vitamins, and certain triglycerides (medium-chain triglycerides), which are absorbed directly into the blood and not through the lymph vessels.
Lactose Intolerance
Lactose intolerance is the inability to digest the sugar lactose (which is present in all dairy products) because of a deficiency of the digestive enzyme lactase, leading to diarrhea and abdominal cramping.
*Lactose intolerance is caused by a lack of the enzyme lactase.
*Children have diarrhea and may not gain weight, whereas adults have abdominal bloating, cramps, diarrhea, flatulence, nausea, audible bowel sounds (borborygmi), and an urgent need to have a bowel movement.
*The diagnosis is based on recognizing that symptoms occur after a person has consumed dairy products.
*Treatment involves taking supplemental lactase enzymes and avoiding lactose, particularly in dairy products.
Lactose, the predominant sugar found in milk and other dairy products, is broken down by the enzyme lactase, which is produced by the cells in the inner lining of the small intestine. Lactase breaks down lactose, a complex sugar, into its two components, glucose and galactose. These simple sugars are then absorbed into the bloodstream through the intestinal wall. If lactase is lacking, lactose cannot be digested and absorbed. The resulting high concentration of lactose draws fluid into the small intestine, causing diarrhea. The unabsorbed lactose then passes into the large intestine, where it is fermented by bacteria, resulting in flatulence and acidic stool.
Lactase levels are high in infants, permitting them to digest milk. However, in most ethnic groups (80% of blacks and Hispanics, almost 100% of Asians), lactase levels decrease after weaning. These decreased levels mean that older children and adults in these ethnic groups are unable to digest much lactose. However, 80 to 85% of whites of Northwest European descent produce lactase throughout life and are thus able to digest milk and milk products as adults. Therefore, because of the ethnic composition of the U.S. population, it is likely that between 30 million and 50 million people in the United States are lactose intolerant. It is interesting to note that this "intolerance" is really the normal state for more than 75% of the world's population.
Intolerances to other sugars can also occur but are relatively rare. For example, a lack of the enzyme sucrase prevents the sugar sucrose from being absorbed into the bloodstream, and a lack of the enzymes maltase and isomaltase prevents the sugar maltose from being absorbed into the bloodstream.
Symptoms
People with lactose intolerance usually cannot tolerate milk and other dairy products, all of which contain lactose. Some people recognize this early in life and consciously or unconsciously avoid dairy products.
A child who is lactose intolerant has diarrhea and may not gain weight when milk is part of the diet. An adult may have abdominal bloating, cramps, diarrhea, flatulence, nausea, audible bowel sounds (borborygmi), and an urgent need to have a bowel movement between 30 minutes and 2 hours after eating a meal containing lactose. For some people, severe diarrhea may prevent proper absorption of nutrients because they are expelled from the body too quickly. However, the symptoms that result from lactose intolerance are usually mild. In contrast, symptoms that result from malabsorption in such conditions as celiac disease, tropical sprue, and infections of the intestine are more severe.
Diagnosis and Treatment
A doctor suspects lactose intolerance when a person has symptoms after consuming dairy products. If a 3- to 4-week trial period of a diet free of dairy products eliminates the symptoms, the diagnosis is confirmed. Specific tests are rarely necessary.
Lactose intolerance can be controlled through diet by avoiding foods containing lactose, primarily dairy products. Lactase enzymes are available in liquid and tablet forms without a prescription and can be added to milk. Lactose-reduced milk and other products are available at many supermarkets. People who must avoid dairy products should take calcium supplements to prevent calcium deficiency.
Short Bowel Syndrome
Short bowel syndrome is a disorder causing diarrhea and poor absorption of nutrients (malabsorption), which often occurs after surgical removal of a large portion of the small intestine.
*This disorder often occurs after a large part of the small intestine is removed.
*Diarrhea is the main symptom.
*After surgery, people are given food and fluids by vein (intravenously).
*Some people must continue the intravenous feedings for life.
*Drugs such as loperamide Some Trade Names IMODIUM and cholestyramine Some Trade Names QUESTRAN can help reduce diarrhea.
Common reasons for removing a large portion of small intestine are Crohn's disease, a blockage of an artery that supplies blood to a large part of the intestine (mesenteric infarction), inflammation of the intestine caused by radiation (radiation enteritis), cancer, a twisted loop of intestine (volvulus), and birth defects.
Most digestion and absorption of food takes place in the small intestine. The consequences of removing a portion of the small intestine depend on how much is removed and its location. If the middle part (jejunum) is removed, sometimes the last part (ileum) can adapt and absorb more nutrients. If more than about 3 feet (1 yard or 1 meter) of ileum is removed, the remaining small intestine usually cannot adapt. Before adaptation occurs, or if it does not, the intestines have difficulty absorbing many nutrients, including fats, proteins, and vitamins. The intestines also cannot absorb bile acids secreted by the liver, which aid digestion.
Malabsorption causes diarrhea, typically beginning immediately after the surgery. Later, people develop malnutrition and vitamin deficiencies.
Treatment
Immediately after surgery, when diarrhea is typically severe, doctors give intravenous fluids to replace losses and usually also give intravenous feedings. These feedings, called total parenteral nutrition (TPN), contain all necessary nutrients, including proteins, fats, carbohydrates, vitamins, and minerals. As people recover and their stool output lessens, they are slowly given fluids by mouth.
The small intestine is about 12 to 21 feet (4 to 7 yards or meters) in length. People who have had a large amount of small intestine removed (such as those with less than 3.3 feet [100 centimeters] of remaining jejunum) and those who continue to have excessive fluid losses require TPN for life. Others eventually tolerate food by mouth. The recommended diet usually has more fat and protein than carbohydrate. Small, frequent meals are better than fewer, large ones.
People who have diarrhea after meals should take antidiarrheal drugs such as loperamide Some Trade Names IMODIUM 1 hour before eating. Cholestyramine Some Trade Names
QUESTRAN can be taken with meals to reduce diarrhea caused by malabsorption of bile acid. Most people should take supplemental vitamins, calcium, and magnesium. Some people require monthly injections of vitamin B12.
Small-intestine transplantation is an alternative for people who do not adapt to their short bowel and who cannot tolerate long-term TPN.
Tropical Sprue
Tropical sprue is a disorder of unknown cause affecting people living in tropical and subtropical areas who develop abnormalities of the lining of the small intestine, leading to malabsorption and deficiencies of many nutrients.
*This disorder might be caused by an infection, but the real cause is not known.
*Typical symptoms include anemia, light-colored stools, chronic diarrhea, and weight loss.
*A doctor bases the diagnosis on symptoms in a person who lives in or has recently visited one of the areas in which the disorder commonly occurs.
*The antibiotic tetracycline Some Trade Names SUMYCIN treats the disorder.
Tropical sprue occurs chiefly in the Caribbean, southern India, and Southeast Asia. Both natives and visitors may be affected, but children are rarely affected. The cause is unknown, but available evidence suggests an infectious cause.
Symptoms and Diagnosis
Light-colored stools, chronic diarrhea, and weight loss are typical symptoms of tropical sprue. Other symptoms of malabsorption of specific nutrients may also develop. A sore tongue develops from vitamin B2 deficiency. Anemia usually develops as a result of iron, vitamin B12, or folate (folic acid) deficiency, causing fatigue and weakness.
A doctor considers the diagnosis of tropical sprue in a person with anemia and symptoms of malabsorption who lives in or has recently visited one of the areas in which the disorder commonly occurs. X-rays of the small intestine may or may not be abnormal. An endoscopic biopsy (in which a tissue sample is obtained through a flexible tube and examined microscopically) of the small intestine can show some characteristic but not specific abnormalities. A stool sample may be analyzed to exclude parasites or bacteria as a cause.
Treatment
A person suspected of having tropical sprue is treated with an antibiotic. Tetracycline Some Trade Names SUMYCIN is given over several months. Nutritional supplements, especially folate and vitamin B12, are given as needed. Treatment usually results in a full recovery.
Whipple's Disease
(Intestinal Lipodystrophy)
Whipple's disease (intestinal lipodystrophy) is the result of a rare bacterial infection that damages the lining of the small intestine and may involve other organs of the body.
*This disease is caused by a bacterial infection.
*Typical symptoms include diarrhea, inflamed and painful joints, fever, and skin darkening.
*The diagnosis is based on the results of different biopsies.
*If left untreated, the disease is progressive and fatal.
*Antibiotics can eliminate the infection, but the disease can recur.
Whipple's disease affects mainly white men aged 30 to 60. It is caused by an infection with the organism Tropheryma whippelii. The infection usually involves the small intestine but can affect other organs, such as the heart, lung, brain, joints, and eye.
Symptoms
Symptoms of Whipple's disease include diarrhea, inflamed and painful joints, fever, and skin darkening. Severe malabsorption results in weight loss along with fatigue and weakness caused by anemia. Other common symptoms are abdominal pain, cough, and pain when breathing caused by inflammation of the membrane layers covering the lungs (pleura). Fluid may collect in the space between the pleural layers (a condition called pleural effusion—see Pleural Disorders: Pleural Effusion). The lymph nodes may become enlarged. People with Whipple's disease may develop heart murmurs. Confusion, memory loss, or uncontrolled eye movements indicate that the infection has spread to the brain. If left untreated, the disease is progressive and fatal.
Diagnosis and Treatment
A doctor can make the diagnosis of Whipple's disease when an endoscopic biopsy (in which a tissue sample is obtained through a flexible tube and examined microscopically) of the small intestine or a biopsy of an enlarged lymph node shows the bacteria.
Whipple's disease can be cured with antibiotics. Usually people are given ceftriaxone Some Trade Names ROCEPHIN initially by vein, followed by trimethoprim/sulfamethoxazole Some Trade Names BACTRIMSEPTRA taken orally for at least 12 months. Symptoms subside rapidly. Despite initial response to antibiotics, however, the disease can recur.
