Diseases

Oral rehydration solutions (ORS) are liquids that contain a carbohydrate (glucose or rice syrup) and electrolyte (sodium, potassium, chloride, and citrate or bicarbonate). Originally, the World Health Organization (WHO) developed the WHO-ORS to rapidly rehydrate victims of the severe diarrheal illness, cholera. The WHO-ORS solution contains glucose and electrolytes. The glucose in the solution is important because it forces the small intestine to quickly absorb the fluid and the electrolytes. The purpose of the electrolytes in the solution is the prevention and treatment of electrolyte deficiencies.In the U.S., convenient, premixed commercial ORS products that are similar to the WHO-ORS are available for rehydration and prevention of dehydration. Examples of these products are Pedialyte, Rehydralyte, Infalyte, and Resol.Most of the commercially available ORS products in the U.S. contain glucose. Infalyte is the only one that contains rice carbohydrate instead of glucose. Most doctors believe that there are no important differences in effectiveness between glucose and rice carbohydrate.

Acute diarrhea: Acute diarrhea usually requires few tests.

• Measurement of blood pressure in the sitting and then then the upright positions can demonstrate orthostatic hypotension (a marked drop in blood pressure) and confirm the presence of dehydration. If moderate or severe dehydration or electrolyte deficiencies are likely, blood electrolytes can be measured.
• Examination of a small amount of stool under the microscope may reveal white blood cells indicating that intestinal inflammation is present and prompting further testing, particularly bacterial cultures of stool and examination of stool for parasites.
• If antibiotics have been taken within the previous two weeks, stool should be tested for the toxin of C. difficile or the bacterial gene that is reasonable for the production of the toxin. It also is possible to culture the C. difficile bacterium.
• Testing stool or blood for viruses is performed only rarely, since there is no specific treatment for the viruses that cause gastroenteritis.
• If there has been recent travel to undeveloped countries or the mountains, stool may be examined under the microscope for Giardia and other parasites.
• There are also immunologic tests that can be done on samples of stool to diagnose infection with Giardia.

Chronic diarrhea: With chronic diarrhea, the focus usually shifts from dehydration and infection (with the exception of Giardia, which occasionally causes chronic infections) to the diagnosis of non-infectious causes of diarrhea. (See the prior discussion of common causes of chronic diarrhea.)

• This may require X-rays of the intestines (upper gastrointestinal series and/or barium enema), or endoscopy (esophagogastroduodenoscopy, EGD, or colonoscopy) with biopsies. Examination of the small intestine via a camera-containing capsule. Specialized small intestinal endoscopy also can be done to visually examine and biopsy the small intestine.
• Fat malabsorption can be diagnosed by measuring the fat in a 72-hour collection of stool. More abbreviated collections are less accurate.
• Sugar malabsorption can be diagnosed by eliminating the offending sugar from the diet or by performing a hydrogen breath test. Hydrogen breath testing also can be used to diagnose bacterial overgrowth of the small intestine.
• An under-active pituitary or adrenal gland and an overactive thyroid gland can be diagnosed by measuring blood levels of cortisol and thyroid hormone, respectively.
• Celiac disease can be diagnosed with blood tests and a biopsy of the small intestine.

The most common cause of acute diarrhea is infection--viral, bacterial, and parasitic. Bacteria also can cause acute food poisoning. A third important cause of acute diarrhea is starting a new medication since many medications can cause diarrhea.

Irritable bowel syndrome: The irritable bowel syndrome (IBS) is a functional cause of diarrhea or constipation. Inflammation does not typically exist in the affected bowel. (Nevertheless, recent information suggests that there MAY be a component of inflammation in IBS.) It may be caused by several different underlying problems, but it is believed that the most common cause is rapid passage of the intestinal contents through the colon.Infectious diseases: A few infectious diseases can cause chronic diarrhea, for example, Giardia lamblia. Patients with AIDS often have chronic infections of their intestines that cause diarrhea.Bacterial overgrowth of the small intestine: Because of small intestinal problems, normal colonic bacteria may spread from the colon and into the small intestine. When they do, they are in a position to digest food that the small intestine has not had time to digest and absorb. The mechanism that leads to the development of diarrhea in bacterial overgrowth is not clear.Post-infectious: Following acute viral, bacterial, or parasitic infections, some individuals develop chronic diarrhea. The cause of this type of diarrhea is not clear, but some of the individuals may have bacterial overgrowth of the small intestine. They also have been found to have abnormalities, either microscopic or biochemical, in biopsies of the intestines that suggest that there may be inflammation. This condition also is referred to as post-infectious IBS.Inflammatory bowel disease (IBD): Crohn's disease and ulcerative colitis, diseases causing inflammation of the small intestine and/or colon, commonly cause chronic diarrhea.Colon cancer: Colon cancer can cause either diarrhea or constipation. If the cancer blocks the passage of stool, it usually causes constipation. Sometimes, however, there is secretion of water behind the blockage, and liquid stool from behind the blockage leaks around the cancer and results in diarrhea. Cancer, particularly in the distal part of the colon, can lead to thin stools. The diarrhea or constipation caused by cancer usually is progressive, that is, becomes progressively worse. Cancer in the rectum can lead to a sense of incomplete evacuation.Severe constipation: By blocking the colon, hardened stool can lead to the same problems as colon cancer, as discussed previously.Carbohydrate (sugar) malabsorption: Carbohydrate or sugar malabsorption is an inability to digest and absorb sugars. The most recognized malabsorption of sugar occurs with lactase deficiency (also known as lactose or milk intolerance) in which milk products containing the milk sugar, lactose, lead to diarrhea. The lactose is not broken up in the intestine because of the absence of an intestinal enzyme, lactase that normally breaks up lactose into its component sugars, galactose, and glucose. Without being broken up, lactose cannot be absorbed into the body. The undigested lactose reaches the colon and pulls water (by osmosis) into the colon. The lactose also is digested by colonic bacteria into gas (hydrogen and methane) as well as chemicals that promote the retention or secretion of fluid in the colon. The result of these events leads to diarrhea. Although lactose is the most common form of sugar malabsorption, other sugars in the diet also may cause diarrhea, including fructose and sorbitol.Fat malabsorption: Malabsorption of fat is the inability to digest or absorb fat. Fat malabsorption may occur because of reduced pancreatic secretions that are necessary for normal digestion of fat (for example, due to pancreatitis or pancreatic cancer) or by diseases of the lining of the small intestine that prevent the absorption of digested fat (for example, celiac disease). Undigested fat enters the last part of the small intestine and colon where bacteria turn it into substances (chemicals) that cause water to be secreted by the small intestine and colon. Passage through the small intestine and colon also may be more rapid when there is malabsorption of fat.Endocrine diseases: Several endocrine diseases (imbalances of hormones) may cause diarrhea, for example, an over-active thyroid gland (hyperthyroidism) and an under-active pituitary or adrenal gland (Addison's disease).Laxative abuse: The abuse of laxatives by individuals who want attention or to lose weight is an occasional cause of chronic diarrhea.

Dehydration occurs when there is excessive loss of fluids and minerals (electrolytes) from the body due to diarrhea, with or without vomiting.

• Dehydration is common among adult patients with acute diarrhea who have large amounts of watery stool, particularly when the intake of fluids is limited by lethargy or is associated with nausea and vomiting.
• It also is common in infants and young children who develop viral gastroenteritis or bacterial infection.
• Patients with mild dehydration may experience only thirst and dry mouth.
• Moderate to severe dehydration may cause orthostatic hypotension with (fainting or light-headedness upon standing) due to a reduced volume of blood, which causes a drop in blood pressure upon standing). A diminished urine output, severe weakness, shock, kidney failure, confusion, acidosis (too much acid in the blood), and coma.

Electrolytes (minerals) are lost with water when diarrhea is prolonged or severe, and mineral or electrolyte deficiencies may occur. The most common deficiencies occur with sodium and potassium. Abnormalities of chloride and bicarbonate also may develop.Finally, there may be irritation of the anus due to the frequent passage of watery stool containing irritating substances.

Many home remedies have been suggested for the treatment of diarrhea; however, few of them have been well-studied. Three that have been studied and appear to be effective are:

• pectin,
• cooked green bananas, and
• probiotics.

Diarrhea can be defined in absolute or relative terms based on either the frequency of bowel movements or the consistency (looseness) of stools.Frequency of bowel movements: Absolute diarrhea is having more bowel movements than normal. Thus, since among healthy individuals the maximum number of daily bowel movements is approximately three, diarrhea can be defined as any number of stools greater than three, although some consider five or more bowel movements to be diarrhea. "Relative diarrhea" is having more bowel movements than usual. Thus, if an individual who usually has one bowel movement each day begins to have two bowel movements each day, then relative diarrhea is present-even though there are not more than three or five bowel movements a day, that is, there is not absolute diarrhea.Consistency of stools: Absolute diarrhea is more difficult to define on the consistency of stool because the consistency of stool can vary considerably in healthy individuals depending on their diets. Thus, individuals who eat large amounts of vegetables will have looser stools than individuals who eat few vegetables and/or fruits. Stools that are liquid or watery are always abnormal and considered diarrheal. Relative diarrhea is easier to define based on the consistency of stool. Thus, an individual who develops looser stools than usual has relative diarrhea--even though the stools may be within the range of normal with respect to consistency.Why does diarrhea develop?With diarrhea, stools usually are looser whether or not the frequency of bowel movements is increased. This looseness of stool--which can vary all the way from slightly soft to watery--is caused by increased water in the stool. During normal digestion, food is kept liquid by the secretion of large amounts of water by the stomach, upper small intestine, pancreas, and gallbladder. Food that is not digested reaches the lower small intestine and colon in liquid form. The lower small intestine and particularly the colon absorb the water, turning the undigested food into a more-or-less solid stool with form. Increased amounts of water in stool can occur if the stomach and/or small intestine secrete too much fluid, the distal small intestine and colon do not absorb enough water, or the undigested, liquid food passes too quickly through the small intestine and colon for enough water to be removed.Another way of looking at the reasons for diarrhea is to divide it into five types.

1. The first is referred to as secretory diarrhea because too much fluid is secreted into the intestine.
2. The second type is referred to as osmotic diarrhea in which small molecules that pass into the colon without being digested and absorbed draw water and electrolytes into the colon and stool.
3. The third type is referred to as motility-related diarrhea in which the intestinal muscles are overactive and transport the intestinal contents through the intestine without enough time for water and electrolytes to be absorbed.
4. The fourth type is unusual. It is best represented by a condition called collagenous colitis. In collagenous colitis, the mechanism of the diarrhea may be the inability of the colon to absorb fluid and electrolytes because of the extensive scarring of the intestinal lining. Inflammation also may play a role.
5. The fifth type of diarrhea is referred to as inflammatory diarrhea and involves more than one mechanism. For example, some viruses, bacteria, and parasites cause increased secretion of fluid, either by invading and inflaming the lining of the small intestine (inflammation stimulates the lining to secrete fluid) or by producing toxins (chemicals) that also stimulate the lining to secrete fluid but without causing inflammation. Inflammation of the small intestine and/or colon from bacteria or from non-bacterial ileitis/colitis can increase the rapidity with which food passes through the intestines, reducing the time that is available for absorbing water.

Diarrhea generally is divided into two types, acute and chronic.

1. Acute diarrhea lasts from a few days up to a week.
2. Chronic diarrhea can be defined in several ways, but usually lasts more than three weeks.

It is important to distinguish between acute and chronic diarrhea because they usually have different causes, require different diagnostic tests, and require different treatment.

Diarrhea is an increase in the frequency of bowel movements or a decrease in the form of stool (greater looseness of stool). Although changes in frequency of bowel movements and looseness of stools can vary independently of each other, changes often occur in both.Diarrhea needs to be distinguished from four other conditions. Although these conditions may accompany diarrhea, they often have different causes and different treatments than diarrhea. These other conditions are:

1. Incontinence of stool, which is the inability to control (delay) bowel movements until an appropriate time, for example, until one can get to the toilet
2. Rectal urgency, which is a sudden urge to have a bowel movement that is so strong that if a toilet is not immediately available there will be incontinence
3. Incomplete evacuation, which is a sensation that another bowel movement is necessary soon after a bowel movement, yet there is difficulty passing further stool the second time
4. Bowel movements immediately after eating a meal

During mild cases of diarrhea, diluted fruit juices, soft drinks containing sugar, sports drinks such as Gatorade, and water can be used to prevent dehydration. Caffeine and lactose containing dairy products should be temporarily avoided since they can aggravate diarrhea, the latter primarily in individuals with transient lactose intolerance. If there is no nausea and vomiting, solid foods should be continued. Foods that usually are well tolerated during a diarrheal illness include rice, cereal, bananas, potatoes, and lactose-free products.Oral rehydration solutions can be used for moderately severe diarrhea that is accompanied by dehydration in children older than 10 years of age and in adults. These solutions are given at 50 ml/kg over 4-6 hours for mild dehydration or 100 ml/kg over 6 hours for moderate dehydration. After rehydration, the oral rehydration solution can be used to maintain hydration at 100 ml to 200 ml/kg over 24 hours until the diarrhea stops. Directions on the solution label usually state the amounts that are appropriate. After rehydration, older children and adults should resume solid food as soon as any nausea and vomiting subside. Solid food should begin with rice, cereal, bananas, potatoes, and lactose free and low fat products. The variety of foods can be expanded as the diarrhea subsides.

Most acute diarrhea in infants and young children is due to viral gastroenteritis and is usually short-lived. Antibiotics are not routinely prescribed for viral gastroenteritis. However, fever, vomiting, and loose stools can be symptoms of other childhood infections such as otitis media (infection of the middle ear), pneumonia, bladder infection, sepsis (bacterial infection in the blood) and meningitis. These illnesses may require early antibiotic treatment.Infants with acute diarrhea also can quickly become severely dehydrated and therefore need early rehydration. For these reasons, sick infants with diarrhea should be evaluated by their pediatricians to identify and treat underlying infections as well as to provide instructions on the proper use of oral rehydration products.Infants with moderate to severe dehydration usually are treated with intravenous fluids in the hospital. The pediatrician may decide to treat infants who are mildly dehydrated due to viral gastroenteritis at home with oral rehydration solutions.Infants that are breastfed or formula-fed should continue to receive breast milk during the rehydration phase of their illness if not prevented by vomiting. During, and for a short time after recovering from viral gastroenteritis, babies can be lactose intolerant due to a temporary deficiency of the enzyme, lactase (necessary to digest the lactose in milk) in the small intestine. Infants with lactose intolerance can develop worsening diarrhea and cramps when dairy products are introduced. Therefore, after rehydration with oral rehydration solutions, an undiluted lactose-free formula and diluted juices are recommended. Milk products can be gradually increased as the infant improves.

AbsorbentsAbsorbents are compounds that absorb water. Absorbents that are taken orally bind water in the small intestine and colon and make diarrheal stools less watery. They also may bind toxic chemicals produced by bacteria that cause the small intestine to secrete fluid; however, the importance of toxin binding in reducing diarrhea is unclear.The two main absorbents are attapulgite (a naturally occurring complex mineral) and polycarbophil (a fiber) both available without prescriptions. Psyllium, another absorbent has been used for mild diarrhea, but is primarily used for constipation.Examples of products containing attapulgite are:

• Donnagel,
• Rheaban,
• Kaopectate Advanced Formula,
• Parepectolin, and
• Diasorb.

Examples of products containing polycarbophil are:

• Equalactin,
• Konsyl Daily Fiber Therapy,
• Mitrolan, and
• Polycarb.

Products containing polycarbophil have been used to treat both diarrhea and constipation. Attapulgite and polycarbophil remain in the intestine and, therefore, have no side effects outside of the gastrointestinal tract. They may occasionally cause constipation and bloating. One concern is that absorbents also can bind medications and interfere with their absorption into the body. For this reason, it often is recommended that medications and absorbents be taken several hours apart so that they are physically separated within the intestines.Anti-motility medicationsAnti-motility medications are drugs that relax the muscles of the small intestine and/or the colon. Relaxation results in slower flow of intestinal contents. Slower flow allows more time for water to be absorbed from the intestine and colon and reduces the water content of stool. Cramps, due to spasm of the intestinal muscles, also are relieved by the muscular relaxation.The two main anti-motility medications are loperamide (Imodium), which is available without a prescription, and diphenoxylate (Lomotil), which requires a prescription. Both medications are related to opiates (for example, codeine) but neither has the pain-relieving effects of opiates.Loperamide (Imodium), though related to opiates, does not cause addiction.Diphenoxylate is a man-made medication that at high doses can be addictive because of its opiate-like, euphoric (mood-elevating) effects. In order to prevent abuse of diphenoxylate and addiction, a second medication, atropine, is added to loperamide in Lomotil. If too much Lomotil is ingested, unpleasant side effects from too much atropine will occur.Loperamide and diphenoxylate are safe and well-tolerated. There are some precautions, however, that should be observed.

• Anti-motility medications should not be used without a doctor's guidance to treat diarrhea caused by moderate or severe ulcerative colitis, C. difficile colitis, and intestinal infections by bacteria that invade the intestine (for example, Shigella). Their use may lead to more serious inflammation and prolong the infections.
• Diphenoxylate can cause drowsiness or dizziness, and caution should be used if driving or if tasks that require alertness and coordination are required.
• Anti-motility medications should not be used in children younger than two years of age.
• Most unimportant, acute diarrhea should improve within 72 hours. If symptoms do not improve or if they worsen, a doctor should be consulted before continuing treatment with anti-motility medications.

Bismuth compoundsMany bismuth-containing preparations are available around the world. Bismuth subsalicylate (Pepto-Bismol) is available in the US. It contains two potentially active ingredients, bismuth and salicylate (aspirin). It is not clear how effective bismuth compounds are, except in traveler's diarrhea and the treatment of H. pylori infection of the stomach where they have been shown to be effective. It also is not clear how bismuth subsalicylate might work. It is thought to have some antibiotic-like properties that affect bacteria that cause diarrhea. The salicylate is anti-inflammatory and could reduce secretion of water by reducing inflammation. Bismuth also might directly reduce the secretion of water by the intestine.Pepto-Bismol is well-tolerated. Minor side effects include darkening of the stool and tongue. Several precautions that should be observed when using Pepto-Bismol.

• Since it contains salicylate, a chemical related to aspirin (acetyl salicylate), patients who are allergic to aspirin should not take Pepto-Bismol.
• Pepto-Bismol should not be used with other aspirin-containing medications since too much aspirin may be ingested and lead to aspirin toxicity, the most common manifestation of which is ringing in the ears.
• The salicylate in Pepto-Bismol, similar to aspirin, can accentuate the effects of anticoagulants, particularly warfarin (Coumadin), and lead to excessive bleeding. It also may cause abnormal bleeding in people who have a tendency to bleed because of genetic disorders or underlying diseases, for example, cirrhosis that also may cause abnormal bleeding.
• The salicylate in Pepto-Bismol can aggravate stomach and duodenal ulcer disease like asiprin.
• Pepto-Bismol and salicylate-containing products should not be given to children and teenagers with chickenpox, influenza, and other viral infections because they may cause Reye's syndrome. Reye's syndrome is a serious illness affecting primarily the liver and brain that can lead to liver failure and coma, with a mortality rate of at least 20%.
• Pepto-Bismol should not be given to infants and children younger than two years of age.

The symptoms that are associated with diarrhea depend on the cause and type of diarrhea.

• If there is a large secretory component to the diarrhea the bowel movements are frequent and watery. Pain is not common, and there are no signs of inflammation.
• Similarly, an osmotic diarrhea is watery, but its main characteristic is that once ingestion of food stops (which would include the offending dietary food or substance that is not digested or absorbed) the diarrhea stops.
• Motility related diarrhea is more likely to be associated with cramping abdominal pain.
• Inflammatory diarrhea often is associated with crampy abdominal pain as well as signs of inflammation, for example, fever, and abdominal tenderness. It also may be associated with intestinal bleeding, either with visible blood in the stool or invisible blood that only is detected by testing the stool for blood.
• Although one might expect the diarrhea of collagenous colitis to be painless (since diarrhea is believed to be due to poor absorption of fluid and electrolytes), in fact, it is frequently associated with abdominal pain, suggesting that there is more to collagenous colitis than a failure to absorb fluid and electrolytes.

Most episodes of diarrhea are acute and of short duration and do not require antibiotics. Antibiotics are not even necessary for the most common bacterial infections that cause diarrhea.Antibiotics, however, often are used when

• patients have more severe and persistent diarrhea,
• patients have additional debilitating diseases such as heart failure, lung disease, and AIDS,
• stool examination and testing discloses parasites, more serious bacterial infections (for example, Shigella), or C. difficile, and
• traveler's diarrhea.

Most episodes of diarrhea are mild and of short duration and do not need to be brought to the attention of a doctor. The doctor should be consulted when there is:

• High fever (temperature greater than 101 F or 38.3 C
• Moderate or severe abdominal pain or tenderness
• Bloody diarrhea that suggests severe intestinal inflammation
• Diarrhea in persons with serious underlying illness for whom dehydration may have more serious consequences, for example, persons with diabetes, heart disease, and AIDS
• Severe diarrhea that shows no improvement after 48 hours.
• Moderate or severe dehydration
• Prolonged vomiting that prevents intake of fluids orally
• Acute diarrhea in pregnant women because of concern for the health of the fetus
• Diarrhea that occurs during or immediately after completing a course of antibiotics because the diarrhea may represent antibiotic-associated infection with C. difficile that requires treatment
• Diarrhea after returning from developing countries or from camping in the mountains because there may be infection with Giardia (for which there is treatment)
• Diarrhea that develops in patients with chronic intestinal diseases such as colitis, or Crohn's disease because the diarrhea may represent worsening of the underlying disease or a complication of the disease, both requiring treatment
• Acute diarrhea in an infant or young child in order to ensure the appropriate use of oral liquids (type, amount, and rate), to prevent or treat dehydration, and to prevent complications of inappropriate use of liquids such as seizures and abnormal blood electrolytes (minerals)
• Chronic diarrhea

Gastroenterologists are the specialists who usually manage patients with diarrhea and pursue the diagnosis of its cause, particularly when the diarrhea is chronic.