Scope of the Diarrhea Problem


Definition of diarrhea

Acute vs. chronic diarrhea

Scope of the problem

The child with acute diarrhea: Care at home, or medical care?

Causes of acute diarrhea in children

Acute diarrhea in children: Principles of management

Medical tests in the child with acute diarrhea

Rehydration of the child with acute diarrhea

Oral rehydration therapy: Rationale and composition

Evaluation and management of the adult with acute diarrhea

Definition of diarrhea

            Diarrhea is a condition characterized by increased frequency and liquidity of bowel movements.1, 2 Patients usually do not refer to frequent non-liquid bowel movements as “diarrhea,” but they may refer to even a single loose stool as “diarrhea.”  

Three bowel movements per day are generally considered the upper end of normal stool output.  The traditional scientific definition of diarrhea emphasizes the weight of stool, with >200 grams/day being considered “diarrhea.”2  However, most of the time it is not practical to actually measure stool output.  Some individuals on high fiber diets can have normal, non-liquid stool output of up to 300 grams/day.


Acute vs. chronic diarrhea

            Diarrhea can be acute or chronic.  “Acute diarrhea” is defined as an episode of diarrhea that lasts 14 days or less.3  Diarrhea that lasts for more than 14 days is considered “persistent,”3 but not all cases of persistent diarrhea last for months or more, or are associated with an underlying chronic disease.  Diarrhea that lasts for 4 weeks or more is considered “chronic.”1, 3 

            The approaches to acute vs. chronic diarrhea differ substantially, in large part because of the different possible causes and complications of acute vs. chronic diarrhea.  Acute diarrhea is generally due to an infection (“acute gastroenteritis,” which can have many causes including viruses and bacteria), and it is self-limited by definition.  Chronic diarrhea can be caused by multiple diseases.  The specific disease determines the characteristics and patterns of the diarrhea.   


Scope of the problem

            Diarrhea is extremely common.  Most cases of diarrhea do not come to medical attention.  Although acute diarrhea is self-limited, it can be severe and can lead to profound dehydration (low fluid level in the body, which can lead to abnormally low blood volume, low blood pressure, and damage to the kidneys, heart, liver, brain, heart, and other major organs).  For this reason, acute

diarrhea remains a major cause of infant mortality around the world.  Over 2 million deaths are attributed to acute diarrhea every year world-wide, most of them in the developing world.4-6  In the United States, up to 375 million episodes of acute diarrhea occur every year, leading to nearly 1 million hospitalizations and 6,000 deaths.6  Chronic diarrhea can cause significant disability. It is estimated that in the United States 5% of adults have chronic diarrhea.7 


The child with acute diarrhea: Care at home, or medical care?

            Care of the child with diarrhea usually begins at home, but caregivers may not always be able to recognize severe dehydration and may not always be able to provide oral rehydration (replenishment of water and salts by mouth).  Several guidelines have been proposed for the management of acute diarrhea in children.4, 8  Most children with acute diarrhea do not have a life-threatening illness, but the first step is to assess whether the child is dangerously ill and/or severely dehydrated, and to consider the possibility of serious underlying disease.


Scope of the Diarrhea problem

  It is recommended that medical care for acute diarrhea be sought whenever an infant appears to be in distress, because infants can become severely dehydrated rather quickly.4  The indications for medical evaluation of children with acute diarrhea include:4

·        Age less than 6 months or weight less than 8 kg (17.6 pounds)

·        History of premature birth; chronic or concurrent medical conditions

·        Fever ≥38ºC (100.4ºF) for age <3 months, or ≥39ºC (102.2ºF) for ages 3-36 months

·        Blood in stool

·        High output (frequent and substantial volume) of diarrhea

·        Persistent vomiting

·        Signs of dehydration (sunken eyes, dry mouth, decreased urine)

·        Irritability, apathy, lethargy

·        Suboptimal response to oral rehydration at home, or inability to provide oral rehydration therapy at home

            Children who are most ill may require admission to the hospital.  Hospital inpatient care is indicated for children if:4

·         Caregivers cannot provide adequate care at home

·         Substantial difficulties exist in administrating oral rehydration therapy (intractable vomiting, oral rehydration solution refusal or inadequate intake)

·         Other possible illnesses complicate the clinical course

·         Oral rehydration solution treatment fails, including worsening diarrhea or dehydration despite adequate volumes

·         Severe dehydration (>9% of body weight) exists

·         Social or logistical concerns exist that might prevent return for further evaluation, if necessary

·         There is a need for close observation (young age, unusual irritability or drowsiness, progressive course of symptoms, or uncertainty of diagnosis)


Causes of acute diarrhea in children

            A wide range of problems4, 8 can present with acute diarrhea in a child, including gastrointestinal infections, most commonly viral, but also bacterial and parasitic; non-gastrointestinal infections, such as meningitis, bacterial sepsis, ear, lung, or urinary infections, in which vomiting may predominate; metabolic problems including diabetes, hyperthyroidism (excess of thyroid hormone), and Addison’s disease (low function of the adrenal glands); antibiotic-associated diarrhea; constipation with overflow; food allergy or intolerance; abnormal absorption of nutrients, as in cystic fibrosis and celiac disease; inflammatory bowel disease (Crohn’s disease or ulcerative colitis); and irritable bowel syndrome.  The latter conditions are more likely to present with chronic diarrhea. 

            When the following signs are present, clinicians should be alerted to look for causes other than acute viral gastroenteritis:8

·        Abdominal pain with tenderness, with or without guarding (tensing of the abdominal wall muscles to “protect” the organs from pressure with the examining hand)

·        Pale skin, jaundice (yellow skin), decreased or absent urine output, bloody diarrhea

·        Sick-appearing child out or proportion to the level of dehydration

·        Shock (abnormally low blood pressure with serious associated consequences)


Acute diarrhea in children: Principles of management

            The key principles for appropriate treatment of acute diarrhea in children emphasize adequate fluid and salt replacement.  The principles are:4

·        Use oral rehydration solution

·        Oral rehydration should be performed rapidly (i.e., over a period of 3-4 hours)

·        Age-appropriate, unrestricted diet is recommended as soon as dehydration is corrected

·        Nursing should be continued for breast-fed infants

·        Diluted formula is not recommended and special formulas are not necessary for formula-fed infants

·        Additional oral rehydration solution should be given to compensate for ongoing losses

·        No unnecessary laboratory tests or medications should be administered


Medical tests in the child with acute diarrhea

            Guidelines suggest that blood tests to measure salts in the blood (electrolytes) and urea are not necessary in children who are not severely dehydrated or sick-appearing, and who will receive oral rehydration (see below).  It is recommended that blood tests be performed to measure urea, creatinine, electrolytes, and bicarbonate in the child with:8

·        Severe dehydration with abnormal circulation

·        Moderate dehydration when a “doughy” feel to the skin may indicate abnormally high concentration of sodium in the blood (due to the greater loss of water relative to the loss of sodium)

·        Moderate dehydration when the presentation suggests something other than a straightforward diarrheal episode

            In children with severe dehydration, blood count and cultures of stool, blood, and urine are also recommended.8  Stool cultures should also be obtained in cases of acute bloody diarrhea (dysentery).4


Rehydration of the child with acute diarrhea

            The management of acute diarrhea rests on restoring and maintaining adequate fluid volume and salt balance (rehydration to correct dehydration, and then maintenance of hydration to compensate for ongoing losses through diarrhea and/or vomiting).4, 8  The amount of fluid that a child has lost is best estimated by the amount of weight loss that the child has experienced.  When weights are not available, the degree of dehydration can be estimated as mild to moderate (3-9% weight loss) when the child has, in order of increasing severity: dry mucous membranes in the mouth, sunken eyes with minimal or no tears, diminished skin turgor (pinched skin in the abdomen takes 1-2 seconds or more to recoil), drowsiness or irritability, and deep breathing.4, 8  Dehydration is severe (>9% weight loss) when the child has increasingly marked signs as described for mild to moderate dehydration, and also has cool, mottled, pale hands and feet, fingers that take more than 2 seconds to “pink up again” when squeezed and released, and, in the extreme, very low blood pressure, rapid heart rate, and abnormal mental status.4, 8

            In most cases, dehydration can be managed with oral rehydration (by mouth).9, 10  It is estimated that for every 25 children treated with oral rehydration, one will not respond and will require intravenous hydration (fluids and electrolytes by vein).10  Oral rehydration therapy consists of the rehydration phase, in which already lost fluids and salts are replaced quickly over 3-4 hours, and a maintenance phase, in which ongoing losses are replaced and nutrition is initiated.4  Families should start oral rehydration as soon as diarrhea begins, and should provide an age-appropriate diet, including more frequent breast or bottle feedings for infants and more fluids for older children.4

            In children with minimal or no dehydration, 1 mL of oral rehydration solution should ideally be given for each gram of stool output, but stool output cannot always be measured.  In this case, 10 mL/kg body weight can be given for each watery stool, and 2 mL/kg body weight for each episode of vomiting.  Alternatively, 60-120 mL (2-4 ounces) can be given for each episode of vomiting or diarrheal stool in children weighing <10 kg (<22 lbs), and 120-240 mL (4-8 ounces) in children weighing >10 kg.  Nutrition should not be restricted.4

            In children with mild to moderate dehydration, their fluid deficit should be estimated (3-9% of body weight) and should be replaced with a total of 50-100 mL/kg body weight of oral rehydration solution given “little and often” over 3-4 hours.4, 8  This may mean trying 5 mL (1 teaspoon) every 1-2 minutes with a dropper, syringe, or teaspoon, and increasing the volume and time interval only if tolerated without vomiting.  If rehydration does not appear to be successful in the first several hours, or if it cannot be accomplished at home, it should be performed by continuous infusion through a nasogastric tube (tube placed through the nose into the stomach), or intravenously.4, 8  After rehydration has been accomplished, further care can be provided at home if the family understands and can provide maintenance hydration and continued feeding as described above, and knows when to return for further medical care (if the child’s condition does not improve or worsens).4

            Severe dehydration with abnormal circulation is a medical emergency.  Severely dehydrated children should receive 20 mL/kg intravenous saline to boost the circulation volume quickly, and very ill children should be admitted to the intensive care unit.4, 8  Additional fluid may be needed.  The blood sodium concentration affects the recommended rate of rehydration.8  If blood sodium concentration is not over 150 mEq/L, then oral rehydration can be given over 3-4 hours by mouth or nasogastric tube.  If blood sodium concentration is over 150 mEq/L, then rehydration that is too rapid can be dangerous, and it is recommended that rehydration be given over 12 hours by mouth, via nasogastric tube or intravenously, as needed, with monitoring of blood tests every 2 hours.


Oral rehydration therapy: Rationale and composition

            Oral rehydration therapy is considered one of the great medical innovations of the 20th century.5 Although the current mortality rate for acute diarrhea is still unacceptably high world-wide, there have been substantial decreases in mortality rates in recent decades that are attributed to campaigns promoting oral rehydration therapy.4

            The normal function of the small intestine includes the ability to handle many liters (in adults, approximately 7 liters) of fluid per day, consisting of ingested food and water as well as salivary and gastrointestinal secretions.  The small intestine absorbs many liters of fluid with nutrients and salts and, in adults, it delivers 1-2 liters to the large intestine (colon), which further absorbs most of this fluid and salts, leading to normal stool output of  <250 mL/day.4  Water passively follows when sodium (table salt is sodium chloride) is absorbed into the body, and specialized channels transport sodium and glucose (a sugar) across the intestinal lining.  This co-transport provides the rationale for oral rehydration solution based on salt, sugar, and water.

            In 2002, the World Health Organization recommended an oral rehydration solution with 75 mmol/L sodium, 75 mmol/L glucose, 20 mmol/L potassium, 65 mmol/L chloride, 30 mmol/L base and total osmolarity of 245 mOsm/L.4  Commercially available oral rehydration solutions in the United States include Rehydralyte, Pedialyte, Endalyte, and CeraLyte, which have similar but not identical composition to the 2002 World Health Organization oral rehydration solution.4  Many commercially available beverages, including sports drinks, are used inappropriately for rehydration.  These beverages have very different compositions from true oral rehydration solutions.  They generally have inadequate salt and sugar content.

            It is possible to make a home-made oral rehydration solution, but because serious errors can occur, standard commercial oral rehydration solutions are recommended if available.4  One level teaspoon of table salt and eight level teaspoons of sugar per liter of water result in a solution with 86 mmol/L of sodium, and one cup of orange juice or two bananas can be added for potassium.6


Evaluation and management of the adult with acute diarrhea

            Most cases of acute diarrhea in adults are due to infections, and the same principles that are outlined for the management of children with acute diarrhea apply in adults.11  Management in adults is aided by the fact that dehydration tends not to become severe as quickly as in infants, and the fact that adults are able to understand their situation and cooperate more with rehydration.  The initial evaluation of adults focuses on assessing the severity of the illness, the need for rehydration, and the identification of likely causes and pathogens.6  Clues in the clinical history include foods eaten, ill contacts, travel, day-care attendance, and specific clinical symptoms.

            Most diarrheal illnesses in adults are viral or self-limited, and often resolve in one day.6  For this reason, stool studies are not necessary in patients who present with a symptom duration of one day, unless they are severely ill or have bloody diarrhea.  Tests for specific pathogens depend on the details of the clinical presentation.6

            As with children, the cornerstone of therapy is oral rehydration unless the patient is severely dehydrated or comatose, in which case intravenous rehydration may be necessary.  The World Health Organization oral rehydration solution, or fluids and salt in soup and crackers are reasonable treatments.6  


Medications in acute diarrhea

            Viruses cause most acute diarrheal illnesses, and most cases of bacterial diarrheal illnesses are self-limited.  Therefore, antibiotics are generally not necessary or useful.  Exceptions exist for immunocompromised hosts, premature infants, or children with underlying disorders.4  Specific treatments are recommended for pathogens associated with acute bloody diarrhea (dysentery) or specific clinical scenarios (e.g., fluoroquinolones for diarrhea in travelers or in community-acquired cases with fever and severe disease, and metronidazole for Clostridium difficile infection or persistent diarrhea with suspected Giardia infection).3, 4, 6

            Most cases of acute diarrhea do not require adjunctive therapy.  The “antidiarrheal” drugs do not treat the underlying causes of diarrhea.  Adsorbents (e.g., kaolin-pectin in Kao-Pectate), antimotility agents (e.g., loperamide [Imodium], diphenoxylate-atropine [Lomotil, Lonox]), antisecretory drugs, toxin binders (e.g., cholestyramine [Questran]) and bismuth subsalicylate (e.g., Pepto-Bismol) are commonly used among older children and adults.4  Because all of these agents can have side effects and there is no compelling evidence of benefit in the acute setting, guidelines recommend against the use of antidiarrheal agents for infants and children with acute gastroenteritis.6, 8


Initial evaluation and management of chronic diarrhea

            Chronic diarrhea has many possible causes, and the evaluation of patients with chronic diarrhea can be complex and challenging.  The clinical history provides important information in determining the likelihood of different diagnoses:1, 2

·          The onset, pattern and duration of diarrhea

·          Travel, possibly contaminated food or water, or contact with ill persons

·          Watery vs. bloody vs. fatty stool

·          Differentiation between diarrhea and pure fecal incontinence (leakage of stool)

·          Presence and characteristics of abdominal pain

·          Weight loss

·          Factors that make the diarrhea worse or better (foods, drugs, stress)

·          Past medical and surgical history, and medications

Physical examination primarily helps determine the volume status of the patient.  Rarely, it can point to specific possible causes of diarrhea.

Blood counts and serum chemistries can suggest inflammation, blood loss, significant fluid and salt losses, or malnutrition.1, 12  Serological tests for celiac disease (a gluten-sensitive enteropathy that is treated with a strict gluten-free diet) should be considered.

If the initial evaluation suggests an obvious cause for diarrhea, then management can be instituted, such as stopping a medication that seems to be causing the diarrhea.  Much of the time, however, further evaluation is necessary.


Possible causes of chronic diarrhea  

            The main causes of chronic diarrhea include chronic infections, inflammatory bowel disease (Crohn’s disease or ulcerative colitis), microscopic (lymphocytic and collagenous) colitis, irritable bowel syndrome, maldigestion (abnormal digestion of nutrients) and malabsorption (abnormal absorption of nutrients), medication side effects, diabetes, and idiopathic secretory diarrhea (watery diarrhea of unknown cause, but possibly due to an infection, since this condition may eventually resolve on its own).2  Less common causes include malignancy, disorders of metabolism, unusual tumors that secrete hormones causing diarrhea, previous operations, bacterial overgrowth, and laxative abuse or factitious diarrhea.  The specific setting, including geographic setting, affects how likely the various diagnoses are, with chronic infections being more common in developing countries.

            Several classification schemes have been proposed for chronic diarrhea, and these are not mutually exclusive.  They include secretory vs. osmotic (in osmotic diarrhea, a non-absorbed molecule keeps fluid in the intestine); small volume (suggestive of colonic disease) vs. large volume (suggestive of small intestine disease); watery vs. fatty vs. bloody (bloody stool suggests inflammation or invasive infection, and fatty stool suggests abnormal digestion or absorption of nutrients).

            Consideration of the clinical details and geographic setting can help determine the type of diarrhea and the likelihood of the different diagnostic possibilities.  This will help determine the most fruitful sequence of additional investigations.


Additional tests in patients with chronic diarrhea

            Analysis of the stool can be very informative in chronic diarrhea.1, 2  There is debate concerning the need to collect stool for 72 hours to quantitate stool weight and fat content, because collection of a single sample can yield much of the important information.1, 12  The quantitative collection can be useful in selected cases.

            Measuring stool serum and potassium concentrations allows calculation of the “osmotic gap,” which is calculated as 290 – 2([Na+] + [K+]) mOsm/kg.  The osmolality of plasma in blood is approximately 290 mOsm/kg, and the intestine cannot affect the concentration of salts in stool in the same way that the kidney can produce dilute or concentrated urine.  Therefore, the osmolality of stool is comparable to that of plasma.  If the osmotic gap is >125 mOsm/kg, this suggests the presence of an unabsorbed molecule that is keeping water in the intestine.  Secretory diarrheas have an osmotic gap <50 mOsm/kg.  Osmotic diarrhea is usually caused by ingestion of magnesium (e.g., magnesium hydroxide in milk of magnesia), or malabsorption of carbohydrate.2, 7

            If stool osmolality is measured, this must be done promptly after stool collection, because bacterial fermentation will cause the osmolality to rise with time.  Low stool osmolality can occur when stool is mixed with water or dilute urine, and high osmolality when it is mixed with concentrated urine.  In both of these situations, the stool collection cannot be considered to be reliable for quantitating volume or calculating the osmolar gap.

            Excess fat in the stool (steatorrhea, or “fatty diarrhea”) suggests abnormal digestion (e.g., pancreatic insufficiency) or absorption (e.g., small bowel mucosal disease).  Stool fat excretion of <7 g/day on a 100 g fat/day diet is considered normal; excretion of 7-14 g/day may be seen simply as a consequence of increased stool output.  However, stool fat excretion of >14 g/day suggests abnormal digestion or absorption.  Qualitative stool testing for fat may help determine whether a quantitative collection should be pursued.  It is important for the patient to have adequate fat intake during determination of stool fat excretion.  Patients may learn to avoid fat if it produces oily, foul, voluminous diarrhea, and testing can be falsely negative if fat is not being ingested.

            Additional tests on the stool include measuring pH, which can suggest carbohydrate malabsorption when pH is <5.6 because malabsorbed carbohydrate is metabolized to fatty acids by colonic bacteria, and looking for fecal leukocytes (white blood cells) that can suggest the presence of inflammation. 

            Further testing should be tailored to the characteristics of the diarrhea and the results of the initial tests.1, 2  In patients with chronic, watery diarrhea with low osmotic gap (secretory diarrhea), the stool should be tested for pathogens that can cause chronic diarrhea.  This includes three exams for ova and parasites, and a test for Giardia stool antigen.  Testing with Clostridium difficile toxin assay should be considered, particularly if there is a history of antibiotic exposure.  Bacteria generally do not cause chronic diarrhea, but Aeromonas andPlesiomonas are exceptions.  Colonoscopy and upper endoscopy with colonic and small bowel biopsies can help establish the diagnosis of microscopic colitis (in which the mucosa appears normal endoscopically but shows microscopic inflammation), or small bowel disease including celiac disease or giardiasis.  Tests for common endocrine conditions including hyperthyroidism are reasonable.  Peptide-secreting tumors are very rare causes of secretory diarrhea, and serum testing for gastrin, calcitonin, vasoactive intestinal peptide and somatostatin, and urine measurement of 5-hydroxyindole acetic acid should be done selectively only in persons with high volume watery diarrhea in whom other tests are unrevealing.  Patients in whom all tests are negative are diagnosed with idiopathic (“idiopathic” means of unknown origin) secretory diarrhea.  This condition may be due to an unidentified infection and it can ultimately prove to be self-limited after many months.

            In patients with bloody or inflammatory diarrhea, colonoscopy and small bowel imaging, if appropriate, should be pursued to evaluate for possible inflammatory bowel disease, and the low probability of a malignancy causing diarrhea with blood.  Stool culture, Clostridium difficile toxin assay, and mucosal biopsy may uncover chronic infections.

            In patients with fatty diarrhea, pancreatic or small bowel disease must be considered.  Pancreatic function testing is not widely available, and its utility is debated.  Radiographic studies to rule out pancreatic structural disease can be considered.  The most useful test for pancreatic exocrine dysfunction, in which not enough digestive enzymes are produced, is probably to undertake a treatment trial with pancreatic enzyme supplementation.  This should consist of prescribing at least 30,000 units of lipase with every meal, and observing whether the diarrhea improves.  Upper endoscopy with multiple small bowel biopsies is the principal test for small bowel mucosal disease.  Investigations for bacterial overgrowth include small bowel aspirate with culture and hydrogen breath testing, but a practical approach is to provide an antibiotic trial and assess the response.


Treatment of chronic diarrhea

            The treatment of chronic diarrhea depends on the ultimate diagnosis that is made after pursuing specific tests.  Chronic infections are treated with the appropriate antimicrobials.  Celiac disease is managed with a strict gluten-free diet.  Treatment of inflammatory bowel disease can include 5-aminosalycilates such as sulfasalazine (Azulfidine) or mesalamine (Asacol, Pentasa), corticosteroids, 6-mercpatopurine or azathioprine, infliximab (Remicade), and emerging biological agents.  Microscopic colitis may respond to a course of bismuth treatment or to budesonide (Entocort), or it can be managed with antidiarrheal medications and 5-aminosalycilates.  Bacterial overgrowth may require rotating courses of antibiotics, which can include amoxicillin/clavulanate, trimethoprim/sulfamethoxazole, doxycycline, metronidazole, and fluoroquinolones, as well as low-dose injections of octreotide, which may improve small bowel motility.

            Functional diarrhea and the diarrhea in irritable bowel syndrome can be treated with antidiarrheals such as loperamide (Imodium) or diphenoxylate/atropine (Lomotil, Lonox).  Idiopathic secretory diarrhea can also be managed with antidiarrheal medications.  Fiber may help firm up the stool.

            Some patients with chronic diarrhea may benefit from treatment with cholestyramine (Questran), a resin that binds bile acids.  Bile acids can stimulate salt and water secretion in the colon.  More potent antidiarrheal treatment with the opiates codeine, paregoric, and tincture of opium may be necessary.  It must be appreciated that paregoric contains 0.4 mg of morphine per 1 mL, compared with 10 mg of morphine per 1 mL in tincture of opium, which is a 25-fold difference.


Special cases: Approach to the traveler with diarrhea, and diarrhea due to Clostridium difficile

            Diarrhea in the traveler requires unique considerations.  First, prevention should be emphasized. Potentially contaminated water and food should be avoided.  Antidiarrheals can be taken to treat diarrhea during travel, but they are not recommended in the presence of fever or bloody diarrhea.  It is reasonable to carry a fluoroquinolone such as ciprofloxacin during travel, to be taken if diarrhea with fever or bleeding develops. Persistent diarrhea in the traveler returning from abroad presents a broad list of diagnostic possibilities, usually infectious or post-infectious.13, 14  Stool testing and endoscopic evaluation with biopsy may be necessary. Specific therapy may be given if particular pathogens are found, or empiric antimicrobial therapy can be tried. In cases without a clear cause and without response to antimicrobial therapy, a post-infectious syndrome is possible, and treatment can be aimed at the symptom of diarrhea with the antidiarrheal agents described previously.13

            Clostridium difficile can be responsible for a wide spectrum of disease from chronic watery diarrhea, to a wasting-type syndrome, to toxic megacolon representing a medical emergency.15, 16  This bacterium has been associated traditionally with antibiotic treatment, which allows it to flourish in the colon while other bacteria are killed and repopulate the colon less successfully.  Clostridium difficile should be suspected as a possible cause of diarrhea in hospitalized or institutionalized patients.  However, recently it has become clear that community-acquired Clostridium difficile infection is increasingly common.  First-line treatment should be with oral metronidazole.  Recurrence can be treated with metronidazole again or oral vancomycin, and subsequent recurrences may require tapered-pulsed vancomycin with or without cholestyramine or the yeastSaccharomyces boulardii.17



            Diarrhea is extremely common.  The causes of acute and chronic diarrhea differ, and this determines the different approach in the acute and chronic setting.  Acute diarrhea is usually infectious and self-limited, but it can cause profound dehydration and even death.  The cornerstone of management is adequate rehydration to replenish fluid and salt losses that have already occurred, and ongoing hydration to compensate for ongoing losses.  

This can usually be accomplished with oral rehydration solution.  Rehydration must be performed with particular attentiveness in children, who can become dangerously dehydrated more quickly and easily than adults, and who often cannot cooperate with rehydration as well as adults.  Chronic diarrhea requires a thoughtful approach, with tests performed in a sequence that is tailored to the specific clinical presentation. Targeted treatments are available for various causes of chronic diarrhea.  When no specific cause can be uncovered, several medications are available for symptomatic treatment.