CHAPTER 68
Diarrhea
(Acute Gastroenteritis)
Presentation
Complaints may range from acute, copious diarrhea that produces shock to concern because an occasional stool is not well formed. Patients with inflammatory diarrhea usually present with fever, tenesmus (the frequent urge to defecate), abdominal pain, and hemoccult-positive stool. These conditions usually cause a more severe form of diarrhea and require more careful assessment and more aggressive treatment. Noninflammatory diarrhea is usually watery, milder, without significant fever, with only mild abdominal cramping, and without blood or leukocytes in the stool. Nausea and vomiting can occur with both forms of diarrhea.
What To Do:
Ask specifically about the frequency of stools, the volume (much liquid implies a defect in absorption in the small bowel, whereas tenesmus producing little more than mucus implies inflammation of the rectosigmoid wall); the character (color, odor, blood, or mucus); and the consistency (water-like or just loose stool). Ask about travel, medications (including antibiotics), residence, daycare attendance, pregnancy status, immunosuppression, consumption of unpasteurized dairy products or undercooked meat or fish, similar symptoms previously, and nocturnal symptoms (rare with functional disease).
Physical examination should focus on signs of moderate or severe dehydration and signs of systemic toxicity. Extracellular volume can be detected by abnormal vital signs, including fever, tachycardia, and postural changes. When dehydration is suspected, obtain a urinalysis and weigh pediatric patients. Any symptoms, fall in blood pressure, or increase in pulse rate of more than 20 beats per minute after standing for a minute suggests hypovolemia. A urine specific gravity of 1.020 or greater also suggests hypovolemia, and ketones of 2 or greater suggest starvation ketosis.
Loss of skin turgor and dryness of mucosal membranes are also signs of dehydration. Physical signs in infants and small children may include ill appearance, sunken fontanel, sunken eyes, decreased tears, dry mouth, cool extremities, delayed capillary refill, and a weak cry.
The presence of peritoneal signs or persistent focal tenderness on abdominal examination may suggest an infection with an invasive enteric pathogen or a cause requiring urgent surgical evaluation and management.
Perform a rectal examination and obtain a sample of stool for occult blood testing and for Wright or Gram staining. If the rectal ampulla is empty, you can still swab the mucosa and may get an even better specimen for stool culture when required. Stool cultures for enteropathogens need only be obtained when there is a suspected community outbreak, involvement of food handlers, special populations (pregnant women, the immunocompromised, the elderly, or those with significant comorbidities who appear ill), temperature greater than 38.5° C, severe or prolonged diarrheal illnesses (generally greater than 1 to 2 weeks in duration), and bloody diarrhea (including Shiga toxin-producing Escherichia coli). A spontaneous specimen is also good.
If the patient has been on antibiotics within the past 2 months, test the stool for Clostridium difficile toxin.
Severe acute diarrhea warrants immediate medical evaluation and possible hospitalization. The criteria for severe acute diarrhea requiring diagnostic evaluation include volume depletion, fever, six or more stools in 24 hours, an illness lasting longer than 48 hours, significant abdominal pain in individuals older than 50 years of age, and diarrhea in special populations (the elderly, pregnant women, or the immunocompromised) The very young and the very old are at greater risk for developing significant fluid loss, with its attendant complications. In patients with inflammatory bowel disease, it is important to send stool studies to help rule out an infectious process, and differentiate this from an inflammatory bowel disease (IBD) “flare.”
If the adult patient is not seriously ill but has a fever higher than 38.5° C (101.3° F), the stool is positive for occult blood, or there are any white blood cells in a 400× field, assume the problem is invasive or inflammatory (e.g., Campylobacter organisms, Salmonella, Shigella, enterohemorrhagic and enteroinvasive E. coli, Entamoeba, ulcerative colitis, and cytotoxic organisms such as Clostridium difficile or Entamoeba histolytica). If there is no risk for C. difficile, and there is no suspicion for enterohemorrhagic E. coli, or fluoroquinolone-resistant Campylobacter infection, prescribe ciprofloxacin (Cipro), 500 mg bid for 3 to 5 days, and schedule follow-up.
Because there are reasonable concerns about a possible association between hemolytic-uremic syndrome and antibiotic administration to children, many authorities believe that children with infectious diarrhea should not be treated empirically; rather, treatment should be based on culture results. Ask the patient to bring a fresh stool sample in a specimen cup at follow-up if the diarrhea persists, in case it needs to be sent for culture or examined for ova and parasites.
If there are no white blood cells on microscopic examination of the stool or the stool is negative for occult blood, assume the diarrhea results from a virus or toxin.
Afebrile adult patients with limited diarrhea require no diagnostic studies or treatment other than fluid and electrolyte replacement. These patients will not benefit from antibiotics and require follow-up only if they have continued diarrhea, abdominal pain, or fever.
Adult patients who feel sick and appear to be dehydrated will benefit from rapid rehydration with IV 0.9% NaCl or lactated Ringer solution (1 to 2 L over an hour for an adult with normal cardiovascular and renal function). Patients who are not vomiting can often be rehydrated by drinking plenty of fluids, such as diluted fruit juices. To replace lost electrolytes, have them eat foods such as saltine crackers, soups, or broth.
Oral rehydration solutions generally are unnecessary in adults younger than 65 years. When an oral rehydration solution is required, do not use “sports drinks” (e.g., Gatorade), because they contain too much sugar and insufficient salt. If oral rehydration solutions (e.g., Rehydralyte) are unavailable, a less ideal substitute can be prepared by adding one-half teaspoon of table salt and one-half teaspoon of baking soda and 4 tablespoons of sugar to 1 L of purified water.
Both classes of diarrhea are best treated with absorbent bulk laxatives, such as methylcellulose (Citrucel), using 1 heaping tablespoon in 8 oz water qd to tid.
Loperamide (Imodium) often limits symptoms to 1 day. It has antimotility and antisecretory effects and is taken as 4 mg after the first loose stool, followed by 2 mg after each subsequent loose stool to a maximum of 16 mg for 2 days. Do not use antimotility agents if there is a suspicion for C. difficile or concern for enterohemorrhagic E. coli, because this may facilitate development of hemolytic uremic syndrome. Antimotility agents are suggested for symptomatic patients with absent or low-grade fever and nonbloody stools.
A chewable loperamide-simethicone combination product has been shown to provide faster and more complete relief of acute nonspecific diarrhea and associated gas-related abdominal discomfort than either of its components provided alone. Loperamide may be used in pregnant women but should not be used at all in children with inflammatory diarrhea or who are younger than 2 years old.
For travelers without signs of invasive or inflammatory diarrhea, give a single dose of ciprofloxacin (Cipro), 500 mg, or norfloxacin (Noroxin), 400 mg PO, to reduce the duration and severity of symptoms. If symptoms persist or the diarrhea is severe or associated with high fever or bloody stools, prescribe ciprofloxacin, 500 mg bid, or norfloxacin, 400 mg twice daily for 3 days. Azithromycin (Zithromax), 10 mg per kg daily for 3 days, can be used for children, or 500 mg daily for 1 to 3 days can be used in pregnant women and for other adults with quinolone-resistant Campylobacter.
Probiotics (Lactobacillus preparations [Culturelle Probiotic, Colon Health Probiotic Caps] and yogurt) can also be used; they have efficacy in nonspecific pediatric diarrhea as well as traveler’s diarrhea.
With infants and small children, oral rehydration therapy should be the main treatment. Enteral rehydration by the oral or nasogastric route is as effective as, if not better than, IV rehydration. Have the parents give an oral rehydration mixture with the goal of replacing the fluid lost. For every 1 cup of diarrhea lost, give a cup of the following recipe:
½ to 1 cup precooked baby rice cereal
2 cups water
¼ tsp salt
Mix the rice cereal, water, and salt together until the mixture thickens but is not too thick to drink. Be sure the ingredients are well mixed. A pinch of the artificial sweetener aspartame (Equal) can be added to make it more palatable. Have the parents give the mixture by spoon often and have them offer the child as much as she will accept (every minute if she will accept it). Instruct the parents that if the child is vomiting, wait 20 minutes and then offer the mixture again in small amounts (½ to 1 tsp) every few minutes. Ondansetron (Zofran ODT) can be used in this situation as an antiemetic. Bananas or other nonsweetened, mashed fruit can help provide potassium.
Alternatively, one can give commercial rehydration fluids, such as Rehydralyte, Ricelyte, or Pedialyte, which are sold in drugstores. When parents are sent home with their children, set a specified amount of time that they should continue to try oral rehydration before coming back to see you. Four to 6 hours is a reasonable time period, depending on the age of the child and the degree of dehydration and illness. They should also come back for a recheck if there are more than 10 to 15 stools, minimal urination, or a general worsening of their child’s appearance.
An alternative to voluntary oral rehydration in infants and children who are moderately dehydrated is the use of rapid nasogastric hydration. Patients can be given standard oral rehydration solution down a nasogastric tube of appropriate size administered at a rate of 50 mL/kg of body weight, delivered over 4 hours.
Infants can become severely dehydrated in short order with viral diarrhea. More severely ill children may benefit from intravenous therapy with normal saline administered at the same rate of 20 to 40 mL/kg over 2 to 4 hours.
Involve the parents in the decision regarding the method of fluid replacement.
During or after diarrhea, children should be given frequent small meals (six or more times a day) and actively encouraged to eat. Nursing infants should continue to breast-feed on demand, and infants and older children should be offered their usual food. Parents should use well-cooked staple starches that can be easily digested, such as rice, corn, potatoes, or noodles in a soft mashed form. Infants should be given a thick porridge or semiliquid pulp. Milk products and cereals are usually well tolerated.
As soon as an adequate degree of rehydration has been achieved, the diet can be advanced quickly as tolerated, and the usual diet should be started at the earliest opportunity.
All patients with severe dehydration may require large amounts of IV fluids and occasionally must be admitted to the hospital.
What Not To Do:
Do not omit the rectal examination, which may disclose a fecal impaction or rectal abscess.
Do not obtain unnecessary stool cultures. It has been estimated that routine stool cultures are positive in only 2% of patients, and most cases of diarrhea in the United States are self limited and will resolve spontaneously. Follow suggestions for sending stool cultures listed above.
Sending stool samples for ova and parasites is usually only recommended for community or daycare outbreaks, patients with ongoing diarrhea (with or without recent travel), patients who are homosexual men, or if there is bloody diarrhea with a paucity of fecal white blood cells.
Do not stop or reduce breast-feeding when a baby has diarrhea. Infants with diarrhea should be breast-fed as often and for as long as they want.
Do not restrict children or adults from having milk or milk products. Despite the potential for lactose intolerance, clinical evidence of lactase deficiency is uncommon, and most individuals can tolerate nonhuman milk without difficulty.
Do not give or recommend sugary drinks such as Gatorade, sweetened commercial fruit drinks, cola drinks, or apple juice if there is significant dehydration. These may cause an osmotic diarrhea and a net loss of fluid. Clear liquids are also not recommended as a substitute for oral rehydration solutions.
Do not confuse influenza with “stomach flu.” Influenza with fever, body aches, cough, and fatigue almost never causes symptoms in the stomach and intestines.
Do not overlook the possibility of acute appendicitis or ischemic bowel disease in those patients with suspicious physical findings or significant risk factors.
Do not have patients use diphenoxylate with atropine (Lomotil). It has central nervous system (CNS) effects that are dangerous if a child accidentally ingests it. It also has unpleasant cholinergic effects.
Do not make the diagnosis of gastroenteritis when the patient is only vomiting. The vomiting may be due to a surgical or nongastrointestinal cause that may possibly be life threatening.
Discussion
Acute infectious gastroenteritis is a common cause of vomiting and diarrhea in the United States. Most patients respond well to symptomatic therapy only. Laboratory testing should be reserved for patients with high fever and bloody or prolonged diarrhea, for the immunocompromised, for suspected cases of antibiotic-associated diarrhea, and for suspected community outbreaks. Empirical antibiotic therapy is generally accepted in adults with fever and hemoccult-positive stool.
Common causes of inflammatory diarrhea include invasive or toxin-producing organisms, such as Campylobacter jejuni, Clostridium difficile, enterohemorrhagic and enteroinvasive E. coli, Shigella sp., nontyphi Salmonella sp., and Entamoeba histolytica. Consider pet reptiles, rodents, and dogs as a possible source of Salmonella and other forms of infectious diarrhea.
Patients with recent antibiotic exposure who present with diarrhea are at risk for antibiotic-associated diarrhea. Most commonly, these patients are afflicted with Clostridium difficile infection, and they should be evaluated specifically for C. difficile toxins A and B. Always suspect C. difficile as the cause of diarrhea in patients who have been in the hospital for longer than 2 weeks, whatever the reason. Also, inpatients who receive proton pump inhibitors and the elderly are at increased risk for C. difficile diarrhea. First-line therapy consists of metronidazole (Flagyl), 500 mg orally 3 times daily for 10 to 14 days, as well as discontinuation of the precipitating antibiotic (if possible).
▪ Viruses commonly cause diarrhea, but it is rarely severe. Associated symptoms are abrupt onset of nausea and abdominal cramps, followed by vomiting or diarrhea. Fevers occur in approximately 50% of affected individuals. Headache, myalgias, upper respiratory symptoms, and abdominal pain are common. Stool studies are negative for fecal leukocytes and blood. Common causes include norovirus, rotavirus, and enteric adenovirus. Other causes of noninflammatory diarrheas include Giardia lamblia, Cryptosporidium parvum, Vibrio cholerae, and enterotoxigenic E. coli.
▪ Travelers’ diarrhea usually begins within the first week of travel and usually resolves without consequence after 3 to 5 days. In most cases, however, symptoms are severe enough to force a change of itinerary or result in confinement to bed. In 1% of cases, hospitalization is necessary.
▪ High-risk regions include the developing countries of Latin America, Africa, Asia, and parts of the Middle East. Areas of intermediate risk include China, southern Europe, Israel, South Africa, Russia, and several Caribbean islands (especially Haiti and the Dominican Republic).
▪ High-risk foods include uncooked vegetables and unpeeled fresh fruit, raw or undercooked meat or seafood (particularly shellfish), and salads. Ice, tap water, and unpasteurized milk carry an increased risk for infection. Safe drinks include bottled carbonated beverages, beer or wine, and boiled or bottled water. Meals eaten in a private home carry reduced risk compared with those eaten in a restaurant. Food from street vendors is particularly risky.
▪ Travelers’ diarrhea often cannot be avoided. If these patients are seen by you, they should be treated like any other patient who presents with diarrhea. For patients who are managed in the pretravel period, chemoprophylaxis is generally discouraged. It is most appropriate to prepare the traveler for prompt self-treatment at the first sign of illness using a combination of an antimotility agent (usually loperamide), about 8 doses/person, and an antibiotic (usually a fluoroquinolone), 6 doses/person, both of which can be obtained prior to departure and carried during travel. Consider azithromycin if the patient is traveling with children or a pregnant adult (see regimen p 255). If symptoms resolve within 24 hours of initiating therapy, no further treatment is necessary. If diarrhea persists after 1 day, treatment should be continued for 1 or 2 more days.
▪ Rifaximin (Xifaxan) is a nonabsorbed oral antibiotic that has been approved for treatment of travelers’ diarrhea, but it is not effective against infections associated with fever or blood in the stool or those caused by Campylobacter. It has fewer adverse effects and drug interactions than do systemic antibiotics, but it cannot be taken during pregnancy. For severe diarrhea, the fluoroquinolones or azithromycin remain the preferred antibiotics.
▪ Acute bloody diarrhea is a frightening symptom that has been associated with E. coli 0157:H7 and other Shiga toxin-producing E. coli infections, illnesses occasionally complicated by the development of hemolytic-uremic syndrome and death. Suspect this in patients who lack high fever and who have abdominal tenderness and pain with bloody diarrhea. It is recommended that stool samples be cultured for patients with acute bloody diarrhea. Antibiotics and antimotility agents should be avoided in patients with suspected or proven infection with enterohemorrhagic E. coli.
▪ It can be useful if acute care practitioners report any suspected infectious outbreaks to public health departments.
▪ Patients with prolonged noninflammatory symptom complexes, especially those who have traveled to endemic areas, may benefit from stool evaluation for parasites. For patients with persistent diarrhea (lasting more than 1 week), an empirical trial of metronidazole or nitazoxanide for a protozoal infection is sometimes considered.
▪ The treatment of diarrhea in immunocompromised patients is essentially the same as that for normal hosts, but such patients may require prolonged courses of antimicrobial therapy and often require subspecialty consultation.
▪ Noninfectious causes of acute diarrhea include inflammatory bowel disease (most often ulcerative colitis, but diarrhea can also be seen with Crohn disease). Symptoms include diarrhea with mucus, rectal bleeding, and abdominal pain.
▪ Medications are another noninfectious cause. The most common medications responsible for acute diarrhea are laxatives; antacids containing calcium or magnesium; colchicines; antibiotics; sorbitol gums; and enteral tube feedings, especially if hypertonic. Diarrhea usually resolves after cessation of the medication.
▪ Other noninfectious causes of diarrhea that need to be considered are pelvic abscess in the area of the rectosigmoid, intestinal ischemia in the elderly, partial small bowel obstruction, obstipation/fecal impaction, or acute appendicitis.
▪ Gastroenteritis is probably the most common diagnosis in missed appendicitis cases. Children with acute appendicitis present with a much higher incidence of diarrhea than those in other age groups, but diarrhea can accompany acute appendicitis at any age. Consider using advanced imaging (ultrasonography or if that fails to be diagnostic, CT scan) early in equivocal cases.
▪ When inflammatory diarrhea is recurrent, suspect a noninfectious cause such as inflammatory bowel disease.
▪ In the pregnant patient who has diarrhea and systemic illness, consider listeriosis.
▪ Ordinary stool cultures only identify Campylobacter, Shigella, Salmonella, Aeromonas, and Yersinia. Aeromonas and Yersinia may be missed on testing unless specifically sought. Testing for other pathogens, such as Vibrio sp., enterohemorrhagic E. coli 0157:H7, and other Shiga toxin-producing bacteria require special media.
▪ Routine laboratory tests (complete blood count [CBC], electrolytes, renal function) are generally neither helpful nor indicated in making a diagnosis. These tests may be useful as indicators of severity of disease, especially in the elderly or the very young, but your clinical impression is more important.
▪ When methylcellulose (Citrucel) is recommended, patients may remind you that they have diarrhea, not constipation. Because these bulk agents absorb water in the gut lumen, however, they can relieve both problems and obviate the rebound constipation often produced by the narcotic and binding agents also used to treat diarrhea.
▪ Older patients medicated for pain or psychosis can develop a fecal impaction, which can also present as diarrhea. Irritable bowel syndrome, food allergy, lactose intolerance, and parasite infestation can produce relapsing diarrhea, but the pattern may only become apparent on follow-up.
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