Disorders of the gastrointestinal tract

General therapy for diarrhea

Diet. If nausea and vomiting do not prevent eating, adjust the diet based on patient preference and tolerance:

• 1.

  When diarrhea is severe, stick to clear fluids such as mineral water, soda, Kool-Aid, or broth. Electrolyte-containing sports beverages are fine. Apple and grape juices are good, but orange, tomato, pineapple, and grapefruit juices might irritate the stomach. Avoid milk products, tea, coffee, raw fruits and vegetables, and fatty foods. Do not take aspirin.

• 2.

  As soon as there is improvement (less frequent bowel movements, decreased cramping, increased appetite), begin solid foods, starting with broth, crackers, toast, gelatin, and hard-boiled eggs or any substantial foods preferred by the victim.

• 3.

  As the diarrhea subsides, add applesauce, mashed bananas, rice, boiled or baked potatoes, and plain pasta.

• 4.

  When stools begin to firm up, add cooked lean meat, cooked vegetables, yogurt, and cottage cheese. Avoid alcohol, spicy foods, and stewed fruit.

Dehydration can be estimated as follows:

• 1.

  Mild dehydration: Thirst, dry mucous membranes (mouth, eyes), dry armpits, dark urine, decreased sweating, normal pulse rate.

• 2.

  Moderate dehydration: The above plus sunken eyes, doughy skin, weakness, scant darkened urine, rapid and weak pulse rate.

• 3.

  Severe dehydration: The above plus altered mental status, elevated body temperature, no urine, no tears, no sweating, collapse, shock (see page 70).

• 4.

  In a baby, dehydration manifests as dry diaper (decreased urine output), sunken eyes, sunken “soft spot” (fontanel) on the top of the head, dry tongue and mouth, rapid pulse, poor skin color (blue or pale), lethargy (“floppy baby”), and fast breathing. Normal vital signs for children can be found on page 40.

Fluid replacement

If fluid losses are significant (more than five bowel movements per day), begin to replace liquids as soon as you can. When in doubt as to the severity of dehydration, begin to replace liquids. If only fruit juice (without supplementation) is available, remember to cut it to half strength with water. Otherwise, the sugar content will be too high and might contribute to continued diarrhea. Estimation techniques to measure powdered ingredients (such as a “pinch” of table salt) are notoriously inaccurate and can even be dangerous if you add excessive amounts; use a proper measuring implement whenever possible. If nausea and vomiting are present to a degree sufficient to inhibit or prevent oral rehydration, consider administration of an antiemetic drug, such as ondansetron (Zofran: adult dose 4 mg oral dissolving tablet; pediatric dose 0.15 mg/kg body weight of the oral dissolving tablet every 8 hours). In adults, inhaling isopropyl alcohol fumes from an alcohol-saturated pad (“wipe”) held ½ to 1 inch from the nose, with or without taking ondansetron, has been reported effective to relieve nausea.

• 1.

  Mild diarrhea/dehydration: Drink soda water, clear juices, broth, and electrolyte-containing sports beverages. Try to replace each diarrheal stool with 10 mL of oral rehydration salts (ORS) per 1 kg (2.2 lb) of body weight. If the child is vomiting, try to replace each episode of vomiting with 2 mL of ORS per 1 kg (2.2 lb) of body weight. Give ORS or any other replacement fluid slowly at first so that it is tolerated without vomiting. For small children, this can be a teaspoonful at a time; for adults it will be sips from a cup (try for two tablespoons [30 mL] every 5 minutes). If the patient vomits, then wait for 10 minutes and try once again to give ORS, but more slowly. Children will sometimes turn their noses at the taste of ORS. You might be able to get them rehydrated by offering preferred beverages, such as one-half strength apple juice.

• 2.

  Moderate diarrhea/dehydration: Drink diluted (by half, with water) electrolyte-containing sports beverages, mineral water (bottled), or a homemade solution consisting of 1 quart or liter of disinfected water (or orange juice) plus ½ to 1 teaspoon (1.3 to 2.5 mL) of sodium chloride (table salt), ½ teaspoon of sodium bicarbonate (baking soda), ¼ teaspoon (0.6 mL) of potassium chloride (salt substitute), and glucose (6 to 8 teaspoons [30 to 40 mL] of table sugar, or 1 to 2 tablespoons [15 to 30 mL] of honey). Take care not to over sweeten (i.e., do not exceed 2% to 2.5% glucose) the solution with sugar, because this might worsen the diarrhea; too high a sugar concentration inhibits water absorption through the gastrointestinal tract. Each quart of this “home brew” should be alternated with ½ to 1 quart of plain disinfected water. Try to replace fluid losses at least every 2 hours.

  • ORS that meet World Health Organization standards are available in a dry mix; use one packet per quart (liter) of water. One packet contains sodium chloride 3.5 g, potassium chloride 1.5 g, glucose 20 g, and trisodium citrate 2.9 g (or sodium bicarbonate 2.5 g). CeraLyte 70 ORS are based on a rice solution. One packet is mixed with a quart (liter) of water. After the solution is prepared, it should be consumed or discarded within 12 hours if kept at room temperature or 24 hours if kept refrigerated. Rice-based electrolyte-containing drinks, such as CeraSport, are likely more effective than water in replacing fluid losses. Other ORS products available over-the-counter include Pedialyte, Enfalyte, Naturalyte, and Rehydralyte. Elete is an electrolyte additive (to water) that contains sodium, chloride, potassium, zinc, and magnesium, but no glucose or carbohydrate.

  • In greater detail, try to get the victim to ingest a quart per hour until the frequency of urination begins to increase and the urine color becomes light-colored. To begin, start with small (e.g., 5 mL or 1 teaspoon) amounts every 1 to 2 minutes, to avoid collection of a large amount of fluid in the stomach that might cause vomiting. A child should be given 1½ oz (44 mL) of ORS per pound (0.45 kg) of body weight over the first 4 hours, then 1 oz (30 mL) of ORS per pound of body weight per 8-hour period until the diarrhea resolves. Another estimate of fluid replacement for children is 100 mL (approximately 3 oz) of fluid per significant loose bowel movement. For an infant with diarrhea, decrease the amount of milk in the diet and trial Pedialyte or another ORS substitute. Sweetened carbonated beverages (soda pop) are not good replacement fluids, because they contain too much sugar and little or no sodium and potassium. If the child is breast-fed, keep nursing (offer the breast more often). If the child is formula-fed, use ORS for 12 to 24 hours, and then try switching back to formula. If the diarrhea persists, switch back to ORS for another cycle. It is important to continue to provide nourishment with food (and calories) to children with diarrhea, not fluid alone. Avoid foods high in simple sugars (including tea, juices, and soft drinks). Try complex carbohydrates (rice, wheat, potatoes, bread, cereals), yogurt, lean meat, fruits, and vegetables.

  • If premeasured salts are not available with which to supplement water, you can alternate glasses of the following two fluids, as recommended by the U.S. Public Health Service:

    • Glass one—8 oz fruit juice with ¼ teaspoon (a “pinch”) table salt and ½ teaspoon honey or corn syrup (237 mL juice, 1.3 mL table salt, 2.5 mL honey or corn syrup)

    • Glass two—8 oz disinfected water with ¼ teaspoon baking soda (sodium bicarbonate) (237 mL water, 1.3 mL baking soda)

• 3.

  Severe diarrhea/dehydration: Same as moderate. After a certain point, as with cholera, intravenous hydration can be lifesaving. See a physician as soon as possible.

Rehydration enema. When it is impossible to administer oral fluids, a rehydration enema can be lifesaving. A Camelbak-style hydration system can be used with the mouthpiece (“bitepiece”) removed in such a way as to eliminate sharp edges. Squeeze all the air out of the fluid reservoir so that all that remains is liquid. Position the patient on their left side. Lightly lubricate the anus and tube with a water or petrolatum-based lubricant, using a very gentle tube insertion of no more than 4 to 7 inches (10 to 17 cm) to administer 1 pint of an enema solution of 1 liter of ORS or body temperature disinfected water mixed with 5 tablespoons of sugar and 1 tablespoon of salt. If these are not available, use plain water. Have the person try to relax and retain the fluid for as long as possible before evacuating the residual. You might need to use tape to keep the tube in place and the buttock cheeks tight. Use gravity to administer the fluid—do not force it in by squeezing the bag. Try to administer 1 pint every 1 to 2 hours until the person is producing light-colored urine or is able to tolerate oral liquids.

Antimotility (decreased bowel activity) drugs . If fever, severe cramping, and bloody diarrhea are absent, it is safe to use antimotility drugs. They should be immediately discontinued if diarrhea lasts for more than 48 hours. If diarrhea lasts longer than 3 days, if the victim has a fever greater than 101°F (38.3°C), if they cannot keep liquids down because of vomiting, if there is blood in or on the stool, if the abdomen becomes swollen, or if there is no significant pain relief after 24 hours, seek a physician immediately.

The antimotility drug of choice is loperamide (Imodium A-D). The initial adult dose is 4 mg (two 2 mg capsules, or 4 teaspoons [20 mL] of the liquid), followed by 2 mg after each loose bowel movement, not to exceed 16 mg (8 capsules) per day or 2 consecutive days of administration. With uncomplicated watery diarrhea (no fever or blood in stools), this drug can be given to children aged 2 years and older. Give children a dose of 0.2 mg/kg (2.2 lb) of body weight every 6 hours. The liquid preparation contains 1 mg/teaspoon (5 mL). Be aware that higher than recommended doses of loperamide can lead to dangerously abnormal heart rhythms.

For adults, diphenoxylate (Lomotil) is an alternative, but has side effects of dry mouth and urinary retention. Pepto-Bismol is another, less effective choice (see page 493).

Kaopectate (kaolin plus pectin) is of limited value. It does not shorten the course of diarrheal illness and acts only to add a little consistency to stools. Lactobacillus preparations (acidophilus beverages or yogurt) do not shorten the course of acute diarrheal illness, but might be useful to repopulate the gastrointestinal tract with normal bacteria after a severe bout of diarrhea or administration of antibiotics used to treat diarrhea.

Outside the U.S., drugs that have been recommended to treat diarrhea in the absence of a specific diagnosis include chloramphenicol (Chloromycetin), Entero-Vioform, MexaForm, Intestopan, clioquinol, and iodoquinol. This might be dangerous, because these drugs can have adverse direct effects or side effects. Therefore, this approach should not be taken without a specific diagnosis for which these drugs are felt to be indicated.

Antibiotics. These should be used if diarrhea is moderate to severe (more than eight bowel movements per day), particularly if it is bloody and associated with severe cramping, vomiting, and fever. Antibiotics should not be used if E. coli O157:H7 is suspected (see page 236). They should not be used for mild traveler-associated diarrhea.

If cholera is suspected, administer azithromycin (adults 1 g single dose; children 20 mg/kg [2.2 lb] body weight single dose). If azithromycin is not available, administer ciprofloxacin (adults 1 g single dose; children 15 mg/kg [2.2 lb] body weight twice daily for 3 days). Another alternative for adults is doxycycline 300 mg in a single dose. Treatment for cholera is largely supportive care, but the duration of cholera caused by Vibrio cholerae might be shortened by adding antibiotics. Other beneficial effects of antibiotic administration for cholera include diminished rate of “purging” diarrhea (often in the form of profound “rice water” stools), shortened period of being infectious, and less requirement for rehydration. The antibiotic is most effectively given after rehydration therapy has begun to take effect and vomiting diminished to the point that the antibiotic can be retained. Resistant strains are very common; for instance, in Bangladesh, cholera is resistant to tetracycline, erythromycin, and trimethoprim–sulfamethoxazole.

If cholera is NOT suspected, administer azithromycin (1 g single dose or 500 mg per day for 3 days). If this fails to improve the situation within 24 hours, administer trimethoprim–sulfamethoxazole (Bactrim or Septra) one double-strength pill twice a day, or ciprofloxacin (Cipro) 500 mg twice a day for 3 days. (See fluoroquinolone antibacterial drugs precaution on page 498.) These will treat Escherichia coli and Shigella , might be of use for Salmonella , and will not adversely affect the course of viral, Staphylococcus, or Campylobacter infections. Enteric fever caused by Salmonella typhi (typhoid fever) is best treated in adults with ciprofloxacin. However, this germ is becoming resistant to many antibiotics. For instance, in Pakistan, it might only respond to azithryomycin and the carbapenem class of antibiotics.

Alternative drugs include norfloxacin (Noroxin) 400 mg twice a day for 3 days, ofloxacin (Floxin) 200 or 300 mg twice a day for 3 days, or fleroxacin 400 mg once a day for 3 days. Another alternative drug is doxycycline (Vibramycin) 100 mg twice a day. Children younger than 12 years of age should not be given doxycycline, because it might cause discoloration of the permanent teeth. Because ciprofloxacin can affect bone growth in children, it should be given only to adults, with the precaution given previously that it is becoming a drug of last resort because of side effects upon tendon-like tissue.

If the clinical picture clearly points to Giardia lamblia (see page 236), administer tinidazole 2 gm one dose or metronidazole (Flagyl) 250 mg three times a day for 7 days. A woman who is possibly pregnant should not use this drug except under the advice of her physician.

Sometimes diarrhea appears as a complication of antibiotic administration. This is called Clostridioides difficile– associated disease, antibiotic-associated diarrhea, or antibiotic-associated colitis. It is caused by infection with the organism C. difficile , which thrives in the bowel after the normal germs are killed by the initial antibiotic therapy. Another causative factor might be administration of a proton pump inhibitor drug, which lowers gastric acid. This helps C. difficile to survive and therefore be able to elaborate its toxin. The affliction can be diagnosed by testing stool for the germ or the toxins it creates. Therapy for persons aged 18 years of age or older against C. difficile is vancomycin 125 mg by mouth four times a day or fidaxomycin 200 mg by mouth for 10 days. If neither of these is available, use metronidazole (Flagyl) 500 mg by mouth three times a day or 250 mg by mouth four times a day. It is important to note that C. difficile spores are not destroyed by disinfectant hand gels; thus handwashing remains extremely important to prevent the spread of this infectious organism. C. difficile infection is also observed in travelers without any history of prior antibiotic use.

Probiotics are harmless microorganisms (mostly bacteria and yeast) that are thought to provide health benefits. Examples include Lactobacillus rhamnosus ( casei ) and reuteri , which are found in certain yogurt products, and CULTURELLE, which is an all-natural dietary supplement containing the probiotic L. rhamnosus strain GG (LGG). Probiotics, therefore, are a class of “friendly” bacteria that live in the digestive tract, where they help to restore and maintain a healthy balance of “good” versus “bad” bacteria. They might be useful in helping the bowel recover its normal function if ingested during and after a bout of diarrhea, particularly if antibiotics have been used to treat the victim. They might also slightly shorten the duration and symptoms of acute infectious watery diarrhea and improve the condition of a person who suffers C. difficile infection after being treated with an antibiotic for gastroenteric infection.

Recovery diet after diarrhea. After suffering from diarrhea, the recovering person will have a return of appetite and might wish to make up for lost time. That temptation to overeat should be resisted by using a “recovery diet” that progresses from easily digested foods such as crackers, gelatin, and “simple” carbohydrates; to eggs, potatoes, rice, bananas, and cooked vegetables; to dairy, meat, fatty foods, and raw fruits and vegetables. How quickly one progresses back to a normal diet depends on the reaction to the diet. If there is diminished gastroenteric upset accompanied by the presence of formed stools, then the diet can be advanced. One common problem that persons who have suffered from diarrhea might cause themselves is avoiding fiber and perceived irritating foods for too long to the extent that they now become constipated. After infectious diarrhea is resolved, one should optimally be able to get back to a normal diet and bowel pattern within a few days.

Another possible sequel to a bout of infectious diarrhea is lactose intolerance, generally caused by deficiency or ineffectiveness of lactase, which breaks lactose down into components that can be absorbed. Symptoms include abdominal pain, bloating, diarrhea, and flatulence. Following a bout of infectious diarrhea, it makes sense to eat lactose-free foods or low-lactose dairy foods (e.g., milk, yogurt, cottage cheese, butter) in small amounts.

Traveler’s diarrhea

Traveler’s diarrhea (TD; “turista,” “Kathmandu quickstep,” “Montezuma’s revenge,” “Delhi belly,” “Aztec two-step,” “Hong Kong dog,” and many other synonyms) is frequent, loose bowel movements (three or more loose stools in a 24-hour period) associated with one or more of nausea, vomiting, abdominal cramps, fever, urge to defecate, cramping and straining with defecation, or bloody or mucus-laden stools. It is caused by waterborne or food-borne pathogens, most commonly produced by forms of the bacterium E. coli , which is introduced into the diet as a fecal contaminant in water or on food. Someone has described it as “stool that fits the shape of the container.” When caused by E. coli , symptoms usually occur 12 to 36 hours after ingesting the bacteria and include the gradual or sudden onset of frequent (four to five per day) loose or watery bowel movements, rarely explosive, and far less violent than diarrhea associated with classic food poisoning (see later). Fever, bloating, fatigue, and abdominal pain are of minor to moderate severity. Nausea and vomiting are less frequently found than with viral gastroenteritis. Most TD is caused by bacteria, but a small percentage might be caused by viruses or parasites.

The affliction will resolve spontaneously in 2 to 5 days if untreated but might be hastened to a conclusion if an antibiotic is administered. The current recommendation is to treat adults with disabling (NOT with mild or moderate) TD with fever with azithromycin 1 g single dose or 500 mg by mouth once a day for 3 days (10 mg/kg [2.2 lb] of body weight in children once a day for 3 days). Treatment with ciprofloxacin 500 mg twice a day for 1 to 3 days or a single dose of 1 g, or norfloxacin 800 mg in a single dose is not recommended because of possible side effects and less efficacy. Trimethoprim–sulfamethoxazole is no longer recommended for TD because of bacterial resistance. In Nepal, ciprofloxacin is very poorly effective for TD, and azithromycin appears to be losing its effectiveness, all attributed to bacterial resistance.

Fortunately, another effective drug (so far) is rifaximin in a dose of 200 mg by mouth three times per day for 3 days. For known TD, the addition of loperamide (Imodium A-D) to the antibiotic regimen can be of significant benefit, with the precaution that it should be used only in the absence of high fever or bloody diarrhea. Alternatively, the diarrhea can be treated with bismuth subsalicylate (Pepto-Bismol); give two 262 mg tablets (or the liquid equivalent) every 30 minutes for eight doses, which may be repeated the second day. Kaolin and pectin given orally in combination might make the stools less runny, but do not shorten the duration of the diarrhea. Yogurt and lactobacillus preparations are not effective treatments. During the recovery period, it is fine to advance the diet fairly rapidly over a few days from clear liquids to bland foods to a normal diet.

To prevent TD, a person traveling to high-risk regions with questionable hygiene and municipal water disinfection standards (developing countries of Latin America, Africa, the Middle East, and Asia) can take rifaximin 200 mg, norfloxacin 400 mg, or ofloxacin 200 mg once a day during the journey. Another drug that can be used is doxycycline (Vibramycin) 100 mg twice a day. Rifamixin is preferred. Using antibiotics to prevent TD has been associated with creating a “carrier state” for antibiotic-resistant bacteria, so should only be done for special circumstances (see below).

Southern Europe (Spain, Greece, Italy, Turkey) and parts of the Caribbean pose a lesser risk. Using an antibiotic to prevent TD should be done under the guidance of a physician, who will explain the risks (allergic reactions, tendinitis, blood disorders, antibiotic-associated colitis, vaginal yeast infection, skin rashes, photosensitivity) versus the benefits (particularly for persons prone to infectious diarrhea or who would suffer unduly from an episode of severe diarrhea). Ingesting lactobacilli might improve certain aspects of digestion but does not prevent TD.

Alternatively, it has been recommended that you can drink 4 tablespoons (60 mL) of Pepto-Bismol (bismuth subsalicylate) four times a day; this necessitates carrying one 8 oz bottle for each day or taking tablets (two 262 mg tablets four times a day). However, this prophylaxis is not intended to substitute for dietary discretion. In addition, large doses of bismuth subsalicylate can be toxic, particularly to people who regularly use aspirin. Anyone with an aspirin allergy should not use bismuth subsalicylate. Side effects include blackened stools and a black tongue, nausea, constipation, and ringing in the ears.

People who would be advised to consider taking a drug to prevent infectious diarrhea include those with a significant underlying medical problem (such as acquired immunodeficiency syndrome [AIDS], inability to produce stomach acid, or inflammatory bowel disease) and those who are on an important assignment and with an itinerary schedule rigid enough that it would be catastrophic to the mission to be laid up with diarrhea.

Persistent diarrhea after travel to a developing country should provoke consideration of parasitic infection, such as with Giardia , Cryptosporidium , Entamoeba or Strongyloides , or bacterial infection, such as with E. coli , Shigella , Campylobacter , Salmonella or Vibrio . Other possibilities include viruses, worms, schistosomes, food intolerance, or inflammatory bowel disease.

Viral diarrhea

TD can also be caused by viruses. Viral gastroenteritis (commonly caused by rotaviruses [perhaps the most common cause of severe gastroenteritis in children less than 5 years of age and for which there are vaccines] or norovirus) includes diarrhea as a symptom. Norovirus (for which there is not yet a licensed vaccine) is the major problem with outbreaks of watery diarrhea on cruise ships, and increasingly common in long-term care facilities and schools. It has contaminated raw oysters. Viral gastroenteritis is often associated with nausea and vomiting, fever, stomach cramps, copious rectal gas, and a flu-like syndrome. The diarrhea is typically watery, frequent (up to 20 movements per day), often foul-smelling, discolored (green to greenish brown), and without significant mucus or blood. Generally, the victim will have cyclic waves of lower abdominal cramps, relieved by bowel movements. The incubation period between viral contact (fecal-oral transmission; usually hand-to-mouth) and illness is 1 to 3 days. Usually viral gastroenteritis is self-limited with recovery in 2 to 5 days. If viral gastroenteritis is suspected, limit contact with the ill persons and for 1 to 2 days after illness, and clean contaminated surfaces with a 1:50 to 1:10 dilution of household chlorine bleach in water solution, or other bleach-based disinfectant. An infected person should not prepare food and optimally should avoid contact with other persons for at least 2 days after symptoms have ceased. Because there are many types of norovirus, a person can become infected a number of times. The most important aspect of personal protection is rigorous hand washing with soap and warm water for at least 20 seconds. Clothing of an infected person should be washed with hot water and detergent and then run through a hot dryer cycle.

It is critical to keep the victim from becoming dehydrated. What comes out below should be replaced from above. Therapy requires continual oral hydration with clear liquids such as apple juice or broth. If they are available, drink electrolyte-containing beverages.

The cramps can be controlled with loperamide (Imodium A-D), which will also help limit the diarrhea. It should be noted, however, that these drugs will slow down the activity of the bowel and allow any toxins that are in the gut to remain in contact with the bowel wall. With certain bacterial and viral infections, these drugs might prolong the carrier state and actually increase the severity and duration of the disease. Therefore, it is prudent to avoid the use of loperamide unless the intake of fluids cannot keep pace with the diarrhea and severe dehydration is becoming a real concern. Never give an antimotility agent to an infant. Loperamide can be used in children aged 2 years and older if the diarrhea is watery and nonbloody, there is no associated fever, and diarrhea is leading to debilitating dehydration. Give a child a 0.2 mg/kg (2.2 lb) of body weight dose every 6 hours. The liquid preparation contains 1 mg/teaspoon (5 mL).

Cryptosporidiosis

Cryptosporidiosis is caused by Cryptosporidium parvum or hominis , which are commonly found in surface water in the United States. It is also commonly associated with non-U.S. travel. Infection is caused by ingestion of the oocysts and manifested by watery diarrhea, abdominal cramps, nausea and vomiting, fatigue, and low-grade fever. Persons who are immunosuppressed might suffer more severe symptoms. The cysts are 2 microns in diameter. Symptoms begin 2 to 14 days after ingestion, and might last for up to 2 weeks, with a carrier state of up to 2 months. Treatment is nitazoxanide 500 mg by mouth twice a day for 3 days in adults, and 100 mg twice a day in children up to age 12. Another effective treatment is azithromycin 500 mg by mouth once a day for 5 days in adults or paromomycin 500 mg three times a day for 7 days. Proper hand washing is essential to prevention, because alcohol-based (gel) hand sanitizers do not kill Cryptosporidium . If someone is felt to be suffering from diarrhea that might be cryptosporidiosis, it is advised to not swim (e.g., not contaminate the water) for at least 2 weeks after all symptoms resolve.

Food poisoning

Food poisoning is caused by toxins that are produced by a number of bacteria, with the most common being Staphylococcus . Improper preservation (generally, lack of refrigeration) of food allows bacterial proliferation, which is not corrected by cooking. Typically, the symptoms occur 2 to 6 hours after eating and consist of severe abdominal cramps with nausea and vomiting. Diarrhea might be delayed by an hour or two, or might occur simultaneously with the nausea and vomiting. The diarrhea is often explosive. As with viral gastroenteritis, the bowel movements might be foul-smelling and blood-tinged. The disease is self-limited, and generally subsides after 6 to 12 hours. Treatment consists of rehydration with clear liquids. Antimotility drugs, such as loperamide (Imodium A-D) or diphenoxylate (Lomotil), might prolong the disorder, and should not be used unless the victim cannot replenish fluid losses.

Escherichia coli O157:H7

E. coli O157:H7 is a bacterium that has been transmitted by as few as 10 bacteria in raw or undercooked hamburger meat, fruit E. coli O157:H7 juices, and other food with fecal contamination. It can be spread person to person, and has also been transmitted by petting animals, contacting animal manure, and swimming in recreational pool water. As has been noted previously, in the presence of someone with any cause of diarrhea, excellent handwashing technique should be observed. If a person is ill with a diarrheal illness, they should not prepare food for others or share common bodies of swimming or bathing water. Try to not swallow lake or swimming pool water.

After ingesting the bacteria, an infection can occur after an incubation period of 1 to 10 days, with 3 days being the average delay between exposure and illness. It causes a syndrome of fever or no fever, abdominal pain, vomiting, and nonbloody diarrhea, followed in a few days by bloody diarrhea, dehydration, weakness, anemia, and kidney failure. There is not yet an effective treatment with antibiotics. In fact, therapy with some antibiotics might contribute to more severe illness (see later). Prevention means strict handwashing before eating and cooking ground beef until it is no longer pink (160°F [71°C]). Do not mix raw and cooked foods, particularly meat. After you cook meat, do not serve it on the unwashed dish that carried the raw food. Since raw meat, especially beef, can be a problem, be certain to wash hands, cooking utensils, cutting boards, dishes, and counters after they have been in contact with raw meat. Milk and fruit juices prepared from crushing processes require pasteurization. Understand that in the absence of pasteurization, which is a heating process, no product can be guaranteed to not be contaminated with the bacteria normally killed in the pasteurization process. Many of us like to drink fresh fruit juice. When we do so, we take a risk, usually quite minor, that it might be contaminated.

For treatment of known or highly suspected E. coli O157:H7 infection, antibiotics are not recommended. This is because in some cases, antibiotics might worsen the affliction. The precise reason this happens is not known, but one suggestion is that by causing rapid death of large numbers of bacteria, large amounts of the Shiga toxin (also known as verocytotoxin) are released, which causes the medical problems. Antidiarrheal agents, such as loperamide (Imodium), are also not recommended, because they are thought to possibly keep the bacteria in contact with the bowel for longer periods of time. Most patients recover without antibiotics in approximately a week. Severely dehydrated individuals might require intravenous fluids. Children infected with E. coli O157:H7 are at higher risk than are adults for developing hemolytic-uremic syndrome, in which they might suffer anemia and kidney failure.

The difficulty with the recommendation to withhold antibiotics is that it is very difficult to make a precise field diagnosis of any particular cause of diarrhea. So, antibiotics are often given until confirmation of the infectious agent is reported by a laboratory.

Giardia lamblia

G. lamblia is a flagellate protozoan (one-celled organism) that has become a worldwide problem, particularly in wilderness settings in the western United States, Nepal, and the Soviet Union. It is transmitted as cysts in the feces of many animals, which include humans, elk, beavers, deer, cows, dogs, and sheep. Dormant Giardia cysts enter water, from where they are ingested by humans. Cysts can live for up to 3 months in cold water.

If more than 10 to 25 cysts are swallowed, the organisms establish residence in the duodenum and jejunum (first parts of the small bowel), and after an incubation period of 7 to 20 days emerge in another form (trophozoite) to cause stomach cramps, flatulence, a swollen lower abdomen, often explosive and foul-smelling watery (“floating”) diarrhea, “rotten” (sulfurous) belching, and nausea. Fever and vomiting are unusual except in the first few days of illness. Foul flatus and abdominal cramping are common. Because of the delay in onset after ingestion of the cysts, many a backpacker develops “backpacker’s diarrhea” or “beaver fever” after they return to civilization and do not recognize the causal link to the recent journey. If the diarrhea becomes chronic, the victim can lose appetite and weight and become weak. Diagnosis is made by a physician who recognizes trophozoites or microscopic cysts in the stool of the victim, takes a sample of mucus from the duodenum, or is confident with a clinical diagnosis.

Untreated, the illness usually resolves after about 6 weeks. However, the diarrhea might go on for months. Therapy for Giardia infestation is administration of metronidazole (Flagyl) 250 to 500 mg three times a day for 7 to 10 days; the pediatric dose is 5 mg/kg (2.2 lb) of body weight to a maximum of 250 mg per dose administered three times per day. Another excellent drug is tinidazole (Tindamax, Tiniba, Fasigyn), which is taken in a 2-g dose for 1 or 2 days; the pediatric dose is 50 mg/kg (2.2 lb) of body weight in a single dose. Another prescription therapy is quinacrine hydrochloride (Atabrine) 100 mg twice a day for 7 days; the pediatric dose is 7 mg/kg (2.2 lb) of body weight per day in three divided doses for 7 days. Unfortunately, quinacrine has side effects (which occur in 1 to 4 out of every 1000 people) that include making the person psychotic (lose touch with reality) for up to a few weeks. A good therapy for children is furazolidone (Furoxone) 6 mg/kg of body weight in four divided doses for 7 days. There have been mixed reports of success with albendazole given in a dose of 400 mg/day for 3 to 5 days. Particularly when an expedition will not reach civilization for 3 to 4 weeks, there is no reason to withhold treatment awaiting a definitive diagnosis. If the field diagnosis is correct, in most cases drug therapy will cause dramatic relief from symptoms within 3 days. There is no prophylactic drug that is recommended to prevent infestation.

Other infectious diarrheas

Diarrhea can be caused by a number of parasites and other infectious agents, which include Campylobacter, Shigella, Salmonella, Yersinia, Vibrio , Cryptosporidium, and Entamoeba histolytica (and other protozoa that cause amebiasis). Campylobacter jejuni are the bacteria that most commonly cause diarrhea in the United States, often noted after eating contaminated poultry. Although up to a quarter of persons who are infected are without symptoms, those who become ill frequently exhibit nausea, severe diarrhea, and abdominal pain. Campylobacter upsaliensis causes bloody diarrhea in dogs. Campylobacter infection is treated with azithromycin 500 mg by mouth once a day for 3 days. The pediatric dose is 10 mg/kg (2.2 lb) of body weight up to 500 mg by mouth once a day for 3 days. Campylobacter infection can also be treated with erythromycin 500 mg four times a day for 5 days.

Amebic dysentery is caused by E. histolytica , the symptoms of which are the (usually) gradual onset of diarrhea (watery or bloody, frequent, copious, and sometimes with fever) that does not respond to antibiotics, characterized by severe lower abdominal pain and a swollen abdomen. In an endemic area, presumptive field treatment is with metronidazole 750 mg by mouth three times a day for 10 days or tinidazole 600 mg by mouth for 5 days. This is accompanied by eradication of the cyst forms remaining in the bowel wall with a drug such as paromomycin (25 to 35 mg/kg body weight in three divided doses for 10 days) or diloxanide furoate (500 mg by mouth three times a day for 7 days). Cryptosporidium infection is treated with nitazoxanide (Alinia) in a dose of 500 mg by mouth twice a day for 3 days. Algal diarrhea (a cause of diarrhea more commonly noted in Nepal and Peru) is caused by Cyclospora cayetanensis and is treated with trimethoprim–sulfamethoxazole one double-strength tablet twice a day for 7 days. Cystoisospora belli infection is treated with trimethoprim–sulfamethoxazole one double-strength tablet four times a day for 10 days.

Diarrhea-causing pathogens cause a constellation of fever, chills, nausea, vomiting, diarrhea (with or without mucus and blood), weakness, and abdominal pain. Because the clinical picture can be similar with infection from any of these organisms, the differentiation between them frequently relies on examination of the stool under the microscope and/or culture of the stool to identify the specific pathogen. For the sake of the brief expedition, the treatment is the same: rehydration with copious amounts of balanced electrolyte solutions, and antimotility agents only when essential to prevent severe dehydration. If the victim suffers from high fever with shaking chills, has persistent bloody or mucus-laden bowel movements, or is debilitated by dehydration, they should seek the care of a physician. Meanwhile, administration of azithromycin 1 g once a day or ciprofloxacin 500 mg two times a day (or 750 mg once a day) for 3 days will treat E. coli and Shigella . Infection with Salmonella can be treated with levofloxacin 500 mg (or another fluoroquinolone antibiotic) once a day for 7 to 10 days. The pediatric dose for either ciprofloxacin or azithromycin for this purpose is 10 mg/kg (2.2 lb) of body weight up to the adult dose, given twice a day by mouth. (Ampicillin or trimethoprim-sulfamethoxazole are alternatives.) As soon as the victim of persistent diarrhea returns to civilization, they should visit a physician for a thorough evaluation. If the ova or parasitic forms of amoebae are seen during microscopic examination of stool, other drugs, such as tinidazole, metronidazole, diloxanide furoate, paromomycin, or diiodohydroxyquin, can be prescribed. If the ova or parasitic forms of worms are seen, drugs such as ivermectin, mebendazole or pyrantel pamoate can be prescribed. Treating the “chronic carrier” condition in which a person harbors typhoidal salmonella involves 4 to 6 weeks of antibiotic treatment.