What is the most likely diagnosis?A 40-year-old man presents to the clinic complaining of having 10 episodes of watery, nonbloody diarrhea that started last night. He vomited twice last night but has been able to tolerate liquids today. He has had intermittent abdominal cramps as well. He reports having muscle aches, weakness, headache, and low-grade temperature. He is here with his daughter, who started with the same symptoms this morning. On questioning, he states that he has no significant medical history, no surgeries, and does not take any medications. He does not smoke cigarettes, drink alcohol, use any illicit drugs, and has never had a blood transfusion. He and his family returned to the United States yesterday, following a week-long vacation in Mexico.
On examination, he is not in acute distress. His blood pressure is 110/60 mm Hg, his pulse is 98 beats/min, his respiratory rate is 16 breaths/min, and his temperature is 99.1°F (37.2°C). His mucous membranes are dry. His bowel sounds are hyperactive and his abdomen is mildly tender throughout, but there is no rebound tenderness and no guarding. A rectal examination is normal and his stool is guaiac negative. The remainder of his examination is unremarkable.
What is the most likely diagnosis?
What is your next step?
What are potential complications?
Summary: A 40-year-old man who recently returned from Mexico with profuse, acute, nonbloody diarrhea and dry mucous membranes on examination, which are consistent with developing dehydration. An ill family member with identical symptoms suggests an infectious cause of this acute illness.
• Most likely diagnosis: Acute gastroenteritis
• Next step: Order stool for fecal leukocytes
• Potential complication: Dehydration and electrolyte abnormalities
1. To clearly understand when and how to do a workup for acute diarrhea, considering the most probable etiologies of diarrhea such as virus, Escherichia coli, Shigella, Salmonella, Giardia, and amebiasis.
2. To understand the role of fecal leukocytes and stool occult blood in the evaluation of acute diarrhea.
3. To understand that volume replacement and correction of electrolyte abnormalities are a key component in the treatment and prevention of diarrhea complications.
This 40-year-old man developed severe diarrhea, nausea, and vomiting. His most immediate problem is volume depletion, as evidenced by his dry mucous membranes. The priority is to replace the lost intravascular volume, usually with intravenous normal saline. Electrolytes and renal function should be evaluated and abnormalities corrected. While correcting and/or preventing further dehydration, you need to determine the etiology of the diarrhea. Up to 90% of acute diarrhea is infectious in etiology. He does not have any history compatible with chronic diarrhea, causes of which include Crohn disease, ulcerative colitis, gluten intolerance, irritable bowel syndrome, and parasites. He had been in Mexico recently, which predisposes him to different pathogens: E coli, Campylobacter, Shigella, Salmonella, and Giardia. He does not have bloody stools. The presence of blood in the stool would suggest an invasive bacterial infection, such as hemorrhagic or enteroinvasive E coli species, Yersinia species, Shigella, and Entamoeba histolytica.
Examination of the stool for leukocytes is a simple, inexpensive test that helps to differentiate between the types of infectious diarrhea. If leukocytes are present in the stool, the suspicion is higher for Salmonella, Shigella, Yersinia, enterohemorrhagic and enteroinvasive E coli, Clostridium difficile, Campylobacter, and E histolytica. In general, ova and parasite evaluation is unhelpful, unless the history strongly points toward a parasitic source or the diarrhea is prolonged.
The majority of the diarrheas are viral, self-limited, and do not need further evaluation. In this particular patient, because of his recent travel to Mexico, traveler’s diarrhea should be strongly considered and treated with the appropriate antibiotic.
ACUTE DIARRHEA: Diarrhea present for less than 2-week duration
CHRONIC DIARRHEA: Diarrhea present for longer than 4-week duration
DIARRHEA: Passage of abnormally liquid or poorly formed stool in increased frequency (three or more times a day)
SUBACUTE DIARRHEA: Diarrhea present for 2- to 4-week duration
Approximately 90% of acute diarrhea is caused by infectious etiologies, with the remainder caused by medications, ischemia, and toxins. Infectious etiologies often depend on the patient population. Travelers to Mexico will frequently contract enterotoxigenic E coli as a causative agent. Traveler’s diarrhea is a common entity and can be induced by a variety of bacteria, viruses, and parasites (Table 10–1). Campers are often affected by Giardia.
Table 10–1 • COMMON ETIOLOGIES OF TRAVELER’S DIARRHEA
Consumption of foods is also frequently a culprit. Salmonella or Shigella can be found in undercooked chicken, enterohemorrhagic E coli from undercooked hamburger, and Staphylococcus aureus or Salmonella from mayonnaise. Raw seafood may harbor Vibrio, Salmonella, or hepatitis A. Sometimes the timing of the diarrhea following food ingestion is helpful. For example, illness within 6 hours of eating a salad containing mayonnaise suggests S aureus, within 8 to 12 hours suggests Clostridium perfringens, and within 12 to 14 hours suggests E coli.
Daycare settings are particularly common for Shigella, Giardia, and rotavirus to be transmitted. Patients in nursing homes, or who were recently in the hospital, may develop C difficile colitis from antibiotic use.
Most patients with acute diarrhea have self-limited processes and do not require much workup. Exceptions to this rule include profuse diarrhea, dehydration, fever exceeding 100.4°F (38.0°C), bloody diarrhea, severe abdominal pain, duration of the diarrhea for more than 48 hours, and children, elderly patients, and immunocompromised patients. Traveler’s diarrhea is characterized by greater than three loose stools in a 24-hour period accompanied by abdominal cramping, nausea, vomiting, fever, or tenesmus. Most cases occur within the first 2 weeks of travel.
Past and recent medical history should include exposures to medications and foods, travel history, and coworkers, classmates, or family members with similar symptoms. A history of a viral illness may provide a clue to the etiology. The initial evaluation should determine if the patient can tolerate oral intake. The patient who is both vomiting and having diarrhea is more prone to dehydration and more likely to need hospital admission for IV hydration.
The physical examination should focus on the vital signs, clinical impression of the volume status, and abdominal examination. Volume status is determined by observing whether the mucous membranes are moist or dry, the skin has good turgor, and the capillary refill is normal or delayed. The principal laboratory test is the stool for microscopic and microbiologic examination; usually it is sent for culture, but these results generally require several days to obtain and are not useful in the acute setting. Ova and parasite evaluation is generally unhelpful, except in selected circumstances of very high suspicion. Stool for C difficile toxin may yield the etiology in patients who develop symptoms after antibiotic use. Although classically associated with clindamycin, any antibiotic can cause pseudomembranous colitis. A complete blood count, electrolytes, and renal function tests are sometimes indicated.
Most cases of diarrhea resolve spontaneously in a few days without treatment. Replacement of fluids and electrolytes is the first step in treating the consequences of acute diarrhea. For mildly dehydrated individuals who can tolerate oral fluids, solutions such as the World Health Organization oral rehydration solution or commercially available drinks such as Pedialyte or Gatorade, often are all that is needed. Those with more serious volume deficits, elderly patients, and infants generally require hospitalization and intravenous hydration. If a parasitic infection is the cause of the diarrhea, prescription antibiotics may ease the symptoms. Antibiotics sometimes, but not always, help ease symptoms of bacterial diarrhea. However, antibiotics will not help viral diarrhea, which is the most common kind of infectious diarrhea. Over-the-counter antimotility or antisecretory medications may help to slow down the frequency of the stools, but they do not speed the recovery. Certain infections may be made worse by over-the-counter medications because they prevent your body from getting rid of the organism that is causing the diarrhea. Probiotics, supplements that contain live organisms such as Lactobacillus sp or Saccharomyces Boulardii, may reduce the incidence of antibiotic-related diarrhea and the duration/severity of all-cause infectious diarrhea (Level A recommendation).
Hand washing is a simple and effective way to prevent the spread of viral diarrhea. Adults, children, and clinic and hospital personnel should be encouraged to wash their hands. Because viral diarrhea spreads easily, children with diarrhea should not attend school or child care until their illness has resolved.
To prevent diarrhea caused by contaminated food, use dairy products that have been pasteurized. Serve food immediately or refrigerate it after it has been cooked. Do not leave food out at room temperature because it promotes the growth of bacteria.
Travelers to locations, such as developing countries, where there is poor sanitation and frequent contamination of food and water, need to be cautious to reduce their risk of developing diarrhea. They should be advised to eat hot and well-cooked foods, and to drink bottled water, soda, wine, or beer served in its original container. Avoid drinks served over ice. Beverages from boiled water, such as coffee and tea, are usually safe. Recommend the use of bottled water even for teeth brushing. Also recommend avoiding raw fruits and vegetables unless they are peeled by the consumer immediately before being eaten. Patients should avoid tap water and ice cubes. In all, these recommendations may reduce but not completely eliminate one’s risk of developing traveler’s diarrhea.
The best method for preventing traveler’s diarrhea (TD) is to avoid contaminated food and water. Antibiotic prophylaxis is not indicated unless the patient is at increased risk for complications from diarrhea or dehydration, such as underlying inflammatory bowel disease, renal disease, or an immunocompromised state. Fluoroquinolones are typically used for prophylaxis.
When antibiotics are indicated, therapy with a quinolone antibiotic should be started as soon as possible after the diarrhea begins. Most commonly, ciprofloxacin (500 mg twice daily) is given for 1 or 3 days. Quinolones cannot be used in children or pregnant women. Quinolones will resolve the diarrheal symptoms in the majority of patients within 1 day. Azithromycin, given as a single 1000-mg dose in adults or 10 mg/kg daily for 3 days in children, is another effective drug for the treatment of TD. Azithromycin also can be used in pregnant women with traveler’s diarrhea. Rifaximin given as 200 mg three times a day for 3 days can be used in TD caused by noninvasive strains of E coli. However, Rifaximin is not effective against infections associated with fever or blood in the stool.
Trimethoprim-sulfamethoxazole and ampicillin were popular drugs used in the past to treat TD, but increased resistance limits their use at this time. Bismuth subsalicylate is not recommended because, to be effective, it needs to be taken in large amounts (2 fl oz four times daily for up to 3 weeks) that can cause salicylate toxicity especially in persons taking anticoagulants or other salicylates. Bismuth subsalicy-late should also be avoided in persons allergic to aspirin, pregnant women, or those taking methotrexate, probenecid, or doxycycline for malaria prophylaxis. The evidence is insufficient regarding the efficacy of probiotics as prophylaxis for TD.
10.1 Several friends develop vomiting and diarrhea 6 hours after eating food at a private party. Which of the following is the most likely etiology of the symptoms?
A. Rotavirus
B. Giardia
C. E coli
D. S aureus
E. Cryptosporidium
F. Vibrio
G. Excessive alcohol
10.2 A 40-year-old man travels to Mexico and develops diarrhea 1 day after coming back to the United States. Which of the following is the most likely etiology of the symptoms?
A. Rotavirus
B. Giardia
C. E coli
D. S aureus
E. Cryptosporidium
F. Vibrio
10.3 A young woman eats raw seafood and 2 days later develops fever, abdominal cramping, and watery diarrhea. Which of the following is the most likely etiology of the symptoms?
A. Rotavirus
B. Giardia
C. E coli
D. S aureus
E. Cryptosporidium
F. Vibrio
10.4 During the winter, a young daycare worker develops watery diarrhea. Which of the following is the most likely etiology of the symptoms?
A. Rotavirus
B. Giardia
C. E coli
D. S aureus
E. Cryptosporidium
F. Vibrio
10.5 A 45-year-old man presents with 3 days of watery diarrhea and abdominal cramping. He has no sick contacts and has not traveled recently. He is not currently taking any medications, but he was prescribed amoxicillin 2 weeks ago for a sinus infection. Which of the following tests is most likely to identify the cause of his diarrhea?
A. Stool guaiac
B. Evaluation of stool for fecal leukocytes
C. Evaluation of stool for ova and parasites
D. C difficile toxin immunoassay
10.6 In the patient described in question 10.5, which of the following is the treatment of choice for his diarrhea?
A. Ciprofloxacin
B. Azithromycin
C. Metronidazole
D. Loperamide
10.1 D. S aureus toxin usually causes vomiting and diarrhea within a few hours of food ingestion.
10.2 C. E coli is the most common etiology for traveler’s diarrhea.
10.3 F. Vibrio is a common cause of diarrhea among people who eat raw seafood.
10.4 A. Rotavirus is a common etiology for watery diarrhea, especially in the winter.
10.5 D. Although any antibiotic can cause C difficile colitis, clindamycin, cephalosporins, and penicillins are the most commonly implicated.
10.6 C. Metronidazole or oral vancomycin can be used to treat C difficile. Ciprofloxacin and azithromycin can be used for treatment of traveler’s diarrhea. Loperamide can decrease the frequency of bowel movements but is contraindicated in any patient with suspected C difficile colitis.
Most acute diarrheas are self-limited.
Be cautious when assessing diarrhea in a child, elderly patient, or immunosuppressed host.
Dehydration, bloody diarrhea, high fever, and diarrhea that do not respond to therapy after 48 hours are warning signs of possible complicated diarrhea.
In general, acute, uncomplicated diarrhea can be treated with oral electrolyte and fluid replacement.
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