A 36-year-old man comes to the emergency department due to a 3-day history of abdominal pain and diarrhea. The patient returned yesterday from a 1-week vacation in Belize, where he often ate street food. At the end of his trip, he developed diarrhea with about 10 watery, nonbloody stools a day. Over the past 24 hours, the patient's urine output has decreased. He has felt nauseated but has been able to tolerate fluids without vomiting. The patient has taken no recent medications. Temperature is 37.5 C (99.5 F), blood pressure is 105/62 mm Hg, and pulse is 112/min. On examination, the mucous membranes and lips appear dry, and capillary refill is 3 seconds. The abdomen is mildly distended and tender to deep palpation periumbilically; bowel sounds are hyperactive. Stool occult blood is negative. Laboratory results are as follows: Which of the following is the most likely etiology of this patient's illness?

Question

A 36-year-old man comes to the emergency department due to a 3-day history of abdominal pain and diarrhea.  The patient returned yesterday from a 1-week vacation in Belize, where he often ate street food.  At the end of his trip, he developed diarrhea with about 10 watery, nonbloody stools a day.  Over the past 24 hours, the patient's urine output has decreased.  He has felt nauseated but has been able to tolerate fluids without vomiting.  The patient has taken no recent medications.  Temperature is 37.5 C (99.5 F), blood pressure is 105/62 mm Hg, and pulse is 112/min.  On examination, the mucous membranes and lips appear dry, and capillary refill is 3 seconds.  The abdomen is mildly distended and tender to deep palpation periumbilically; bowel sounds are hyperactive.  Stool occult blood is negative.  Laboratory results are as follows: Which of the following is the most likely etiology of this patient's illness?

Quizplus · Accepted Answer

11ec25c8_d278_c6a0_bc81_698109ebd8f1_MD0003_00 This patient who recently vacationed in Belize has travelers' diarrhea, or diarrhea occurring during or within 10 days after travel to a resource-limited country. The most common cause of travelers' diarrhea with watery stools is enterotoxigenic Escherichia coli (ETEC), which is transmitted fecal-orally from contaminated food or water. Visitors who buy food from street vendors are particularly susceptible due to a high risk of poor sanitation and hygiene in food-handling. In contrast to pathogens with preformed toxin (eg, Staphylococcus aureus), which cause symptoms within hours, ETEC produces an enterotoxin after ingestion with symptoms usually starting within 1-3 days of transmission. Patients have an acute onset of watery diarrhea and abdominal pain (eg, tenderness to deep palpation, mild distension). Low-grade fever, nausea, and/or vomiting may occur. Bloody stools are atypical and suggest a different pathogen (eg, Shigella, Campylobacter). Symptoms of ETEC gastroenteritis usually self-resolve within 5 days. However, severe diarrhea can lead to dehydration (eg, dry mucous membranes, prolonged capillary refill, tachycardia), which can cause prerenal azotemia (ie, blood urea nitrogen/creatinine ratio >20:1, decreased urinary output) and hypernatremia (as seen here). (Choice B) Giardia can also cause watery diarrhea after travel to a resource-limited area. However, symptom onset is >1 week after exposure because the pathogenesis involves replication and colonization within the small bowel, resulting in villous shortening and malabsorption. This patient, who developed symptoms within days of travel, was more likely infected with an enterotoxin-producing organism. (Choice C) Rotavirus usually presents with severe, watery diarrhea in unimmunized children age <2; mild, self-limited illness can occur in adolescents/adults. This patient's progressive symptoms and dehydration make this diagnosis unlikely. In addition, his exposure to street food is most closely associated with ETEC. (Choice D) Salmonella serovar Typhi, typically acquired in resource-limited countries, initially causes high fever for a week followed by abdominal pain with or without diarrhea. This patient's diarrhea at the onset of symptoms and lack of fever makes S Typhi unlikely. (Choice E) Most patients with Shiga toxin-producing E coli have self-limited bloody diarrhea. A minority develop hemolytic uremic syndrome (HUS) after 1-2 weeks, which is inconsistent with this patient's timeline. In addition, HUS typically intrinsic acute kidney injury (eg, blood urea nitrogen/creatinine ratio <20:1) and is associated with anemia and thrombocytopenia. Educational objective: Travelers' diarrhea presents after travel to a resource-limited area with poor sanitation. The most common cause is enterotoxigenic Escherichia coli, which is a generally self-limited illness that causes the acute onset of watery diarrhea and abdominal pain. References: Traveler's diarrhea: a clinical review. (http://www.ncbi.nlm.nih.gov/pubmed/25562268) Traveler's diarrhea. (http://www.ncbi.nlm.nih.gov/pubmed/26900116)

A 36-Year-Old Man Comes to the Emergency Department Due to a 3-Day