A 23-year-old man comes to the emergency department with a 5-day history of diarrhea and abdominal pain. The diarrhea occurs 5-6 times a day; it was initially watery but since yesterday has become bloody. He describes the abdominal pain as colicky and severe, with associated nausea and decreased appetite but no vomiting. The patient's past medical history is insignificant, with no prior episodes of similar symptoms and no recent hospitalizations or illnesses. He is not sexually active and does not use illicit drugs. The patient lives in Boston. He has no history of recent travel and no close contacts with similar symptoms. The patient's father had colon cancer at age 50, and his uncle died of liver cirrhosis. His temperature is 36.6 C (98.0 F), blood pressure is 123/82 mm Hg, and pulse is 102/min. He has prominent periumbilical and right lower quadrant tenderness but no guarding or rebound. Rectal examination shows brownish stool mixed with blood. Which of the following is the most likely etiology in this patient?

Question

A 23-year-old man comes to the emergency department with a 5-day history of diarrhea and abdominal pain.  The diarrhea occurs 5-6 times a day; it was initially watery but since yesterday has become bloody.  He describes the abdominal pain as colicky and severe, with associated nausea and decreased appetite but no vomiting.  The patient's past medical history is insignificant, with no prior episodes of similar symptoms and no recent hospitalizations or illnesses.  He is not sexually active and does not use illicit drugs.  The patient lives in Boston.  He has no history of recent travel and no close contacts with similar symptoms.  The patient's father had colon cancer at age 50, and his uncle died of liver cirrhosis.  His temperature is 36.6 C (98.0 F), blood pressure is 123/82 mm Hg, and pulse is 102/min.  He has prominent periumbilical and right lower quadrant tenderness but no guarding or rebound.  Rectal examination shows brownish stool mixed with blood.  Which of the following is the most likely etiology in this patient?

Quizplus · Accepted Answer

11ec25c8_d43d_80e7_bc81_a7de68d260d1_MD0003_00 This patient has acute onset of bloody diarrhea associated with abdominal pain. In the absence of travel history, the differential diagnosis for this acute illness is relatively limited. Bloody diarrhea is most often caused by bacterial pathogens, specifically Escherichia coli, Shigella, and Campylobacter; other organisms that often cause watery stools can occasionally cause bloody stools (eg, Salmonella). The most common cause of bloody diarrhea in the absence of fever is E coli. The enterohemorrhagic E coli (EHEC) strain produces Shiga toxin, which causes an inflammatory diarrhea syndrome with bloody stools and abdominal pain. EHEC infection is most frequently associated with consumption of contaminated beef products, although there have been documented outbreaks associated with other foods such as fruits, leafy vegetables, and milk products. Isolated cases without a clear source are also common. The diagnosis can be confirmed with assay for Shiga toxin in stool. Stool culture can also identify toxin-producing strains. Treatment is generally supportive; antibiotics are not helpful and may increase the risk of hemolytic uremic syndrome. (Choice A) Clostridium difficile-associated diarrhea presents as frequent, foul-smelling loose stools associated with prior antibiotic use or exposure to healthcare settings. Infection in a patient without these risk factors is uncommon and bloody diarrhea is atypical. (Choice B) Clostridium perfringens is a common cause of a toxin-mediated, foodborne illness leading to nonbloody diarrhea and abdominal pain. (Choice D) Rotavirus is a frequent cause of acute gastroenteritis with nonbloody diarrhea and vomiting. It typically occurs in outbreaks among children, although adults may be affected as well. (Choice E) Staphylococcus aureus is a common cause of foodborne illness and often occurs in small outbreaks. Symptoms usually begin within a few hours of ingesting preformed toxin from contaminated food. Most patients experience vomiting and abdominal pain. Fever and diarrhea may also be seen, but bloody stools are not typical. Educational objective: Enterohemorrhagic Escherichia coli (EHEC) is a food-borne pathogen that causes acute watery to bloody diarrhea. Diagnosis can be confirmed with a stool assay for Shiga toxin. If EHEC is suspected, empiric antibiotic therapy should be avoided as it may increase the risk of hemolytic uremic syndrome. References: Escherichia coli diarrhea in the United States (http://www.ncbi.nlm.nih.gov/pubmed/9092315) Diagnosis and management of foodborne illnesses: a primer for physicians. (http://www.ncbi.nlm.nih.gov/pubmed/11214980)

A 23-Year-Old Man Comes to the Emergency Department with a 5-Day