A 7-year-old boy is brought to the emergency department due to bloody diarrhea. The patient was previously in good health. He began having mild watery stools 18 days ago that have gradually become more frequent. For the past 3 days, the stools have been grossly bloody. The family has just returned from a 4-week trip to Pakistan to visit extended family. Temperature is 36.8 C (98.2 F); other vital signs are normal. Physical examination shows mild left lower quadrant tenderness and active bowel sounds. There is no rebound tenderness. Stool samples are sent for microbiologic studies. Which of the following is the most likely cause of this patient's symptoms?

Question

A 7-year-old boy is brought to the emergency department due to bloody diarrhea.  The patient was previously in good health.  He began having mild watery stools 18 days ago that have gradually become more frequent.  For the past 3 days, the stools have been grossly bloody.  The family has just returned from a 4-week trip to Pakistan to visit extended family.  Temperature is 36.8 C (98.2 F); other vital signs are normal.  Physical examination shows mild left lower quadrant tenderness and active bowel sounds.  There is no rebound tenderness.  Stool samples are sent for microbiologic studies.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d5fe_4386_bc81_8b533c1b6676_MD0003_00 Evaluation of travel-associated diarrhea is based on duration of symptoms and presence or absence of blood in the stool. Diarrhea lasting >2 weeks is typically parasitic rather than bacterial or viral. This patient with persistent bloody diarrhea after visiting a developing country most likely has amebiasis due to Entamoeba histolytica infection. Common clinical findings of amebiasis include prolonged diarrhea (median of 2-3 weeks) that progresses to colitis (eg, abdominal tenderness, bloody diarrhea). Although amebic liver disease classically causes right upper quadrant pain, colitis can cause tenderness in different abdominal quadrants. Fever is uncommon. Diagnosis is made by repeated examination of the stool for E histolytica antigen, either by enzyme immunoassay or by molecular tests (eg, PCR testing). Treatment of amebic colitis is metronidazole (to eliminate trophozoites in tissue) and a luminal agent such as paromomycin. (Choice A) Cryptosporidium infection causes watery diarrhea that is short-lived in healthy hosts. Immunocompromised hosts may have prolonged (>2 weeks) diarrhea, malabsorption, and weight loss; colitis is rarely seen. (Choice C) Escherichia coli is the leading cause of traveler's diarrhea, which presents as watery diarrhea and crampy abdominal pain 1-3 days after ingestion of contaminated water or food. Infections are self-limited and typically resolve in <7 days with supportive therapy. (Choice D) Giardia intestinalis is among the most frequent causes of prolonged diarrhea in returning travelers in addition to E histolytica. However, giardiasis causes prolonged watery diarrhea and fat malabsorption. Greasy, smelly stools and bloating are characteristic, not bloody stools. (Choice E) Cholera causes acute, profuse watery diarrhea. Mild cases are indistinguishable from other causes of traveler's diarrhea (eg, E coli). However, profound fluid losses, "rice-water" stools, and vomiting of severe cholera are distinctive. This child's prolonged diarrhea and bloody stools are inconsistent with cholera infection. Educational objective: Travel-associated diarrhea lasting >2 weeks is most commonly parasitic, and Entamoeba histolytica infection should be suspected in returning travelers with prolonged bloody diarrhea. References: A review of the global burden, new diagnostics, and current therapeutics for amebiasis. (http://www.ncbi.nlm.nih.gov/pubmed/30046644) Illness in the returned international traveler. (http://www.ncbi.nlm.nih.gov/pubmed/26900121)

A 7-Year-Old Boy Is Brought to the Emergency Department Due