A 34-year-old man comes to the office with a 4-week history of diarrhea. He has no blood in the stools. The patient recently returned from a trip to South America, where he developed foul-smelling stools, abdominal cramps, and bloating. A 3-day course of ciprofloxacin did not relieve his symptoms. He has no previous medical problems and has never had similar symptoms. The patient takes no other medication and does not use tobacco, alcohol, or illicit drugs. Temperature is 36.8 C (98.2 F), blood pressure is 126/80 mm Hg, and pulse is 86/min. Examination shows a soft, nontender abdomen with increased bowel sounds. Which of the following is the most appropriate next step in management?

Question

A 34-year-old man comes to the office with a 4-week history of diarrhea.  He has no blood in the stools.  The patient recently returned from a trip to South America, where he developed foul-smelling stools, abdominal cramps, and bloating.  A 3-day course of ciprofloxacin did not relieve his symptoms.  He has no previous medical problems and has never had similar symptoms.  The patient takes no other medication and does not use tobacco, alcohol, or illicit drugs.  Temperature is 36.8 C (98.2 F), blood pressure is 126/80 mm Hg, and pulse is 86/min.  Examination shows a soft, nontender abdomen with increased bowel sounds.  Which of the following is the most appropriate next step in management?

Quizplus · Accepted Answer

This patient has typical features of giardiasis, including diarrhea acquired during international travel, abdominal cramps, foul-smelling stools, bloating, and benign findings on abdominal examination. Giardia duodenalis (sometimes noted as G lamblia or G intestinalis) is common in rural areas and developing countries, and has an incubation period of 1-2 weeks. It is most commonly transmitted by contaminated water but can be foodborne or transmitted person-to-person via a fecal-oral route. Most patients are asymptomatic; however, a significant minority of those who do develop clinical illness may go on to develop chronic giardiasis characterized by malabsorption, weight loss, or persistent gastrointestinal distress. The preferred confirmatory test for giardiasis is a stool antigen assay (direct immunofluorescence or ELISA). Stool microscopy for oocysts and trophozoites can also identify the organism and is useful in resource-poor settings or if other parasitic organisms are suspected. Some facilities also offer a nucleic acid amplification assay. Metronidazole is the preferred treatment. Asymptomatic carriers do not usually need treatment. oocysts trophozoites (Choice A) A short course of ciprofloxacin is advised for empiric treatment of traveler's diarrhea (most commonly due to Escherichia coli). However, the preferred treatment for giardiasis is metronidazole. Diagnostic confirmation should be obtained prior to additional antibiotic therapy in this patient with a prolonged course of diarrhea who has failed ciprofloxacin. (Choices B and F) Upper endoscopy with small bowel biopsy (to rule out tropical sprue) and colonoscopy would be considered in patients with persistent diarrhea who remain undiagnosed after initial noninvasive testing (eg, microscopy, stool antigen testing). (Choice C) CT imaging is not useful in routine evaluation of travel-associated diarrhea. (Choice D) Clostridium difficile causes antibiotic-associated colitis. This patient was symptomatic prior to receiving antibiotics, so C difficile would be less likely. Educational objective: Giardiasis is characterized by persistent diarrhea and abdominal cramps, and is most commonly transmitted via water in rural areas and developing countries. The preferred diagnostic test is a stool antigen assay. Metronidazole is the first-line treatment.

A 34-Year-Old Man Comes to the Office with a 4-Week