A 24-year-old man comes to an urgent care center because of a 2 week history of watery diarrhea. The patient's stools are pale, voluminous, foul smelling, and non-bloody. He has lost 5 pounds (2.3 kg) over the past week despite eating normally. He denies fever or abdominal pain, but does admit to bloating and flatulence. He is an avid hiker, but denies recent travel.
His vital signs are within normal limits. His abdomen is soft and non-tender with normal bowel sounds. The remainder of his examination shows no abnormalities.
Laboratory results are as follows:

Which of the following is the most appropriate next step in management?

Question

A 24-year-old man comes to an urgent care center because of a 2 week history of watery diarrhea.  The patient's stools are pale, voluminous, foul smelling, and non-bloody.  He has lost 5 pounds (2.3 kg) over the past week despite eating normally.  He denies fever or abdominal pain, but does admit to bloating and flatulence.  He is an avid hiker, but denies recent travel.
His vital signs are within normal limits.  His abdomen is soft and non-tender with normal bowel sounds.  The remainder of his examination shows no abnormalities.
Laboratory results are as follows:

Which of the following is the most appropriate next step in management?

Quizplus · Accepted Answer

This patient's presentation of diarrhea with steatorrhea (indicating malabsorption) is most likely due to Giardiasis. Giardia cysts survive well in cold water (e.g., rivers and streams), and water dwelling mammals (e.g., beavers) can become infected and continue infecting the water. Hikers in wilderness areas are at high risk for giardiasis if they drink water without adequate filtration, treatment, or boiling. Patients may be asymptomatic or present with the symptoms in the above table. Stool microscopy testing for G. lamblia trophozoites and cysts is initially preferred and can detect 50-70% of cases after one specimen and > 90% of cases after 3 specimens. Immunoassays for G. lamblia antibodies are more sensitive and specific than stool microscopy and can be performed if stool microscopy is negative. If noninvasive tests fail to reveal the organism, both endoscopy with duodenal biopsy and colonoscopy are very sensitive and specific for diagnosing G. lamblia. Stool microscopy (Choice A) Increased absolute eosinophil count (usually > 2000 cells/mm³) may suggest eosinophilic gastroenteritis, which is an uncommon cause of malabsorption. The diagnosis is confirmed with a biopsy demonstrating > 20-25 eosinophils/hpf. However, infectious etiologies should first be ruled out in this patient. ³ (Choice B) Colonoscopy with biopsies can confirm diagnoses such as celiac sprue, inflammatory bowel disease, and microscopic colitis. However, it is usually indicated after negative or equivocal noninvasive testing. (Choice C) Fecal fat testing will confirm malabsorption but it will not diagnose the underlying cause of the patient's diarrhea. (Choice E) Tissue transglutaminase IgA antibodies are frequently positive in celiac disease, which can present with malabsorption. However, this test should only be performed if the initial infectious studies are negative. Educational objective: Patients presenting with acute diarrhea associated with steatorrhea should first be evaluated for infectious etiologies. Giardia lamblia (also known as intestinalis or duodenalis) is the most common infectious cause of malabsorption and is diagnosed with stool microscopy or stool immunoassay. __________ References: Comparison of microscopy, real-time PCR and a rapid immunoassay for the detection of Giardia lamblia in human stool specimens. (http://www.ncbi.nlm.nih.gov/pubmed/17949440) An updated review on Cryptosporidium and Giardia (http://www.ncbi.nlm.nih.gov/pubmed/16880067) Giardia duodenalis: the double-edged sword of immune responses in giardiasis. (http://www.ncbi.nlm.nih.gov/pubmed/20599999)

A 24-Year-Old Man Comes to an Urgent Care Center Because