An 8-year-old boy is brought to the clinic due to 10 days of profuse diarrhea and abdominal cramps. His stools are foul-smelling and appear nonbloody and oily; volume and frequency have been persistent. The patient tolerates liquids but has had minimal solid food due to lack of appetite. Prior to these symptoms, he was well except for an episode of acute otitis media for which he completed a course of amoxicillin last month. The patient recently returned a few weeks ago from a vacation at his family's lake house. Weight is 30.4 kg (67 lb), a decrease of 2.3 kg (5 lb) from his annual checkup 3 months ago. He is afebrile. Abdominal examination reveals hyperactive bowel sounds but is otherwise normal, as is the remainder of the examination. Complete blood count is normal, and stool guaiac testing is negative. This patient's diarrhea is most likely due to which of the following mechanisms?

Question

An 8-year-old boy is brought to the clinic due to 10 days of profuse diarrhea and abdominal cramps.  His stools are foul-smelling and appear nonbloody and oily; volume and frequency have been persistent.  The patient tolerates liquids but has had minimal solid food due to lack of appetite.  Prior to these symptoms, he was well except for an episode of acute otitis media for which he completed a course of amoxicillin last month.  The patient recently returned a few weeks ago from a vacation at his family's lake house.  Weight is 30.4 kg (67 lb), a decrease of 2.3 kg (5 lb) from his annual checkup 3 months ago.  He is afebrile.  Abdominal examination reveals hyperactive bowel sounds but is otherwise normal, as is the remainder of the examination.  Complete blood count is normal, and stool guaiac testing is negative.  This patient's diarrhea is most likely due to which of the following mechanisms?

Quizplus · Accepted Answer

11ec25c8_d26c_6a7b_bc81_2711a5be4186_MD0003_00 This patient has acute weight loss and profuse, oily, nonbloody diarrhea after a recent lake vacation, findings concerning for giardiasis. Giardia duodenalis (ie, G lamblia, G intestinalis) is a protozoan parasite transmitted via the fecal-oral route from person-to-person or by contaminated water or food. G duodenalis is endemic in low-resource settings and is a frequent cause of travel-associated diarrhea. In high-resource settings, the most common risk factor is exposure to cysts shed by infected mammals into rivers and lakes, which is the most likely source of this patient's illness. Pathogenesis involves disruption of the epithelial tight junctions between enterocytes within the small intestine, leading to symptoms of malabsorption. Although some patients may be asymptomatic, acute giardiasis commonly presents with nonbloody, foul-smelling, greasy or oily diarrhea 1-2 weeks after exposure. Patients may also have abdominal cramping, bloating/flatulence, and acute weight loss. Symptoms usually self-resolve within a month. Stool antigen or nucleic acid amplification testing is diagnostic. Treatment is with tinidazole and is typically recommended for asymptomatic patients with high risk of disease spread (ie, child in day care) or any symptomatic patients. If untreated, a minority of patients develop chronic giardiasis and malabsorption, resulting in profound weight loss, poor growth in pediatric patients, and vitamin deficiencies. (Choice A) Enterotoxin-mediated Escherichia coli is a common cause of travelers' diarrhea. Symptoms most commonly develop during international travel due to a short incubation period and include self-limiting, watery diarrhea lasting <5 days, unlike this patient. (Choices C and E) Ulcerative colitis is characterized by mucosal inflammation and erosion of the colon, and Crohn disease shows transmural inflammation of the entire gastrointestinal tract. These two forms of inflammatory bowel disease can present with prolonged diarrhea and weight loss. However, patients usually have abdominal tenderness on examination during a flare, and anemia, leukocytosis, and positive stool guaiac are typical. (Choice D) Cystic fibrosis causes pancreatic insufficiency and fat malabsorption, which leads to symptoms of oily, nonbloody diarrhea and weight loss. However, most patients begin to develop pancreatic insufficiency by age 1, not acutely as in this case. In addition, a history of chronic pulmonary infections would be expected. Educational objective: Giardia duodenalis disrupts the epithelial tight junctions between small intestinal enterocytes, leading to acute malabsorption (eg, oily, nonbloody, foul-smelling diarrhea) typically lasting up to a month. Left untreated, chronic giardiasis can result in severe weight loss and vitamin deficiencies. References: Giardia lamblia enteritis. (http://www.ncbi.nlm.nih.gov/pubmed/30285390)

An 8-Year-Old Boy Is Brought to the Clinic Due to 10