A 7-year-old boy is brought to the emergency department due to fatigue. One week ago, he developed abdominal pain, vomiting, and diarrhea. A few days later, he noticed significant blood in his stool, which has since resolved. The patient had been feeling better until today, when his mother noticed that he did not want to get out of bed. Despite drinking a normal amount of fluids, the patient has not urinated in 24 hours. Multiple family members had similar initial gastrointestinal symptoms after attending a family cookout last week, but they have all recovered. On physical examination, there is scleral icterus and 2+ pedal edema. Which of the following laboratory abnormalities is most likely associated with this patient's current condition?

Question

A 7-year-old boy is brought to the emergency department due to fatigue.  One week ago, he developed abdominal pain, vomiting, and diarrhea.  A few days later, he noticed significant blood in his stool, which has since resolved.  The patient had been feeling better until today, when his mother noticed that he did not want to get out of bed.  Despite drinking a normal amount of fluids, the patient has not urinated in 24 hours.  Multiple family members had similar initial gastrointestinal symptoms after attending a family cookout last week, but they have all recovered.  On physical examination, there is scleral icterus and 2+ pedal edema.  Which of the following laboratory abnormalities is most likely associated with this patient's current condition?

Quizplus · Accepted Answer

11ec25c8_d69d_1bbe_bc81_636f5657973a_MD0003_00 This patient has fatigue, edema, and anuria after a bloody diarrheal illness; these findings raise concern for hemolytic uremic syndrome (HUS). HUS most commonly occurs after infection due to a Shiga toxin-producing strain of Escherichia coli (serotype O157:H7). This toxin invades and destroys the colonic epithelial lining, producing abdominal pain and bloody diarrhea, as seen in this patient. HUS typically presents about a week after the diarrheal illness with signs of anemia (eg, fatigue, pallor), thrombocytopenia (eg, bruising), and acute kidney injury (eg, oliguria, edema). The shearing of red blood cells by platelet microthrombi leads to microangiopathic hemolytic anemia with schistocytes on peripheral smear. Hemolysis is evidenced by decreased haptoglobin and increased indirect bilirubin, which can cause scleral icterus (as in this case) as well as jaundice (Choice E). schistocytes Treatment of HUS is supportive (eg, fluid/electrolyte management, blood transfusions, dialysis). Most patients improve within a few weeks. (Choice A) A decreased ferritin level is seen in iron deficiency anemia (eg, chronic gastrointestinal bleeding), which is unlikely in this patient with acute bloody diarrhea that is now resolved. Patients with HUS have normal or increased ferritin levels because ferritin is an acute-phase reactant that rises with inflammation. (Choice C) A decreased reticulocyte count in the setting of anemia indicates defective bone marrow (eg, viral suppression, aplastic anemia, malignancy). Reticulocyte counts are increased with hemolytic anemia. (Choice D) Disseminated intravascular coagulation occurs in severely ill patients (eg, sepsis) and is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and abnormal coagulation studies (ie, increased PT). HUS is more likely in this child with a preceding bloody diarrheal illness; PT is normal in HUS. (Choice F) The direct Coombs test is positive in patients with autoimmune hemolytic anemia, which can present with fatigue and indirect hyperbilirubinemia. However, signs of acute renal injury (eg, edema, anuria) would not be seen. Direct Coombs test is negative in HUS because red blood cells are mechanically destroyed. Educational objective: Hemolytic uremic syndrome, which is most commonly caused by a Shiga toxin-producing strain of Escherichia coli (serotype O157:H7), is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. References: Haemolytic uraemic syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/28242109)

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