A 4-year-old girl developed acute-onset colicky abdominal pain, vomiting, and loose bloody stools during a family vacation. She was treated with supportive care and began to feel better. A few days later, her parents bring her to the emergency department because she has urinated only once in the past 10 hours and the urine was red. Physical examination shows conjunctival pallor but is otherwise normal. Laboratory studies are as follows: Urinalysis shows proteinuria and hematuria. Which of the following mechanisms is the most likely cause of this patient's condition?

Question

A 4-year-old girl developed acute-onset colicky abdominal pain, vomiting, and loose bloody stools during a family vacation.  She was treated with supportive care and began to feel better.  A few days later, her parents bring her to the emergency department because she has urinated only once in the past 10 hours and the urine was red.  Physical examination shows conjunctival pallor but is otherwise normal.  Laboratory studies are as follows:  Urinalysis shows proteinuria and hematuria.  Which of the following mechanisms is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_3a3b_03d3_9249_770fadb6a7a5_MD0001_00 This patient has diarrhea-associated hemolytic uremic syndrome (HUS), a major cause of acute renal failure in young children. Most cases are due to intestinal infection by Shiga toxin (verotoxin)-producing organisms (eg, Escherichia coli O157:H7, Shigella dysenteriae). These toxins injure the endothelium of preglomerular arterioles and glomerular capillaries, leading to platelet activation and aggregation and the formation of microthrombi. Platelet consumption causes thrombocytopenia (platelets <140,000/mm³), but there is typically no purpura or active bleeding. Erythrocytes passing through the damaged capillaries suffer shear injury and are broken down to schistocytes, causing microangiopathic hemolytic anemia (conjunctival pallor). Extensive damage to the renal vasculature results in acute kidney injury (oliguria/anuria, hematuria, increased creatinine). (Choice B) Poststreptococcal glomerulonephritis develops approximately 1-3 weeks following a cutaneous or pharyngeal infection by a nephritogenic strain of group A β-hemolytic streptococci. It is caused by an immune response against streptococcal antigens that deposit in the glomerulus. Patients have oliguria, hematuria, proteinuria, edema, and hypertension. Anemia is not commonly seen. (Choice C) Henoch-Schönlein purpura (HSP) is a systemic leukocytoclastic vasculitis caused by IgA immune complex deposition within small blood vessels of the skin, kidneys, intestines, and joints. Symptoms include palpable purpura, abdominal pain, arthralgias, and acute glomerulonephritis. Platelet count and coagulation studies are normal in HSP. In addition, the absence of palpable purpura and joint symptoms makes HSP an unlikely diagnosis in this patient. (Choice D) Kawasaki disease (mucocutaneous lymph node syndrome) is a vasculitis of medium arteries that classically affects young children. The main symptoms are high fever, conjunctivitis, cervical lymphadenopathy, periungual desquamation, and mucocutaneous changes (eg, strawberry tongue). (Choice E) Disseminated intravascular coagulation refers to massive, widespread activation of the coagulation cascade due to release of procoagulant substances caused by sepsis, malignancy, or trauma. These patients usually have bleeding, petechiae, and bruising due to concomitant fibrinolysis and consumption of platelets and coagulation factors. Educational objective: Hemolytic uremic syndrome is a common cause of acute renal failure in children. It is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Most cases develop following a diarrheal illness caused by Shiga toxin-producing organisms (eg, Escherichia coli O157:H7, Shigella dysenteriae). __________ References: Shiga toxins and the pathophysiology of hemolytic uremic syndrome in humans and animals. (http://www.ncbi.nlm.nih.gov/pubmed/23202315) HUS and TTP in children. (http://www.ncbi.nlm.nih.gov/pubmed/24237985)

A 4-Year-Old Girl Developed Acute-Onset Colicky Abdominal Pain, Vomiting, and Loose