A 5-year-old boy is admitted with fatigue, pallor, and decreased urine output following 3 days of bloody diarrhea. His mother reports he recently ate a salad containing raw spinach. Laboratory tests reveal hemoglobin 7 g/dL, platelets 65,000/μL, and creatinine 2.1 mg/dL. What is the most likely complication associated with this patient’s condition?