A 4-month-old uncircumcised male is brought to the emergency department with a 2-day history of high-grade fever (max 103.1°F / 39.5°C), irritability, and reduced oral intake. The mother reports that he vomited twice today after feeding. He has had fewer wet diapers than usual over the last 24 hours. There is no history of cough, rhinorrhea, or diarrhea. The patient was born at term with no complications, and the mother recalls that prenatal ultrasounds were normal. He has no known drug allergies and takes no medications. There is no family history of vesicoureteral reflux or renal disease.

The infant is ill-appearing, irritable but consolable. Capillary refill time 2 seconds. Temperature is 102.9^o F (39.4^o C), heart rate is 160 bpm, respiratory weight is 40/min, and blood pressure is 90/55 mm Hg. His weight is 6.8 kg.