<1 month old
Toxic
Inability to tolerate POs
1mo - 2yr, who are well-appearing and not vomiting
24-hour follow up
>2 years old
48-hour follow up
24-hour follow up
48-hour follow up
Urinary tract infection 
Emergent
Pyelonephritis
Necrotizing Enterocolitis
Acute cystitis
Volvulus
Bladder trauma
Testicular torsion