Infants/young children: fever without other source
Older children:
Dysuria, frequency, or other<unk>  complaints
+/- abdominal/back pain
UTI + fever = pyelonephritis
Dysuria, frequency, or other<unk>  complaints
+/- abdominal/back pain
Urinary tract infection 
Emergent
Pyelonephritis
Necrotizing Enterocolitis
Acute cystitis
Volvulus
Bladder trauma
Testicular torsion