Urine culture is considered the gold standard in the diagnosis of pediatric UTI. Criteria for a definite urinary tract infection depend on the technique used to obtain the urine culture. A positive culture is defined as: 102 CFU/mL of a single urinary pathogen obtained by suprapubic bladder aspiration, 104 CFU/mL of a single pathogen obtained by urethral catheterization, and 105 CFU/mL of a single pathogen from a midstream clean-catch specimen. Bag specimens are not recommended for infants and non–toilet-trained children because of their high degree of contamination. A urine dipstick or urinalysis may be negative in up to 50% of patients with UTI. Positive nitrite and leukocyte esterase on urine dipstick have the highest combined sensitivity and specificity for infection. A positive Gram stain of the urine has a sensitivity of 93%. A child or infant with fever and systemic signs and symptoms of UTI should be presumed to have pyelonephritis. Cystitis is associated with more local symptoms such as dysuria or suprapubic tenderness.