Diagnosis:
Depends on culture of bacteria from the urine.

(a) Urine collection:
1. Mid stream sample is ideal in toilet trained children. Preliminary cleaning of the perineum with clean water is sufficient.
2. Suprapubic bladder puncture is the method of choice in sick infants. There is little risk and any bacteria grown is abnormal.
3. Catheter specimen – a disposal polythene infant feeding tube may be used. If done shortly after voiding the residual urine in the bladder can be measured.
4. Perineal collecting bag after disinfection of the skin of the genitalia. The bag should be removed as soon as urine is passed. Specificity of these cultures is lower than that of a midstream specimen.

(b) Storage and transport: The sample should be plated within half an hour of collection or stored in a refrigerator in a sealed container (for maximum 48 hours). Because of urethral contamination a significant culture is defined as >10000

organisms/ml in a clean catch specimen, >1000 organisms/ml in a catheter specimen and any growth in a suprapubic aspirate. A lower count is significant in young infants, in those who have received treatment, in symptomatic individuals and in those on diuretic therapy. Mixed growth suggests contamination. Urinalysis should be obtained from the same specimen as culture. Pyuria suggests infection but is not diagnostic. Microscopic hematuria is common in acute cystitis. Casts in the urinary sediment suggest renal involvement. Proteus infection consistently produces an alkaline pH.
With acute renal infection leucocytosis, neutrophilia and raised ESR and CRP are common. Since sepsis is common in renal infection especially in infants and in those with obstruction blood culture and sensitivity should be obtained during febrile infection. UTI in children cannot be excluded by a negative dipstick nitrite and leukocyte esterase test