What to Do If a Febrile Urinary Tract Infection Occurs After Treatment

A urinary tract infection diagnosis in a feverish child is not made from urinalysis alone; a urine culture must be obtained from a reliable sample before antibiotics are started. In an infant wearing diapers, a bag sample is used only to rule things out; a catheter sample is used for culture. In a toilet-trained child, a mid-stream sample is enough.

In the first months after injection or reimplantation, the first cause of a febrile infection that must be ruled out is ureteral obstruction; a blocked, infected kidney can be damaged quickly. For this reason, a kidney-bladder ultrasound is performed without delay when fever starts, and compared with the previous ultrasound.

A febrile UTI after endoscopic injection raises the possibility that the bulking agent was insufficient or of late recurrence (reported in the literature at approximately 10–20%); for this reason, once the infection is treated, reflux is reassessed with a VCUG (voiding cystourethrogram; the “catheter film”) or ceVUS (contrast-enhanced voiding urosonography). If the follow-up study hasn't been done yet, its timing can be moved up.

In a child who has completed toilet training, the most common cause of a febrile infection after treatment is not reflux itself but constipation, delaying urination, urgency, and incomplete bladder emptying (BBD). In the RIVUR and CUTIE studies, the group with the highest rate of recurrent infection was children with BBD; even if injection or surgery corrects the reflux, infection can persist if BBD is not treated.

• Are bowel movements fewer than 3 times a week, or hard and painful?
• Does the child delay urinating, hold it in with urgency, or have accidents?
• Do the feet reach the floor on the toilet, is sitting comfortable?
• How many times a day, and how much urine, does the child pass (voiding diary)?
• Is there residual urine after voiding on ultrasound?

There is no method that can show, in the acute phase, whether a febrile infection has left a lasting mark (scar) on the kidney; DMSA (renal scan) findings in the acute period can be temporary. For this reason, DMSA is planned about 4–6 months after the infection and compared with any previous scan.

In the following situations, seek care the same day without waiting to obtain a culture; a young infant with a febrile UTI may need to be hospitalized.

• Fever of 38°C or higher in an infant under 3 months.
• Fever together with flank pain, vomiting, or lethargy.
• Fever in the first weeks after the procedure (obstruction must be ruled out).
• Fever that does not respond to antibiotics within 48 hours.
• A marked decrease in urine output, or inability to urinate.