Febrile Infection While on Antibiotic Prophylaxis (Breakthrough UTI)

A breakthrough UTI is a urinary tract infection with fever, confirmed by urine culture, that occurs despite regular use of antibiotic prophylaxis. A fever-free cystitis confined to the bladder, or asymptomatic bacteriuria, does not meet this definition; what matters is the presence of fever — that is, infection that has reached the kidney.

If a urine sample from a febrile child was collected with a bag, growth on culture may represent contamination; when the decision matters this much while on antibiotic prophylaxis, the reliability of the collection method is questioned. A culture obtained by catheter in an infant, or by clean-catch midstream urine in a toilet-trained child, showing significant growth, is required.

• At the same time, other possible sources of fever (ear, throat, viral infection) are assessed. A child whose fever is due to another cause and who has low-level growth in the urine should not be labeled as having a breakthrough UTI. The species of bacteria that grows and its antibiotic susceptibility also guide the next steps.

Once a breakthrough UTI is identified, the first step — before thinking about surgery — is to find the cause. Four categories are reviewed in order; more than one may be present at once.

• Adherence: is the medication given regularly, how many doses are missed?
• Dose: is it adequate for current weight, is the medication stored correctly?
• BBD: is there constipation, holding, or residual urine? (after toilet training)
• Resistance: is the bacteria that grew resistant to the prophylactic drug used?

After the infection is treated in a child with reflux who has had a febrile UTI, the kidney's condition is reassessed. In the acute phase, ultrasound is done to rule out complications such as dilation or abscess; for the question of scarring, DMSA (renal scan) is planned about 4–6 months after the infection, because a lack of uptake seen in the acute phase can be temporary.

• New scarring, or a drop in split function, found on DMSA is by itself a reason for corrective treatment. If there is no scarring and a correctable cause for the infection was found, surveillance under CAP can continue a while longer once that cause has been addressed; this decision is made together with the reflux grade, the child's age, and the family's preference.

When the cause of a breakthrough UTI cannot be corrected, or it recurs — especially if scarring is present — correcting the reflux itself becomes the priority. The goal is to end antibiotic-dependent surveillance and protect the kidney from further episodes. There are two main options, and our physicians perform both.

• Contact your physician right away: unexplained fever of 38°C or higher while on CAP
• Ask that a urine culture be obtained by an appropriate method before antibiotics are started
• Review the medication, dose, and toilet habits together after the infection
• Schedule the follow-up visit at 4–6 months, when DMSA and treatment options will be discussed again