Modification and duration of intravenous therapy for acute pyelonephritis in children

Fever may take 48 to 72 hours to resolve in acute pyelonephritis, but children may systemically improve before then. If the child is not improving clinically within 48 hours of starting appropriate antibiotics, request a renal ultrasound; do not request an ultrasound for persistent fever alone (see Imaging to investigate UTI in children). Also consider if the child is at risk of a UTI caused by multidrug-resistant gram-negative bacteria, and reconsider the diagnosis of pyelonephritis.

Modify therapy for acute pyelonephritis in children based on the results of culture and susceptibility testing.

If the results of susceptibility testing are not available by 72 hours after the initial empirical antibiotic dose, intravenous therapy is still required, and gentamicin or tobramycin was used initially, switch to either ceftriaxone or cefotaxime (as above).

If the isolate is shown to be susceptible, and further intravenous therapy is needed, replace the empirical regimen with:

1amoxicillin 50 mg/kg up to 2 g intravenously, 6-hourly amoxicillin

OR

1ampicillin 50 mg/kg up to 2 g intravenously, 6-hourly. ampicillin

Switch to an oral antibiotic regimen once the child is clinically stable and able to tolerate or absorb oral therapy – see Guidance for intravenous to oral switch. Oral therapy should be based on the results of culture and susceptibility testing. If the results of susceptibility testing are not available, see Oral antibiotic therapy for acute pyelonephritis in children for oral regimens.

The total duration of therapy (intravenous + oral) for acute pyelonephritis in children is 7 to 10 days, depending on clinical response, antibiotic used and route of administrationMcAteer, 2023McMullan, 2016Schroeder, 2016McTaggart, 2015. A duration of 7 days is reasonable ifMcAteer, 2023:

  • intravenous therapy with a beta-lactam antibiotic (eg ceftriaxone, cefotaxime, amoxicillin) is used for the entire course
  • ciprofloxacin or trimethoprim+sulfamethoxazole is used for oral continuation therapy.

For all other patients, the total therapy duration (intravenous + oral) is 10 days.

For children with ongoing pyelonephritis symptoms following appropriate antibiotic therapy, seek expert advice.

Do not perform post-treatment urine culture to confirm resolution of infection for asymptomatic children.