Imagine a busy day on an inpatient service when a young patient with a straightforward febrile urinary tract infection (UTI) is admitted on appropriate antibiotics. You’re confident in the next steps—according to the 2011 AAP UTI guidelines1, a renal and bladder ultrasound (RBUS) should be ordered to detect anatomic abnormalities, such as hydronephrosis, suggestive of vesicoureteral reflux (VUR). If these are present, the next step would be to perform a voiding cystourethrogram (VCUG). But—is there an optimal time during the acute illness to order the RBUS? Could factors related to acute illness cause renal pelvis dilation that mimics, but is not true, hydronephrosis? And what considerations should be made for patients with negative urine culture?
Abnormal dilation on RBUS suggests the need for a follow-up VCUG to further characterize if VUR is occurring. Early detection of high grade VUR may prevent recurrent UTI, renal scarring, and, ultimately, chronic kidney disease.2 However, VCUG carries risk: it is invasive, involves radiation exposure, is costly, and can be quite traumatic for patients and families.3 Additionally, renal pelvis dilation early in an acute illness may be caused by edema and acute inflammation from the pathogens themselves1.
The answers to these questions are explored in an upcoming paper in Hospital Pediatrics by Rainey et al., entitled “Predictors of Abnormal Renal Ultrasonography in Children with Urinary Tract Infection. (10.1542/hpeds.2023-007557). This is a 5-year, multi-center, retrospective observational study looking at patients aged 2–24 months presenting with their first UTI who underwent a RBUS to evaluate the effect of timing of renal imaging relative to acute illness.
After retrospectively viewing the charts of 333 included patients, the study found that longer time between acute infection and RBUS was associated with lower odds of detecting abnormal dilation. Approximately 41% of patients had abnormal dilation on RBUS, with mean time to RBUS being around 15 days after acute infection. In patients that underwent follow up imaging, over 50% showed spontaneous resolution of dilation. One hundred and ninety-two underwent VCUG, and 43.8% had some degree of VUR, while 18.2% had high grade VUR (Grade IV or V). Interestingly, a notable portion of patients (32%) who underwent RBUS did not have positive urine culture nor fever. An explanation for this may be due to a limitation of the study; records from outside facilities were not reviewed, leaving open the possibility that some cultures were pre-treated with antibiotics. Another limitation of this paper is that pyuria on urinalysis was not included into the definition of UTI.
This paper contributes valuable insights to the expanding research on best practices for managing febrile UTIs in young patients. In our own practice, RBUS is usually performed earlier than the timeline proposed in the study. Future research could further refine the ideal timing for imaging—balancing the need for high-value care with the importance of avoiding complications from high grade VUR. As for our newly admitted patient with UTI, we might just wait a little longer than we previously did to get that RBUS.
References
- Roberts KB, Subcommittee on Urinary Tract Infection, Steering Committee on Quality Improvement and Management. Urinary Tract Infection: Clinical Practice Guideline for the Diagnosis and Management of the Initial UTI in Febrile Infants and Children 2 to 24 Months. Pediatrics. 2011;128(3):595-610. doi:10.1542/peds.2011-1330
- Massanyi EZ, Preece J, Gupta A, Lin SM, Wang MH. Utility of Screening Ultrasound After First Febrile UTI Among Patients With Clinically Significant Vesicoureteral Reflux. Urology. 2013;82(4):905-909. doi:10.1016/j.urology.2013.04.026
- La Scola C, De Mutiis C, Hewitt IK, Puccio G, Toffolo A,et al; Different Guidelines for Imaging After First UTI in Febrile Infants: Yield, Cost, and Radiation. Pediatrics March 2013; 131 (3): e665–e671. 10.1542/peds.2012-0164
