Caroline Helwick

October 20, 2012

October 20, 2012 (New Orleans, Louisiana) — In neonates younger than 2 months, voiding cystourethrograms (VCUGs) are not helpful in diagnosing urinary tract infection (UTI); therefore, urine culture should remain the standard diagnostic modality, according to a study from the University of Southern California (USC), Los Angeles.

"Reflux after the first UTI was uncommon in our select group of infants," said Mark Weems, MD, who presented the findings at the 2012 American Academy of Pediatrics (AAP) National Conference and Exhibition.

"Choosing to omit VCUG in infants less than 2 months old will not increase the risk of missing reflux compared to other children," he said.

The study aimed to determine whether the recently updated American Academy of Pediatrics (AAP) guidelines for the diagnosis and management of UTI are applicable to infants younger than 2 months. The guidelines state that diagnosis requires a positive urinalysis and culture with at least 50,000 colony-forming units (CFUs). Routine renal ultrasound is recommended, but VCUG is not. Test of cure is recommended only if sensitivities are not available.

"Premature infants and those less than 2 months of age, however, are excluded from these recommendations, and their management differs among physicians," Dr. Weems noted.

The concern, he said, is that prevalence of reflux has been reported to increase with younger age; therefore, cases of reflux might be missed in the absence of VCUG. The traditional approach has been to look for and treat reflux prophylactically with antibiotics to prevent subsequent UTIs, but the efficacy of this has been questioned.

"So our question was, Do we still need imaging if our treatments, based on the result, will not do any good?" he said.

Ten Years of Data

The study included all (N = 80) patients in the Los Angeles County and USC neonatal intensive care unit (NICU) with a UTI and a VCUG performed between 2000 and 2009. Median postmenstrual age was 39 weeks at diagnosis and 41 weeks at VCUG. UTI was defined as a positive urine culture that was treated.

The study found no association between prenatal ultrasound results and reflux with or without UTI. Reflux was observed in 18% of patients with a normal prenatal ultrasound and in 19% who had renal dilation.

The review also revealed the following:

  • Abnormal renal ultrasound was not associated with reflux when "abnormal" was defined as any renal dilation, or as hydronephrosis.

  • No measurements of renal pelvis anterior/posterior diameter were associated with increased risk for reflux on VCUG.

  • Renal dilation on prenatal ultrasound was strongly associated with postnatal renal dilation (P = .015).

It is interesting to note that several differences emerged when these younger infants were compared with the older group, which is the target of the AAP guidelines.

The neonates had significantly more abnormal ultrasounds and less reflux than children 2 to 24 months of age. Although the guidelines have suggested that 15% of ultrasounds are abnormal among older children, this study found 37% to be abnormal among the neonates (P < .001), and even though 34% of older children are believed to have reflux, only 20% of the younger children in this study had reflux (P = .018), Dr. Weems reported.

"Additionally, we showed that urinalysis, while valuable, is neither sensitive nor specific enough to be a reliable screening tool," Dr. Weems said.

The sensitivity of each urinalysis component was lower than in the older age group, but specificity was statistically equal. The exception was bacteria on urine microscopy, which was equally sensitive at lower CFUs but less specific. Sensitivity was 93% for cultures with more than 50,000 CFUs.

The sensitivity and specificity of any positive urinalysis were lower in this group than for ages 2 to 24 months, he added.

Finally, no level of elevated bilirubin or creatinine was associated with increased frequency of reflux, and all bacterial UTIs had a negative test of cure after treatment with appropriate antibiotics.

Ajay Talati, MD, professor of pediatrics and obstetrics and gynecology at the University of Tennessee, in Memphis, said this is "an important topic."

"This is uncharted territory for little babies," he said. "Most of the literature is for children 2 months and older. This kind of information definitely helps us avoid unnecessary investigations. Besides adding to cost, VCUG is pretty invasive and uncomfortable. This study suggests that VCUG won't tell us much more than renal ultrasound already shows, so there is no point to doing it."

Dr. Weems and Dr. Talati have disclosed no relevant financial relationships.

The American Academy of Pediatrics National Conference and Exhibition: Abstract 16842. Presented October 20, 2012.