Primary vesicoureteral reflux detected in neonates with a history of fetal renal pelvis dilatation

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Mar 8 2006

Fetal renal pelvis dilatation is a common abnormality, observed in 4.5% of pregnancies but surrounded by controversy regarding its significance. Working up renal pelvis dilation has become a standard of care regardless of the presence or absence of symptoms with vesicoureteral reflux (VUR) being one of the primary concerns.

This prospective cohort study by Ismaili et al was performed to try to establish the incidence and clinical evolution of primary VUR diagnosed at birth as a result of a systematic screening of fetal renal pelvis dilatation along with changes in calculated glomerular filtration rate (GFR) in the affected moieties.

The group prospectively followed 43 infants with primary VUR identified from among a cohort of 497 infants with fetal renal pelvis dilatation. Postnatal renal ultrasound (US) examinations were performed at 5 days and 1, 3, 6, 12, and 24 months of life. Voiding cystourethrography was performed in the neonatal period and repeated at 12 and 24 months when VUR was persistent. They performed 2 radioisotopic examinations, including a 99mTc-MAG3 renogram and a plasma clearance of Cr-51 EDTA, in all children with high-grade reflux.

They found the incidence of VUR was 9%. Among the 43 patients followed, 11 (26%) had high-grade (IV-V) VUR and 32 (74%) had low-grade VUR. Resolution of reflux occurred in 2 of 11 (18%) patients with high-grade VUR and in 29 of 32 (90.6%) patients with low-grade VUR by 2 years of age (P < .001). At 2 years of age, 91% of the low-grade refluxing kidneys were normal on US, compared with only 35% of the high-grade refluxing kidneys. Split renal function was within normal range and single-kidney GFR was significantly increased in 13 of the 17 high-grade refluxing kidneys during follow-up. They claim that there was a strong association between dysplasia on US and poor renal function outcome. This is a little tricky since dysplasia is a pathologic diagnosis but can be assumed if there is a focal abnormality on DMSA renal scans prior to any episodes of pyelonephritis in the newborn period. US is not an accurate determination of dysplasia or scarring. After the newborn period, these findings even on DMSA may be further confounded by “silent pyelonephritis”…another area of controversy.

Overall, a well-written study with the conclusion that most infants with VUR have a low grade and it resolves rapidly. The group also concluded that in children with high-grade VUR, spontaneous resolution is rare by 2 years old, but persistent reflux rarely impairs the renal function. The bottom line…a nicely executed confirmation of what most of us feel is known dogma.

By Pasquale Casale, MD

Reference:

The Journal of Pediatrics. 148(2): 222-227, February 2006.