Magnetic resonance imaging detected renal volume reduction in refluxing and nonrefluxing kidneys

Renal parenchymal damage is a well recognized sequela of urinary tract infection in the setting of vesicoureteral reflux. We investigated renal magnetic resonance imaging as a quantitative modality to detect renal parenchymal damage in children with primary vesicoureteral reflux and urinary tract infection.

We retrospectively reviewed the medical records of children with primary vesicoureteral reflux and urinary tract infection who underwent renal magnetic resonance imaging evaluation. Those with other genitourinary pathology were excluded. Controls underwent magnetic resonance imaging for nongenitourinary pathologies. Kidneys were segregated among control, nonrefluxing, and low grade (I to III) and high grade (IV to V) reflux. Size plots (magnetic resonance imaging volume vs age) were drawn for comparison. Gross imaging abnormalities observed were renal scarring and small size.

Magnetic resonance imaging was performed in 114 patients with vesicoureteral reflux (228 kidneys, patient age 0.5 to 17.8 years) and 21 controls (42, 0.5 to 12). Higher grades of reflux were associated with smaller volume, and smaller volume was noted in the refluxing and nonrefluxing kidneys of children with vesicoureteral reflux. Kidneys from patients with unilateral or bilateral reflux had significantly decreased renal volume compared to controls (p <0.0001). Kidneys in which vesicoureteral reflux spontaneously resolved had renal volumes similar to control kidneys (p = 0.23).

Use of magnetic resonance imaging derived renal volume allows renal comparison and is helpful in evaluating patients with vesicoureteral reflux. In patients with a history of a febrile urinary tract infection and reflux the finding of measurably smaller kidneys appears to be more common than scarring. Whether these findings represent renal atrophy or hypoplasia needs further investigation.