Sonographic assessment of the effect of vesicoureteral reflux and urinary tract infections on growth of the pediatric solitary kidney.

INTRODUCTION

Perusal of recent guidelines relating to proper evaluation of infants and children with urinary tract infection (UTI) suggests that the occurrence of vesicoureteral reflux (VUR) may not have the clinical import previously ascribed to this anatomic abnormality. Patients with a solitary kidney uniquely allow investigation of the effects of both vesicoureteral reflux (VUR) and urinary tract infection (UTI) on renal growth unencumbered with the inevitable questions of laterality that confound analysis in patients with two kidneys. Several previous studies with conflicting results have addressed whether vesicoureteral reflux (VUR) impacts ultimate renal size in children with a solitary kidney. Few published studies have considered the occurrence of both urinary tract infection (UTI) and VUR on the degree of compensatory hypertrophy. This is the largest series to date investigating the effect of both UTI and VUR on the degree of compensatory hypertrophy with time.

OBJECTIVE

Our objective was to analyze sonographically determined renal growth in patients with a solitary kidney, stratifying for both the occurrence and severity of UTIs and the occurrence and severity of VUR.

STUDY DESIGN

We retrospectively reviewed the clinical history (including bladder and bowel dysfunction (BBD)) and radiology reports of 145 patients identified as having either a congenital or acquired solitary kidney in our pediatric urology practice from the prior 10 years. UTIs were tabulated by severity, where possible, and the grade of VUR was recorded based on the initial cystogram. Sonographically determined renal length was tabulated for all ultrasounds obtained throughout the study. Based on a mixed-effects model, we investigated the influence of UTI and VUR on renal growth.

RESULTS

Of the 145 patients analyzed, 105 had no VUR and 39 had VUR (16 = Gr I&II, 11 = GIII, 12 = GIV&V). Comparison showed that there was no difference in the occurrence of UTI between those without VUR (27/105 with UTI) and those with VUR (15/39 with UTI; p = 0.14). There was no difference in the occurrence of BBD in patients with VUR (15/39) and those without VUR (36/106, p = 0.62). While neither VUR nor UTI alone affected renal growth in the solitary kidney, the three-way interaction term among age, VUR, and UTI was significant (p = 0.016). The growth of the kidneys in the various patient groups is depicted in the table. From the analysis, a refluxing solitary kidney with UTI showed a significantly lower growth rate than the other groups (p < 0.001).

DISCUSSION

This study is limited by the inherent selection bias of retrospective studies. Additionally, the variability of sonographic renal measurement is well recognized. Lastly, our sample size did not allow us to incorporate the severity of the UTIs and the grades of VUR in our final regression model. Nevertheless, the overall patterns suggest that when both VUR and UTI are present, the solitary kidney demonstrates less renal growth with time. Study of larger cohorts of patients with solitary kidneys will be necessary to confirm our observations and discern what, if any, are the consequences of high-grade VUR and upper tract UTI in these patients.

CONCLUSION

In the largest series to date we were able to discern no independent effect of either VUR or UTI on sonographically determined renal growth in patients with a solitary kidney. However, UTI and VUR together result in kidneys that are smaller than other solitary kidneys not so affected. Follow-up studies of larger cohorts seem warranted to confirm these findings and discern the clinical import of these smaller kidneys.