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Background: Grading of VUR on the VCUG provides prognostic information in terms of spontaneous resolution of VUR and breakthrough UTIs. It has been used for decades as the gold-standard description of VUR, however, several recent studies demonstrated relatively low inter-rater reliability in grading VUR reflecting the subjectivity of the grading system. Grading of VUR is altered by the appearance of the intra-renal collecting system, however, the primary factors influencing resolution of VUR are more likely at the level of the distal ureter/bladder. We hypothesize that an increasing diameter of the distal ureter as measured on VCUG corresponds to an increasing abnormality of the ureteral orifice and intramural ureter and provides an objective measurement on VCUG predictive of clinical outcome. We also assessed its predictive ability compared to grade of VUR.
Methods: 147 initial VCUGs were reviewed of children diagnosed with primary VUR (124 girls; 23 boys; aged <1 month to 13.5 years old). The largest ureteral diameter within the pelvis was measured and then normalized by dividing it by the distance between the L1-L3 vertebral bodies to give the distal ureteral diameter: L1-L3 ratio (UDR). Other parameters evaluated included grade of VUR, laterality, age, gender, history of febrile UTI or multiple UTIs, and presence of bladder-bowel dysfunction. Clinical outcome at 2 years was defined as spontaneous resolution, persistent VUR or surgical correction.
Results: Average age at 1st VCUG was 2.7 years old (± 2.5 years). Mean age at VUR resolution was 5.3 years; mean time to resolution was 2.8 years. Of those who had surgical correction, mean age at operation was 5.7 years and mean time to operation was 3.0 years. As anticipated, there was a very high correlation between the UDR and VUR grade(P<0.0001). The mean UDR(SEM) for VUR grades 1-2, 3, 4, and 5 was 0.16(0.01), 0.25(0.01), 0.41(0.05), and 0.55(0.06), respectively. Also as anticipated higher grades of VUR, older age, and bilateral VUR were significantly associated with failure to spontaneously resolve VUR. Increasing UDR(per +0.1) was significantly associated with either persistent VUR or operation when adjusting for age, grade, laterality, and multiple UTIs as covariates with an OR of 1.73(1.02,2.95)(p=0.043) and 2.40(1.39,4.17)(p=0.002), respectively. When testing the effect of UDR and grade of reflux in the same model, UDR was noted to have a larger effect than grade (Wald Chi-Square 13.6; p=0.001 vs. 3.62;p=0.46, respectively).
Conclusions: Our findings demonstrate that the UDR obtained from the VCUG aids in predicting the clinical outcome of a child with VUR. UDR was highly correlated with grade of VUR but proved more predictive of resolution, persistence, or operative intervention than grade of VUR. The utility of the UDR include its improved objectivity compared to grading VUR, ready availability, and its ability to further stratify patients in terms of predicting clinical outcome thus permitting more individualizing patient management.Evaluation of the UDR with a larger multi-institutional study is warranted to confirm these findings and define specific values predictive of outcome in association with other known predictive factors.