Variability of diuresis renography interpretation due to method of post-diuretic renal pelvic clearance half-time determination

Purpose: We assessed variability in the interpretation of diuresis renograp hy that may result from using different methods of clearance half-time dete rmination. Materials and Methods: We reviewed 152 diuresis renography studies performe d at diagnosis or during followup of 53 children enrolled in a prospective study assessing the natural history of unilateral neonatal hydronephrosis. Studies were classified as nonobstructive, indeterminate or obstructive usi ng 4 methods of half-time determination. Intermethod correlation and agreem ent were evaluated. We compared the proportion of nonobstructive, indetermi nate and obstructive classifications by each method, and the interpretation of individual studies based on each method. Results: Among methods we noted a high degree of correlation and fair to ex cellent agreement (Spearman rho = 0.86 to 0.92 and kappa = 0.57 to 0.86, re spectively). However, in 27.8% of intermethod comparisons the proportion of studies classified as nonobstructive, indeterminate and obstructive differ ed significantly (p <0.05). The classification of pelvicaliceal drainage va ried by method for all but the most severely dilated systems. In individual studies classification by 1 method was discordant with classification by a nother in 19% of comparisons. Of the discordant interpretations 97.7% invol ved nonobstructive versus indeterminate or indeterminate versus obstructive classifications. Conclusions: Variability in classifying drainage patterns based on half-tim e requires that practitioners be circumspect when applying this parameter f or managing asymptomatic hydronephrosis. It also necessitates the descripti on of quantitative methodology in published series of this important clinic al problem.