Intra- and inter-rater reliability of post-void residual bladder volume with ultrasound

Introduction and hypothesis The purpose of the present study was to test the intra- and inter-rater reliability of the measurement of post-void residual bladder volume using ultrasound. Methods Two evaluators performed three measurements of the height, width, and length of the empty bladder using ultrasound. The voiding residual volume was calculated using the equation: volume = length x width x height x 0.52. Intraclass correlations (ICC) were calculated considering: ICC >= 0.75 excellent, 0.40 <= ICC < 0.75 satisfactory, and ICC <0.40 poor, with a significance level of 5% and analysis of confidence intervals (95% CI). Results Twenty women participated, with an average age of 27.95 +/- 3.15 years. The inter-rater ICCs for height, width, and length were 0.96 (CI 0.89-0.98), 0.88 (CI 0.71-0.95), and 0.84 (CI0.60-0.94) respectively. For the intra-rater ICCs, the values were 0.97 (CI 0.95-0.99), 0.98 (CI 0.96-0.99), and 0.97 (CI 0.94-0.99) for evaluator 1 and 0.99 (CI 0.97-0.99), 0.97 (CI 0.94-0.99), and 0.95 (CI 0.90-0.98) for evaluator 2, for height, width, and length, respectively. The residual inter-test volume was 0.96 (CI 0.90-0.99) and the intra-test volume was 0.99 (CI 0.97-0.99). All analyses presented p < 0.0001. Conclusions The intra- and inter-rater reliability for both the post-void residual volume and measurement of the bladder dimensions showed excellent agreement.