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 × width × height × 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.
Keywords: Bladder volume; Inter-rate reliability; Post-void residual urine volume; Reproducibility of tests; Ultrasonography; Urinary bladder.