Ultrasound Estimation of Female Bladder Volume Based on Magnetic Resonance Modeling

Purpose: We developed a precise method to noninvasively and conveniently measure female bladder volume greater than 100 ml by ultrasound. Materials and Methods: Using the proposed method bladder magnetic resonance measurements were made in 7 healthy women to create the volume estimation model. To validate the model for ultrasound application bladder ultrasound images were scanned in 23 healthy women and corresponding volumes were calculated. Calculated and true volumes were compared with the Pearson correlation coefficient and Bland-Altman plots. Results: A total of 51 bladder magnetic resonance images were segmented and reconstructed as 3-dimensional objects. Of the 51 objects 24 had a volume of greater than 100 ml. Based on the 24 objects we regressed the new equation, V = 7.1 × Dl × H - 23, where V represents estimated volume, Dl represents bladder depth and H represents bladder height measured by the proposed method. The estimation was statistically significant (SE 44, r² 0.94, p <0.001). A total of 69 ultrasound measurements were made and corresponding volumes were calculated by the equation. The sum of voided and post-void residual volume, when there was any, was considered true volume (range 140 to 995 ml). A significant relationship was found between true and calculated volume (mean difference -3 ml, mean absolute difference 23, r² = 0.97, p <0.01). The Bland-Altman 95% limits of agreement were -57 to 51 ml. Conclusions: The proposed method performs well to estimate female bladder volume greater than 100 ml.