Four-Dimensional Ultrasonography for Dynamic Bladder Shape Visualization and Analysis During Voiding

Objective. The purpose of this study was to describe initial applications of 4‐dimensional ultrasonography (4DUS) for visualizing dynamic change in 3‐dimensional (3D) bladder shape as well as for analyzing intravesical volume and diameters during voiding. Methods. In 15 healthy volunteers and 5 patients with lower urinary tract symptoms, 4DUS images of the bladder during voiding were obtained by transabdominal 4DUS and compared with the outcome of uroflowmetry. Changes of intravesical volume as well as diameters in axial, coronal, and sagittal planes were measured and analyzed in comparison with uroflow data. Results. Dynamic 3D visualization of the bladder shape was feasible in all 20 men. Multiplanar display of 4DUS showed dynamic 3D images of the bladder during voiding to be simultaneously visualized in the axial, coronal, and sagittal planes. The change and decrease rate in intravesical volume calculated by 4DUS data had significant correlation with the average flow rate (P = .02) and the maximum flow rate (P = .04), respectively. Among the 3 diameters, the change of coronal diameter was significantly most correlated with change of the intravesical volume (P < .0001). The change in coronal diameter, which was observed in patients with urinary disturbance, had a significant difference compared with those observed in control subjects (P = .01). Conclusions. Monitoring of voiding with 4DUS was feasible in healthy men and patients with lower urinary tract symptoms. Four‐dimensional ultrasonography has the potential to be a novel noninvasive urodynamic modality to visualize dynamically the lower urinary tract during voiding and to improve pathophysiologic understanding of voiding.