Can We Trust the Math? Correlation of Objective Postvoid Residual With Calculated Subtraction Postvoid Residual.

Objective: The aim of the study was to determine the accuracy of postvoid residual (PVR) by subtraction as compared with objective measurement by bladder scan or catheterization.

Methods: This is a secondary analysis of postoperative patients who underwent avoiding trial by retrograde bladder instillation. Fill volume, spontaneous voided volume, and PVR were objectively measured; PVR was also calculated.