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

Area of Science:

• Urology
• Surgical Outcomes
• Patient Monitoring

Background:

• Postoperative urinary retention (POUR) is a common complication.
• Accurate assessment of postvoid residual (PVR) volume is crucial for managing POUR.
• Current methods for PVR assessment include objective measurements (bladder scan, catheterization) and subtraction PVR.

Purpose of the Study:

• To evaluate the accuracy of subtraction PVR compared to objective PVR measurements.
• To determine the reliability of subtraction PVR in identifying postoperative urinary retention (POUR).

Main Methods:

• Secondary analysis of 155 postoperative urogynecologic surgery patients.
• Objective PVR measurement and PVR calculation by subtraction were performed.
• Correlation analysis and assessment of sensitivity, specificity, and predictive values for POUR at different PVR thresholds (100, 150, 200 mL).

Main Results:

• Subtraction PVR and objective PVR measurements showed strong correlation (Pearson r = 0.78, P < 0.001).
• A threshold of 200 mL for POUR yielded the best performance for subtraction PVR.
• However, 48% of women with POUR (≥200 mL by objective measurement) were misclassified as not having retention by subtraction PVR.

Conclusions:

• While subtraction PVR correlates with objective PVR, it significantly underestimates PVR in postoperative patients.
• Objective PVR measurement is superior to subtraction PVR for accurately diagnosing POUR.
• Relying on objective PVR measurement is recommended for postoperative patients to ensure accurate management of urinary retention.