Can Women Accurately Predict Their Voided Volumes?

Importance: Voiding diaries can be onerous, we sought to investigate if some women can predict their voided volumes.

Objectives: The objective of this study is to determine the accuracy of estimated voided volumes and characteristics most predictive of accuracy.

Study design: We prospectively collected data on 101 women undergoing urodynamics for lower urinary tract symptoms and/or prolapse at a tertiary care facility. Data collection included postvoid residual volume, urodynamic diagnosis, flow time and rate, and a 1-time measurement of voided volume into a blinded uroflow. Linear and logistic regression analyses were performed to examine predictors of estimated voided volume (mL).

Results: Mean age was 58.2 years (standard deviation, 12.8 years). The median estimated voided volume and actual voided volume were 240 and 215 mL, respectively. The average percent error was 15% (63% of patients being within a 30% margin of error and 32.7% being within a 20% margin of error). On linear regression analysis, smaller voids of 101 to 200 mL were associated with greater accuracy (R2 = 0.37 P = 0.001) and diagnosis of anxiety was associated with a higher voided volume percent error (P = 0.028). Logistic regression analysis revealed that for every 1 year increase in age, there was a 3% decrease in odds of predicting voiding volume within 30% (odds ratios, 0.97; P = 0.041).

Conclusions: Nearly two-thirds of women estimated their voided volume within 30% of the actual void and one-third of women could predict within 20%. This should be taken into consideration when obtaining patient history, particularly with age and diagnosis of anxiety, and may substantiate use of voiding diaries for accurate measurement in specific populations.