Hypothesis / aims of study
Voiding diaries are a helpful tool in assessing patients with voiding complaints. Despite their utility in diagnosing and monitoring many urologic conditions, patients often find voiding diaries to be inconvenient and cumbersome to complete [1]. Consequently, physicians instead often ask patients to assess their voided volumes subjectively. A recent study found nearly 50% of men with lower urinary tract symptoms could estimate volumes within 20% of their actual voided volume [2]. There are no published studies to date supporting the accuracy of these subjective self-assessments in women. Additionally, women with voiding dysfunction often describe a sensation of incomplete bladder emptying. Currently, no investigations to determine if this sensation correlates to a true elevated PVR have been conducted. Therefore, we aim to determine if women undergoing urodynamics (UDS) can accurately predict their voided volume and post-void residual volume (PVR).
Study design, materials and methods
In this single-center, prospective interim study, an institutional review board-approved questionnaire was administered to female patients undergoing UDS from December 2020 to April 2021. Women were excluded if they were under 18 years of age, pregnant, or had underlying neurological or visual disorders making volume estimation difficult. After obtaining informed consent, patients were asked to predict their pre-void, post-void, and PVR volumes quantitatively.
Patient demographics, medical history, surgical history, and UDS indication were collected. Measured urodynamic parameters included maximum flow rate, voiding time, uroflow morphology, voided volume, and PVR. The urodynamic studies were performed in a standardized and reproducible manner according to Good Urodynamic Practice. Estimated pre-void, post-void, and PVR percent errors were calculated by comparing a patient's estimated voided volume to their actual voided volume.
Descriptive statistics were reported for the sample, as well as urodynamic outcomes. Estimated percent error was calculated for pre-void, post-void, and PVR based on the patients' estimated and actual volumes. All analyses were performed in SAS 9.4 (SAS Institute Inc., Cary, NC).
Results
Patient demographics and characteristics are presented in Table 1. 82 women underwent urodynamics testing with a mean age of 53.8 years (SD: 14.4) and median body mass index (BMI) of 28.1 kg/m2 (IQR: 24.6, 33.0). More than half (56.1%) were post-menopausal and, common comorbidities included hypertension (24.4%) and thyroid disease (18.3%). 10 (9.8%) patients received surgical treatment for their voiding dysfunction before enrolling in the study, with midurethral mesh sling being the most common treatment modality (4 cases (4.9%)). The most prevalent primary indications for urodynamic testing were stress incontinence (25.6%), mixed incontinence (18.3%), and frequency/urgency/OAB (13.4%). Stress incontinence was the most common primary diagnosis (32.9%), followed by sensory overactive bladder/low bladder capacity/bladder oversensitivity (20.7%) and normal study (18.3%).
Table 2 summarizes the voided volumes and PVR outcomes. The median estimated pre-void and post-void volume was 150.0 mL (IQR: 100.0, 250.0) and 137.5 mL (IQR: 75.0, 250.0), respectively, compared to the median actual volume of 103.0 mL (IQR: 54.5, 200.5). The median estimated PVR was 0.0 mL (IQR: 0.0, 25.0), which was lower than the median actual PVR (5.0 mL (IQR: 0.1, 37.0)).
Interpretation of results
Our results found women tended to overestimate their voided volume both before and after void (median percent error: 43.2% and 23.2%, respectively). Only 17.1% of women were able to estimate their voided volume within 20% accuracy before their void, while 28.9% of women were able to do so after their void. Post-void residual was typically underestimated with a median percent error of -20.0%, and 24.7% were able to estimate PVR within a 20% margin of error.