Uroflowmetry is a simple noninvasive test to assess lower urinary tract function, by measuring the flow of urine over time.  The results of this test are useful in predicting bladder outflow obstruction and assessing the need for more advanced urodynamic testing. Uroflowmetry is an office based test requiring patients to arrive with a full bladder and urinate in an unfamiliar  setting. These issues are clear limitations of its utility. Previously an acoustic uroflow using sound analysis captured on a smartphone was reported as an accurate surrogate for standard office based uroflowmetry. The goal of this study was to validate and confirm the accuracy of uroflow using sound analysis captured on a smart phone when compared to standard uroflowmetry.

With the approval of an institutional review board, male patients ages 18-80 were recruited. Using the recorded sound during urination into a standard office based Gyrus ACMI MMS flowmaster, the results were compared. Male subjects were recorded in standing position. The urine flow rate is calculated as the voiding sound was recorded and processed. Voided volume can be obtained by integrating the calculated flow rate. Cases with voided volume <20mL or having recording problems were excluded. Pearson’s correlation coefficient (PCC, r) was used to compare the maximal flow rate (Qmax), average flow rate (Qavg), and voided volume estimated by the standard uroflowmetry with those calculated by acoustic recording.

A total of 50 male patients were screened. 29 patients were analyzed. Exclusion of 21 patients was required for reasons of inadequate flow or volume. Patients were also excluded for an inability to urinate (6) or, interfering background noise or loss of data (12). Flow patterns recorded by acoustic uroflowmetry and conventional uroflowmetry showed a good visual correlation (Fig 1). For male patients the average Qmax, Qavg and voided volumes were 10.4 mL/s, 4.5ml/s and 143ml respectively using sound based analysis. Standard uroflowmetry results for average Qmax, Qavg and voided volume were 10.2 ml/sec, 4.8 ml/sec and 139.1 ml, respectively.  An excellent correlation was observed between the two different methods for Qmax (r=0.94), Qavg (r=0.98)and voided volume (r=0.98). 

Figure 1. Examples of flow pattern recorded by the standard uroflowmetry (line) and acoustic uroflowmetry (dots) using voiding sound record after processing.

In 2018, Young Ju L et al, reported in an abstract at ICS on a novel mobile based acoustic uroflowmetry [1].  The results reported showed an excellent correlation between acoustic and standard uroflowmetry, with regards to maximum and average flow rates as well as voided volumes.  Our validation study, which examined male patients, confirms the accuracy of this acoustic method of measuring uroflowmetry in comparison to standard uroflowmetry with a high correlation noted with regards to maximum and average flow rates as well as voided volume. 
This easy to use mobile acoustic uroflowmetry can be used to check and monitor the urinary flow rate and volume in patients in daily, natural settings. It can also offer longitudinal trends of urodynamic parameters in a quantitative manner, which will be useful for healthcare providers and payers who need to pre-screen and monitor lower urinary tract symptoms. The possibility that this data may be collected remotely outside the office setting will be valuable as healthcare trends to remote care. The smartphone app additionally uses an automatic voiding diary for daily usage which will be valuable in monitoring patients response to therapy.  Time to void and voided volume can be calculated and filled by predicted urine flow from recording each voiding event, and automatically consolidated for each day. This quantitative and ease-of-use app might improve shortcomings of current voiding diary such as incomplete voiding diaries with missing values and low compliance. Limitations include the interference of results with significant background noise. Additionally, male patients who void while sitting were not accessed.

This validation study confirms the accuracy of a sound based acoustic uroflow in comparison to standard office based uroflow to evaluate lower urinary tract symptoms in male patients. Further studies on predictive values in a true remote setting will be required to confirm the utility of this test.

Young Ju L et al, A Novel Mobile Acoustic Uroflowmetry: Comparison of Uroflowmetry and Mobile Acoustic Uroflowmetry. ICS 2018, Session 9, Abstract 208.