A novel algorithm for the non-invasive detection of bladder outlet obstruction in men with lower urinary tract symptoms

Fawzy Farag; Mohamed Elbadry; Mohammed Saber; Abdelbasset A Badawy; John Heesakkers

doi:10.1016/j.aju.2017.01.002

A novel algorithm for the non-invasive detection of bladder outlet obstruction in men with lower urinary tract symptoms

Arab J Urol. 2017 Mar 6;15(2):153-158. doi: 10.1016/j.aju.2017.01.002. eCollection 2017 Jun.

Authors

Fawzy Farag¹, Mohamed Elbadry², Mohammed Saber¹, Abdelbasset A Badawy¹, John Heesakkers³

Affiliations

¹ Department of Urology, Sohag University Hospital, Sohag, Egypt.
² Department of Urology, Minia University Hospital, Minia, Egypt.
³ Department of Urology, Radboud University Nijmegen Medical Centre, The Netherlands.

Abstract

Objective: To determine the ability of bladder wall thickness (BWT) in combination with non-invasive variables to distinguish patients with bladder outlet obstruction (BOO).

Patients and methods: Patients completed the International Prostate Symptom Score (IPSS) questionnaire and prostate size was measured by transrectal ultrasonography (US). Pressure-flow studies were performed to determine the urodynamic diagnosis. BWT was measured at 250-mL bladder filling using transabdominal US. Recursive partition analysis (RPA) recursively partitions data for relating independent variable(s) to a dependent variable creating a tree of partitions. It finds a set of cuts of the dependent variable(s) that best predict the independent variable, by searching all possible cuts until the desired fit is reached. RPA was used to test the ability of the combined data of BWT, maximum urinary flow rate (Q_max), post-void residual urine volume (PVR), IPSS, and prostate size to predict BOO.

Results: In all, 72 patients were included in the final analysis. The median BWT, voided volumes, PVR, mean Q_max, and IPSS were significantly higher in patients who had an Abrams/Griffiths (A/G) number of >40 (55 patients) compared to those with an A/G number of ≤40 (17 patients). RPA revealed that the combination of BWT and Q_max gave a correct classification in 61 of the 72 patients (85%), with 92% sensitivity and 65% specificity, 87% positive predictive value, and 76% negative predictive value (NPV) for BOO (area under the curve 0.85). The positive diagnostic likelihood ratio of this reclassification fit was 2.6.

Conclusions: It was possible to combine BWT with Q_max to create a new algorithm that could be used as a screening tool for BOO in men with lower urinary tract symptoms.

Keywords: AG, Abrams/Griffiths; BWT, bladder wall thickness; Bladder wall thickness; DO, detrusor overactivity; DWT, detrusor wall thickness; Diagnosis; MCC, maximum cystometric capacity; NPV, negative predictive value; PPV, positive predictive value; PVR, post-void residual urine volume; Pves, vesical pressure; Qmax, maximum urinary flow rate; Urinary bladder neck obstruction; Urinary flowmetry; Urodynamics.