Importance of prostate volume and urinary flow rate in prediction of bladder outlet obstruction in men with symptomatic benign prostatic hyperplasia.

BPH Importance of prostate volume and urinary flow rate in prediction of bladder outlet obstruction in men with symptomatic benign prostatic hyperplasia Darius Trumbeckas1, Daimantas Milonas1, Mindaugas Jievaltas1, Aivaras Jonas Matjosaitis1, Marius Kincius1, Aivaras Grybas1, Vytis Kopustinskas2 1Clinic of Urology, Lithuanian University of Health Sciences, Kaunas, Lithuania 2Centre of Statistics, University of Vytautas Magnus, Kaunas, Lithuania key words prostate volume » urinary flow rate » bladder outlet obstruction » benign prostatic hyperplasia » pressure/flow study Abstract Objectives. To predict bladder outlet obstruction with parameters of non-invasive investigations for patients with symptomatic benign prostatic hyperplasia. Patients and methods. A sample of 122 men with moderate to severe lower urinary tract symptoms suggestive of benign prostatic hyperplasia was selected. Transrectal prostate ultrasound, free flow measurement, and transabdominal ultrasound for residual urine were carried out together with digital rectal examination for all patients. All patients underwent urodynamic pressure/flow test. Two groups of obstructed (91 patient) and equivocal/unobstructed (31 patient) were analyzed. Probabilistic model based on logistic regression was developed for prediction of obstruction. Results. Various parameters were compared in obstructed and non-obstructed/equivocal groups, highlighting important parameters for obstruction. Correlation analysis indicates higher obstruction dependence on average and peak flow rates and lower dependence on total prostate and transition zone volumes, transition zone index. Binary logistic regression model suggests that average flow rate combined with total prostate volume is the best predictor of obstruction (83% of correct predictions; PPV = 92%; NPV = 52%) in the analyzed sample. The analyzed model suggests that peak flow rate could also be almost equally important parameter instead of average flow rate. Conclusions. The study suggests that average/peak flow rate combined with total prostate volume can be used for prediction of obstruction. The developed probabilistic model helps to determine patients who need invasive urodynamic testing for decision on surgical treatment. INTRODUCTION Benign prostatic enlargement (BPE), bladder outlet obstruction (BOO) and lower urinary tract symptoms (LUTS) is the basic triad for clinical diagnosis of benign prostatic hyperplasia (BPH) [1]. BPH is rare in men younger than 40, but is present in up to 50% of men 75 over 60 years of age and nearly 88% by 80 years of age [2, 3]. Macroscopic enlargement of the gland is found in almost half of men who have microscopic BPH. Symptoms caused by BPH and named LUTS, can be categorized as obstructive (voiding) and irritative (storage). Obstructive symptoms are caused by enlargement of the physical mass of the gland (static component) as well as tone of smooth muscle of the prostatic stroma (dynamic component). Irritative symptoms are associated with the bladder dysfunction caused by BOO [4]. It has been estimated that 25% of men in their sixth decade of life have urinary symptoms and objective signs of BOO [2]. However, the evidence for a direct link between BPE, BOO, and LUTS is far from convincing [4, 5]. The aim of surgical treatment for BPH is to relieve or eliminate BOO. Most patients with LUTS and an enlarged prostate will benefit from prostatectomy; however, part of them still experience persistent storage symptoms [4]. Fifteen to 30% of the patients with BPH do not have a favorable outcome after transurethral resection of the prostate (TURP) if symptoms are considered [6]. One of the main causes of unfavorable results is absence of obstruction before surgery. Pressure-flow urodynamic studies remain the most definitive method of objective documenting BOO. It serves as the best instrument to find out if the symptoms are caused by prostatic obstruction or bladder dysfunction [7]. Preoperative investigations with pressure-flow study has been demonstrated that 20-50% of patients with LUTS had no urodynamic evidence of obstruction [7-9]. However suitability of urodynamics in assessing BPH is controversial in terms of invasiveness, cost, time consumption, and, both, reproducibility and variability of results [7]. Therefore these studies still are not routinely recommended in BPH. It has been proven that the diagnosis of BOO cannot be made by symptomatic assessment alone [8]. Size of prostate and postvoid residual (PVR) of urine are important in evaluation of BPH, but not critical for diagnosis of obstruction. It has been confirmed by studies that the best single predictor of BOO is urinary flow rate. Approximately 70% of men with peak flow rate (Qmax) less than 15 ml/s are obstructed [10]. Value of other parameters of free flow is more controversial. Recent studies show that ultrasound estimated prostate weight or prostate transition zone volume can also predict obstruction [11, 12]. Better prediction of obstruction using parameters of noninvasive investigations aimed to improve results of BPH surgery is an important topic for more than two decades, but there is no worldwide-accepted model. Some studies show that predictability of conventional tests alone or in combination for BOO is only 60-70% [13]. The aim of our study was to look for possibly better simple predictors. Central European Journal of Urology 2011/64/2 Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas, Aivaras Jonas Matjosaitis, Marius Kincius, Aivaras Grybas, Vytis Kopustinskas MATERIAL AND METHODS There were 122 men aged 45-85 years with moderate to severe LUTS suggestive for BPH involved in this prospective study during the period from March 2003 to December 2004. Permission for the study was obtained from the Regional Ethics Committee. Informed consent was received from all patients. Only subjects with International Prostate Symptom Score (IPSS) ≥7 and Qmax in range 3-20 ml/s in total voided volume of 120 ml or greater were included. Symptoms were measured according IPSS together with quality of life (QoL) question. All uroflow traces were reviewed by a single investigator for correction of artifacts. Individuals who had undergone previous prostate or lower urinary tract surgery or who had prostate cancer or PSA level exceeding 10 ng/ml were excluded. Carcinoma of the prostate in case of PSA range 4 to 10 ng/ml had to be excluded by prostate biopsy. Patients with bladder stones, urinary tract infection, and suprapubic drainage as well as evidence of neurogenic bladder were excluded from the study. Uroflowmetric free urinary flow measurement (Urodyn 1000, Medtronic) was performed for flow parameters. Prostate size was measured by transrectal ultrasound (Siemens Sonoline SI-250 with probe of 5-7.5 MHz) evaluating total prostate volume (TPV) as well as transition zone volume (TZV). For calculation of prostate volume, the ellipsoid formula (0.52 x width x height x l (...truncated)