MISCELLANEOUS The Association of Postvoiding Residual Volume, Uroflowmetry Parameters and Bladder Sensation Hakkı Uzun1*, Maksude Esra Kadıoglu2, Nurgül Orhan Metin2, Görkem Akça1 Purpose: To investigate whether postvoiding residual bladder volume (PVR) and uroflowmetry parameters asso- ciate with bladder sensation in male patients with bladder outlet obstruction (BOO) and to find out the reliable time of these examinations. Materials and Methods: Sixty men with bladder outlet obstruction underwent transabdominal ultrasound in order to measure postvoiding residual volume and uroflowmetry. At the first day, PVR was measured while the patients had mild bladder sensation. Patients emptied their bladder during uroflowmetry. The next day, same patients un- derwent a second uroflowmetry and PVR measurement while the patients had severe bladder sensation. The first and next day PVR and uroflowmetry parameters were compared and their correlation with lower urinary tract symptoms (LUTS) were analysed. Results: The mean age of the subjects was 69.7 ± 8.6 years. PVR measured at the first day while patients had mild bladder sensation was significantly lower than the next day PVR (mean ± SD: 80.79 ± 72.18 vs 158 ± 115.82, P < 0.001) and correlated with LUTS (rs =0.38, P = 0.012). In contrary, uroflowmetry parameters at severe sensation of bladder (mean ± SD: Qmax:13.53 ± 6.32; Qave:5.32 ± 2.31) showed correlation with LUTS (rs = -0.492, P = 0.001). Conclusion: PVR measurement at mild bladder sensation correlates with LUTS and should be performed in the evaluation of male patients with BOO. However, uroflowmetry is advised to be performed when the patient has severe bladder sensation. Keywords: Bladder sensation; Postvoiding residual volume; Bladder outlet obstruction; Uroflowmetry INTRODUCTION Men with lower urinary tract symptoms (LUTS) related to bladder outlet obstruction (BOO) in- cluding bening prostatic hyperplasia is a very prevalent disease constituting a great amount of patients evaluat- ed in urology practice.(1) Uroflowmetry and postvoiding residual urine volume (PVR) measurement are recom- mended for both the initial evaluation and follow-up af- ter medical or surgical treatment of male patients with LUTS.(2) These examinations are simple, non-invasive, widespread and have a prominent role in the manage- ment of the patients.(2-4) Ultrasound is commonly used for the estimation of PVR and easy to perform and highly accurate.(5) In most radiology departments, patients are advised to drink a significant amount of fluid to measure PVR and also to image the urinary tract reliably.(6-8) In guidelines, uroflowmetry is recommended to be carried out with a voided volume of over 150 mL.(2) Consequently, PVR and urine flow rate are usually measured under severe sensation of bladder and this is quite incompatible with real life and does not represent the patient’s daily void- ing practice. It is reported that a residual volume over 100 ml after an increased oral fluid intake may acutely and temporarily decompensate the bladder and might lead to the selection of an inappropriate treatment mo- 1Department of Urology, Recep Tayyip Erdogan University Medical School, Rize, Turkey. 2Department of Radiology, Recep Tayyip Erdogan University Medical School, Rize, Turkey. *Correspondence: Department of Urology, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey. Tel: +90 464 212 30 09. Fax: +90 464 212 30 15. E mail: hakuzun@yahoo.com. Received January 2018 & Accepted August 2018 dality.(8) Therefore, the accurate measurement of PVR and uroflowmetry in accordance to daily voiding prac- tice is of clinical importance. In our clinical practice, some male patients with BOO reported that they voided more troublesome prior to PVR measurement than their daily routine voiding ac- tivity. To the best our knowledge we noticed that in male patients with BOO association of PVR and uro- flowmetry parameters with bladder sensation has not been thoroughly investigated. Therefore, we intended to investigate whether PVR and uroflowmetry param- eters change according to bladder sensation at the first desire or strong desire to void and to find out the relia- ble time of these examinations. MATERIAL AND METHODS Male patients complaining of LUTS related to BOO were included in the study. BOO was assigned accord- ing to the evaluation of urinary symptoms, radiologic and laboratory examinations with the exclusion of other pelvic pathologies. All patients were subjected to a di- agnostic work-up including medical history, and exam- ined for urinary symptoms with International prostate symptom score (IPSS). Physical examination including digital rectal examination was done and serum levels of urea and creatinine were measured. Ultrasonography Urology Journal/Vol 16 No. 4/ July-August 2019/ pp. 403-406. [DOI: http://dx.doi.org/10.22037/uj.v0i0.4368] Vol 16 No 04 July-August 2019 404 and urinalysis were also obtained to exclude other pel- vic disorders. Patients with a diagnosis of prostate or urothelial cancer, urinary tract infection, distal ureteral or bladder stones, urethral stricture, chronic pelvic pain syndrome, neurological disorder and unstable diabetes were not included into the study. In addition, patients on any medication for LUTS or with a history of uri- nary tract surgery or instrumental intervention were excluded. The study was performed at the urology and radiology departments of our university hospital be- tween March and September 2017 and was approved by the Ethical Committee of our university and written informed consent was obtained from all patients. All patients underwent uroflowmetry and transabdomi- nal ultrasound (Logic E9 with XD clear ultrasonograph- ic scanner, General Healthcare, United States, equipped with a 4.5 to 6 -MHz convex probe) for the examina- tion of the urinary tract and measurement of prevoid- ing bladder volume, prostate volume and PVR in the radiology department. Both of the examinations were again carried out at the next day by the same radiologist and nurse. All ultrasonographic measurements includ- ing prevoiding bladder volume and PVR measurements were performed by the same radiologist (M.E.K). Pa- tients were advised to take an increased amount of water orally prior to examinations without limiting the time and hydration rate. The examinations were performed while the patients had first or strong desire to void. We intended to pretend daily routine practice, therefore uri- nary catheterisation was not applied for artificial blad- der filling. At the first day, the ultrasound was carried out while the patients had first desire to void (mild blad- der sensation). Prevoiding bladder volume was meas- ured and the patients were asked to empty their blad- ders during uroflowmetry. Then, the first PVR (PVR1) was measured by the radiologist under ultrasound by using the prolate ellipsoid method based on the formu- la: Volume = length x width x height x 0.52 on two di- mensions.(9) The next day the same patients underwent a second prevoiding and postvoiding residual volume (PVR2) measurement while the patients had strong desire to void (severe bladder sensation). Uroflowme- try was again performed prior to PVR2 measurement. Maximum urine flow rate (Qmax), average flow rate (Qave) and voided volume were recorded. Wilcoxon signed rank test was used to compare the first and next day PVR values and uroflowmetry parameters. Spearman’s correlation rank test was used to determine whether the first and next day PVR was correlated with IPSS total score, prostate volume, prostate specific an- tigen (PSA), age, prevoiding bladder volume and se- rum creatinine levels. In addition, correlation between uroflowmetry parameters and IPSS total score was ana- lysed by the same statistical method. SPPS 23 was used for statistical analyses and P < 0.05 was considered as statistically significant. RESULTS Sixty men with bladder outlet obstruction and a mean age of 69.7 ± 8.6 years were evaluated. Descriptive characteristics of the patients are shown in Table 1. Most of the patients had moderate (15/60) or severe symptoms (41/60). Only 4 patients presented with mild symptoms (IPPS <7). The mean prostate volume and Table 1. Descriptive statistics Minimum Maximum Mean SD Age 53 86 69.7 8.6 IPSS total score 4 35 21.04 8.1 PSA (ng/dL) 0.21 15.95 4.12 3.83 Prostate volume (mL) 14 190 67.8 37.9 Serum Creatinine (mg/dL) 0.71 2.23 1.0 0.3 Testosterone 249.65 1078.08 554.08 192.89 Abbreviations: IPSS, International prostate symptom score; PSA, Prostate specific antigen Abbreviations: PVR1, Postvoiding residual volume measured at first desire to void; PVR2, Postvoiding residual volume measured at strong desire to void; PreV1, Prevoiding bladder volume measured at first desire to void; PreV2, Prevoiding bladder volume measured at strong desire to void; Qmax1, Q maximum measured at first desire to void; Qmax2, Q maximum measured at strong desire to void; Qave1, Q average measured at first desire to void; Qave2, Q average measured at strong desire to void; Vv1, Voided volume at uroflowmetry at first desire to void; Vv2, Voided volume at uroflowmetry at strong desire to void Mean SD Significance (P) PVR1 80.79 72.18 PVR2 158.35 115.82 PVR2 – PVR1 < 0.001 PreV1 203.16 108.18 PreV2 422.33 203.22 PreV2 – PreV1 < 0.001 Qmax1 10.74 5.77 Qmax2 13.53 6.32 Qmax2 – Qmax1 0.021 Qave1 4.03 1.90 Qave2 5.32 2.31 Qave2 – Qave1 0.018 Vv1 162.05 103.28 Vv2 270.40 128.62 Vv2 –Vv1 < 0.001 Table 2. Wilcoxon signed rank test showed statistical significance between measurements at the first desire and strong desire to void. Sensation, residual volume and uroflowmetry-Uzun et al. mean serum PSA was measured 67.8 mg and 4.12 ng/ dL, respectively. Prevoiding bladder volume and postvoiding residual volume at the first desire to void (PVR1, measured at the first day) were significantly found lower than the strong desire to void (PVR2, measured at the next day) (P < 0.001) (Table 2). Furthermore, Qmax and Qave values and voided volume were also significantly lower at the first desire to void in comparison to the strong desire to void (Table 2). While Spearman’s rank correlation coefficient showed correlation between PRV1 and IPSS total score (rs =0.38, P = 0.012), PVR2 was not found correlated (Ta- ble 3). In addition, prevoiding bladder volume at first desire and strong desire to void correlated with residual volume measured at the first and next day, respectively (Table 3). Prostate volume, total PSA, age, and serum creatinine levels were not correlated with residual vol- ume measured either at the first desire or strong desire to void. In contrary, Qmax and Qave values at the first desire to void did not show correlation with total IPSS, but showed significant correlation at the strong desire to void (rs = -0.335, P = 0.28 and rs = -0.492, P = 0.001, respectively) (Table 4). DISCUSSION Although PVR measurement and uroflowmetry are one of the most frequently performed urologic exam- inations worldwide for male patients with LUTS, the optimal time of these examinations in terms of bladder sensation has not been adequately investigated. To the best of our knowledge this is the first study that com- pared the PVR and uroflowmetry parameters according to bladder sensation in male patients with BOO. In our study, we found that patients at the strong desire to void showed higher prevoiding bladder volume and PVR. While PVR2 did not show correlation with LUTS, PVR1 was significantly correlated with LUTS. PVR measurement at mild bladder sensation of voiding (first desire to void) could be more reliable for the accurate diagnosis of BOO. On the other hand, in contrast to PVR findings, Qmax and Qave values did not correlate with LUTS at the first desire to void, but a significant correlation was found with symptoms at the strong de- sire to void. Severe bladder sensation for uroflowmetry could be more acceptable. Male patients with LUTS related to BOO are treated with medications (alpha blockers, antimuscarinics, 5 alpha reductase inhibitors) or surgery.(2) The choice of the treatment is mainly based on symptom severity and voiding examinations. Although there is no con- sensus for the PVR threshold, many urologists suggest that high values are an indication for invasive therapy. (10) Furthermore, large PVR volume has been reported to be associated with hydronephrosis, bladder calculi, nocturia, acute urinary retention and urinary tract in- fections.(11) All these relations show the importance of the accurate values of PVR. In a study by Mochtar et al. only over 300 mL of PVR has been found correlat- ed with a need for an invasive therapy.(12) In our study, prevoiding bladder volume at first and strong desire to void significantly correlated with PVR1 and PVR2, re- spectively. An increase in prevoiding bladder volume caused an increase in PVR which was not correlated with the symptom severity of the patients. We believe that patients should have mild bladder sensation prior to PVR measurement for the accurate treatment modal- ity. Previous studies that investigated the relationship of PVR with BOO might have included patients which PVR was measured under severe bladder sensation. Ac- cording to our results these studies could be better per- formed with patients at mild bladder sensation. Further studies are needed for the re-evaluation of the relation between PVR and BOO. Uroflowmetry is a non-invasive, easily practiced and non-expensive test for the evaluation of patients with BOO.(12) Qmax is found an independent predictor of urodynamic BOO(4) and 10 ml/sec is widely accepted as a threshold. However, similar to PVR, there is also a discrepancy and debate between the uroflowmetry parameters and diagnosis of BOO.(13) It is generally ac- cepted that the voided volume should be over 150 mL for the accuracy of the test.(2) In our study the mean voided volume at the first desire to void was 162.05 mL. However, no correlation was found between IPSS total score and Qmax and Qave values when the pa- Table 3. Correlations between postvoiding residual volume at the first desire and strong desire to void and examined parameters. PVR1 PVR2 rs P rs P IPSS total score 0.380 0.012 0.113 0.396 Serum creatinine -0.003 0.987 -0.008 0.961 PreV1 0.639 0.000 N/A N/A PreV2 N/A N/A 0.709 0.000 PSA 0.114 0.472 -0.088 0.580 Prostate volume 0.221 0.154 0.179 0.250 Age 0.058 0.714 -0.188 0.227 Abbreviations: PVR1, Postvoiding residual volume measured at first desire to void; PVR2, Postvoiding residual volume measured at strong desire to void; PreV1, Prevoiding bladder volume measured at first desire to void; PreV2, Prevoiding bladder volume measured at first desire to void; IPSS, International Prostate Symptom Score; PSA, Prostate specific antigen; rs, Spearman’s correlation coefficient. IPSS total score rs P Qmax1 -0.021 0.913 Qave1 -0.265 0.086 Qmax2 -0.335 0.028 Qave2 -0.492 0.001 Qmax1, Q maximum measured at first desire to void; Qmax2, Q maximum measured at strong desire to void; Qave1, Q average measured at first desire to void; Qave2, Q average measured at strong desire to void; rs, Spearman’s correlation coefficient Table 4. Correlations between Q maximum and Q average at the first and strong desire to void and IPSS. Sensation, residual volume and uroflowmetry-Uzun et al. Miscellaneus 405 Vol 16 No 04 July-August 2019 406 tients voided at the first desire to void. On the other hand, mean voided volume at the strong desire to void was found increased and Qmax and Qave values were correlated with IPSS total score. However, whether the mean voided volume at the first desire to void is over 150 mL and mean Qmax is 10.7 mL/sec, uroflowmetry parameters might not be useful for the evaluation of the patients at mild bladder sensation. In contrast to PVR measurement, we claim that patients should undergo uroflowmetry at strong desire to void for the evalua- tion of relation between Qmax and Qave and urinary symptoms. Alivizatos et al. studied the relation between PVR and increased oral intake of fluids.(8) They included the pa- tients into their study with a PVR over 100 mL meas- ured in the first examination after taking an amount of oral fluid. On a separate day, the same patients were let to drink as their usual days. PVR values significantly found higher at the first measurement but no correlation was found between neither first nor second PVR and IPSS. They claimed that increased oral intake of fluids may suddenly decompensate the bladder and result in high residual volume which do not represent the daily voiding practice. However the authors did not include the patients with PVR less than 100 mL after the first measurement which constitutes a significant amount of patients applied to outpatient clinics. In our study, we did not restrict the patients to take oral fluids prior to ul- trasound examination which is also needed for a better visualisation of the urinary tract. While Alivizatos et al. concluded the negative effect of significant oral intake of fluids prior to PVR measurement, we advise the cli- nicians to measure PVR at the first desire to void which was correlated with LUTS. Additionally, in a group of young men without LUTS 60% of men with a PVR less than 50 ml after mild or moderate bladder sensation had a PVR over 50 mL when they voided after a distend- ed bladder.(11) Although their study was performed on young healthy men which PVR was not needed to be measured in daily urology practice, it emphasized that bladder could fail to empty at very high capacities. The limitations of the study it is performed at only one center and lack of follow up of the patients in order to find out if there is any relation between the findings of our study and response to therapy. CONCLUSIONS In conclusion, PVR measurement at the first desire to void with mild bladder sensation correlates with LUTS and should be performed in the evaluation of the male patients with BOO. However, uroflowmetry is advised to be performed when the patient has strong desire to void. CONFLICTS OF INTEREST No potential conflict of interest relevant to this article was reported. REFERENCES 1. Martin SA, Haren MT, Marshall VR, Lange K, Wittert GA, Members of the Florey Adelaide Male Ageing S. Prevalence and factors associated with uncomplicated storage and voiding lower urinary tract symptoms in community-dwelling Australian men. World J Sensation, residual volume and uroflowmetry-Uzun et al. Urol. 2011;29:179-84. 2. Gratzke C, Bachmann A, Descazeaud A, et al. EAU Guidelines on the Assessment of Non-neurogenic Male Lower Urinary Tract Symptoms including Benign Prostatic Obstruction. Eur Urol. 2015;67:1099-109. 3. Sundaram D, Sankaran PK, Raghunath G, et al. 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