Medicina (Kaunas) 2006; 42(1) KLINIKINIAI TYRIMAI

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1 KLINIKINIAI TYRIMAI 15 Influence of catheter on urinary flow during urodynamic pressureflow study in men with symptomatic benign prostatic hyperplasia Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas, Mindaugas Danilevičius, Aivaras Jonas Matjošaitis Clinic of Urology, Kaunas University of Medicine, Lithuania Key words: benign prostatic hyperplasia, maximum flow rate, pressure-flow study. Summary. Value of urodynamic pressure-flow studies in evaluation of bladder outlet obstruction has been recognized. Voiding during these studies is influenced by transurethral catheter, which is used for measurement of vesical pressure. We have investigated the influence of 7 F (2.3 mm) catheter on flow rate during pressure-flow study as a potential cause of misclassification. Patients and methods. Data of free urinary flow and pressure flow from 111 men with symptomatic benign prostatic hyperplasia were analyzed. Inclusion criteria for analysis: age over 45 years, total International Prostate Symptom Score over 8, maximum flow rate in range of 4 20 ml/s, total voided volume of 100 ml or greater. Results. Of all patients, means of maximum free and pressure-flow rate were 9.8 and 9.0 ml/s (p=0.01) with mean voided volume 199 and 212 ml (p=0.03) respectively. Maximum flow rate decreased in 56.8%, increased in 41.4% and was stable in 1.8% of cases. The difference ranged from 8.5 to ml/s ( + is indicated when maximum rate of free flow is higher). In the group of obstructed subjects mean maximum flow rates were respectively 8.8 ml/s and 7.9 ml/s (p=0.01). There was no significant difference in maximum flow rate within the group of unobstructed/ equivocal subjects. More pronounced mean 1.3 ml/s difference in maximum flow rate was observed also in subgroup of patients with prostate volumes over 60 cc (p=0.01). Conclusions. Catheter of 7 F (2.3 mm) generally slightly diminishes maximum flow rate. Overdiagnosis of obstruction is more likely if considering the effect of catheter and vesical pressure. Misclassification of subject is possible in case of mild obstruction so such cases should be interpreted with caution. In the case of big difference in maximum flow rate it is necessary to take into account the free flow. Introduction The value of pressure-flow studies in evaluation of obstruction for patients with benign prostatic hyperplasia has been recognized (1, 2). According to Guidelines of European Association of Urology 2001, these studies are optional and should be considered for patients prior to surgical treatment in the following subgroups: men younger than 50 and older than 80 years of age, in case of post-void residual volume of urine over 300 ml, peak flow rate more than 15 ml/s (probability of bladder outlet obstruction only 7 15% (3)), suspicion of neurogenic bladder dysfunction, after radical pelvic surgery or previous unsuccessful invasive treatment. In other words these studies are reserved for cases when simple uroflowmetry is particularly limited in predicting of obstruction. However, big cross-sectional diameter of transurethral catheter used for measurement of vesical pressure during pressure-flow study is a major cause for unreliable flow pattern. Flow rate is significantly reduced in case of urodynamic catheter of over 10 F (4), but even catheters of smaller cross-sectional diameter can cause diminished flow. The result of pressure-flow study in case of substantially impaired maximum flow rate is not reliable. Big difference between maximum free flow rate and maximum pressure-flow rate possibly indicates the influence of catheter, therefore, results of such study should be interpreted with Correspondence to D. Trumbeckas, Clinic of Urology, Kaunas University of Medicine, Eivenių 2, Kaunas, Lithuania dtrumbec@takas.lt

2 16 Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas et al. caution. There is no strict recommendation what size of catheter should be used. Recently transurethral measuring of vesical pressure as simple and less invasive method is widely used and many investigators use catheter of 5 8 F ( mm) (3, 5 12). Double lumen transurethral catheters are commercially available and used recently for pressure-flow studies. Suprapubic measurement of vesical pressure as more invasive method is rarely used routinely. It is important to consider the difference between maximum free and pressure-flow rates as possible cause of misinterpretation of invasive urodynamic pressure-flow study. We have evaluated the influence of 7 F (2.3 mm) catheter on maximum flow rate during pressure-flow study and compared our results to the published data. Patients and methods One hundred and twenty four men with lower urinary tract symptoms (frequency, urgency, hesitancy, poor urinary stream, incomplete voiding) suggestive of benign prostatic hyperplasia participated in prospective study at the Department of Urology of Kaunas University of Medicine Hospital. Free-flow measurements and symptomatic as well as objective assessment were performed together with subsequent pressure-flow study. Inclusion criteria for recent analysis were: age over 45 year old, International Prostate Symptom Score equal or greater than 8, maximum flow rate in the range of 4 20 ml/s with voided volume at least of 100 ml. According to the inclusion criteria 111 patients were selected. Patients with hematuria, bladder stones, urinary infection and/or suspicion of bladder malignancy were not included. Previous surgery on prostate or bladder was an exclusion criterion. Carcinoma of the prostate was ruled out by routine prostate-specific antigen (PSA) testing and digital rectal examination. Uroflowmetry for evaluation of free-flow was performed (Urodyn 1000, Medtronic) in standard fashion (13) with subsequent cystometry and pressure-flow study (Duet Logic urodynamic system, software version 8.37, Medtronic) (14). Both measurements were performed in standing position. Pressure-flow study was repeated as recommended by International Continence Society Good Urodynamics Practice recommendations (15). All free-flow and pressure-flow recordings were evaluated by visual inspection of the curves. The representative examination with the best maximum flow rate was chosen to quantify the grade of obstruction. Obstruction was evaluated according to Abrams Griffiths (AG) number. In case of AG number of over 40 subjects were identified as obstructed (16) otherwise unobstructed/equivocal (16, 17). Pressure-flow plots were evaluated using linearized passive urethral resistance relation (linpurr) as well and obstructed subjects were categorized into two groups (low-grade and high-grade obstruction, grade III IV and V VI groups according to linpurr) (18). Maximum flow rate and voided volume of free-flow were compared with the same parameters obtained from pressure-flow study. The same type of uroflowmetry device for the recording of pressure urinary flow and free flow was used. Principles of uroflowmetry and pressure-flow study Uroflowmetry (free-flow measurement) was performed in standing position and normal desire to void before examination. Patient was asked to void in usual way. Uroflowmetric traces were reviewed for the artifacts. Voided volume of over 100 ml was considered sufficient for the evaluation of maximum flow rate (19). Pressure-flow study was performed (Fig. 1) according to the International Continence Society recommendations. Close end 7 F double lumen lubricated transurethral catheter was inserted into the bladder for measurement of vesical pressure. Single lumen Nelaton 10 F catheter in the rectum was used for the measurement of abdominal pressure. Bladder was filled with body-warm sterile saline via pump in rate of 30 ml/s. The pressures were measured with external water pressure transducers. Main pressure is detrusor pressure (Pdet). It is calculated by subtraction of abdominal pressure (Pabd) from vesical pressure (Pves), Pdet=Pves Pabd. Voiding with catheter in the urethra (alongside the catheter) was performed in standing position after normal desire to void. The number of obstruction is calculated by computerized system according the formula: detrusor pressure at maximum flow rate (Pdet ) minus maximum flow rate ( ) multiplied by 2 (AG=Pdet 2 ). The grade of obstruction can be evaluated by standard International Continence Society and Shafer (linpurr) nomograms as well. SPSS (Statistical Package for Social Sciences) software 10.0 was used for statistical analysis. Mean, standard deviation, range, and percentiles were calculated. Distribution of the data was checked before comparison of means. Means were compared using nonparametric Wilcoxon matched-pairs signed ranks test in case of nonparametric distribution or t-test for

3 Influence of catheter on urinary flow during urodynamic pressure-flow study in men 17 Fig. 1. Diagnostic set-up for pressure-flow study (14) 1 transurethral catheter for the measurement of vesical pressure, 2 rectal catheter for the measurement of abdominal pressure, 3 uroflowmetry device, 4 pressure transducers, 5 output to the screen of computer. paired samples in case of normal distribution of variables. A p-value bellow 0.05 was considered as statistical significant. Results Of all 111 patients, 79 were obstructed and 32 unobstructed/equivocal according to the pressure-flow study. Characteristics of patients are presented in Table 1. If all patients assumed, mean maximum flow rate was 9.8±3.5 and 9.0±3.4 ml/s for free and pressureflow, respectively. Statistically significant difference of 0.8±3.1 ml/s was found (p=0.012) (Fig. 2). If freeflow compared with pressure-flow, maximum flow rate decreased in 63 (56.8%), increased in 46 (41.4%) and was stable in 2 (1.8%) cases. The difference ranged from 8.5 to ml/s (10 90 percentiles: 3.2 to +4.8) ( + is indicated when maximum of free flow is higher than maximum of pressure flow) (Fig. 3). Mean decrease in maximum flow rate was 2.8±2.2 ml/s (range , percentiles ) and mean increase 2.0±1.7 ml/s (range , Table 1. General characteristics of patients (n=111) Parameter Mean SD Range percentiles Age (years) IPSS Total prostate volume (cc) of free flow (ml/s) of PQ (ml/s) Q ave of free flow (ml/s) Q ave of PQ (ml/s) Voided volume of free flow (ml) Voided volume of PQ (ml) AG number maximum flow rate; Q ave average flow rate; PQ pressure flow; IPSS International Prostate Symptom Score; AG Abrams Griffiths number.

4 18 Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas et al. 20 Mean difference in, ml/s Fig. 2. Mean difference in maximum flow rate ( ) between free and pressure flow was 0.8 ml/s (positive when higher in free flow), n=111. Number of patients Difference in, ml/s Fig. 3. Variation in maximum flow ( ) difference between free and pressure flow (n=111) Positive when of free flow is higher than of pressure flow. percentiles ). Mean voided volumes were 199±90.8 ml and 212±71.8 ml in free and pressureflow, respectively (p=0.029). Average flow rates were 5.1±2.3 and 4.6±1.8 ml/s, respectively, with difference of just 0.5 ml/s (p=0.014) between the groups. Correlation coefficient for maximum free-flow and maximum pressure-flow was 0.6 and for voided volumes 0.5, respectively (p=0.0001). There were 79 urodynamically-obstructed patients with mean AG number of 81±31.5. Mean maximum flow rates within this group were 8.8±2.7 and 8.0±2.7 for free and pressure-flow, respectively (p=0.01). Mean voided volumes were 189±82.2 and 201±67.5 ml, respectively (p=0.07). The group of unobstructed/equivocal patients comprised 32 subjects with mean AG number of 27±8.8. Mean maximum rates of free and pressure-flow within the group were 12.3±4.2 and 11.6±3.5 ml/s, (p=0.432) with voided volumes of 229±106.7 ml and 242±73.3 ml, respectively (p=0.274). Data according to the groups with different obstruction are presented in Table 2. Subgroups with the different prostate volumes were analyzed. Statistically significant difference in mean maximum flow rates was found only in the case of bigger prostates and this difference was slightly greater in the case of prostate volume of over 60 cc (Table 3). There were no clear correlations between the difference of maximum flow rate and grade of obstruction (Abrams Griffiths number) as well as total prostate volume. Discussion Uroflowmetry is the recording of the free urinary flow rate throughout the course of micturition. It should be regarded as the basic noninvasive clinical urodynamic test. Uroflowmetry is an excellent test to discriminate between normal and impaired micturition (13). However, if a differential diagnosis is required between infravesical obstruction and/or impaired detrusor contractility, the additional information on the detrusor pressure signal is obligatory. This can be achieved only by invasive pressure-flow study. Free flow rates only determine the probability of obstruction; whereas pressure-flow studies can categorize the degree of obstruction and identify patients in whom

5 Influence of catheter on urinary flow during urodynamic pressure-flow study in men 19 Table 2. Differences between maximum flow rates in obstructed and unobstructed/equivocal patients free PQ Difference Obstruction category (ml/s) (ml/s) (ml/s) p-value mean SD mean SD mean SD Obstructed patients (n=79) High-grade obstruction (n=26) Low-grade obstruction (n=53) Unobstructed/equivocal patients (n=32) NS All patients (n=111) maximum flow rate; PQ pressure flow; NS not significant difference. Total prostate volume, cc Table 3. Differences between maximum free and pressure-flow rates in the groups divided according to the prostate volume free (ml/s) PQ (ml/s) Difference (ml/s) mean SD mean SD mean SD (n=42) NS (n=20) NS (n=25) NS (n=68) NS (n=51) NS (n=26) NS >30 (n=83) NS >40 (n=61) >50 (n=45) >60 (n=35) <20 (n=8) NS maximum flow rate; PQ pressure flow; NS not significant difference. p-value low flow rate may be due to low-pressure detrusor contraction (20). It is possible to predict the likelihood of obstruction by uroflowmetry alone. Maximum flow rate of <10 ml/s indicates nearly 90% probability of obstruction, whereas maximum flow rate in range of ml/s correctly predicts the obstruction only around in 67% (20) or even less of cases (3). So obstruction can be diagnosed accurately only with a pressure-flow study (20) simultaneous recording of bladder pressure and urinary flow rate. Though pressure-flow studies are the only reliable method for diagnosis of obstruction, their results can be influenced by some factors. Transurethral catheter, which is used for measurement of vesical pressure during voiding, is the main cause of biased flow. Voiding with catheter in the urethra is not physiologic. Some controversies exist concerning the influence of catheters on flow rate and impact on the accuracy of diagnosis. One can see that the free urinary flow is different from the flow during pressure-flow study but the difference is variable. Some authors state that the influence of a 6 F (2.0 mm) catheter in benign prostatic enlargement is moderate (14), others that even a 8 F (2.7 mm) catheter does not appear to have a significant obstructive effect in the urethra (12). Transurethral catheters of over 10 F (3.3 mm) should be avoided (21) because of significant obstructive effect (14). Generally, it is accepted that catheters of over 8 F (2.7 mm) should not be used for pressure-flow studies and investigators usually recommend a catheter as thin as possible. From the other hand, it is more difficult to insert very thin and soft catheter into the bladder and such catheters are more tended to be voided out

6 20 Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas et al. during pressure-flow study. Though it seems that obstructive effect of any transurethral catheter is inevitable and flow rate should be diminished, really it happens not always. Recently transurethral catheters are widely used for pressureflow studies, because this way is much simple for routine practice. Our data show that the influence of 7 F catheters on maximum flow rate generally is not great and the mean decrease in maximum flow rate is around 1 ml/s if maximum free urinary flow and maximum flow with catheter compared. Not only flow rate is important when pressure-flow studies are evaluated. Vesical and detrusor pressures usually are elevated during pressure-flow study. As it has been shown by H. C. Klingler et al. (22) detrusor pressure at maximum flow in case of removal of 5 F (1.67 mm) and 10 F (3.3 mm) urethral catheter used for pressure-flow study decreased in 9.9% and 18.8%, respectively. The authors also observed parallel increase of maximum flow rate in 21.1% and 55.7%. The above-mentioned can cause misclassification of patients. Data of P. Zhang show that 7 F catheter diminished maximum flow rate in average of 2.2 ml/s compare to free-flow (11). Our results show even lesser difference. Flow rate during pressure-flow study in some cases can be also increased and this can be explained by elasticity, adaptation of urethra as well as irritative effect of catheter. So obstruction caused by crosssectional diameter of the catheter is important but not the only thing. Discomfort and pain during the study also play an important role. If consider results of investigations, misclassification with over diagnosis of obstruction is more likely, especially when AG number is close to above 40 (grade 3 obstruction according linpurr). Effect of catheter in the groups of obstructed patients and subjects with prostate volumes over 60 cc can be more pronounced. However, these findings can be clinically relevant only when mild obstruction diagnosed (misclassification of subject is more likely). If great difference between free flow and pressureflow is found pressure-flow study should be interpreted with caution and free flow rate and detrusor pressure should be taken into consideration when evaluating the degree of bladder outlet obstruction (11), especially in close to border range. Conclusions Catheter of 7 F (2.3 mm) generally slightly diminishes maximum flow rate. Overdiagnosis of obstruction is more likely if considering the effect of catheter and vesical pressure. Misclassification of subject is possible in case of mild obstruction so such cases should be interpreted with caution. In the case of big difference in maximum flow rate it is necessary to take into account the free flow. Acknowledgements We thank dr. Vytis Kopustinskas for his help with statistics. Kateterio įtaka šlapimo tėkmei urodinaminio tyrimo metu vyrams, sergantiems simptomine gerybine priešinės liaukos hiperplazija Darius Trumbeckas, Daimantas Milonas, Mindaugas Jievaltas, Mindaugas Danilevičius, Aivaras Jonas Matjošaitis Kauno medicinos universiteto Urologijos klinika Raktažodžiai: gerybinė priešinės liaukos hiperplazija, maksimalus šlapimo debitas, spaudimo ir tėkmės tyrimas. Santrauka. Urodinaminio spaudimo ir tėkmės tyrimo metu matuojamas spaudimas šlapimo pūslėje ir kartu nustatomas šlapimo debitas tai tiksliausias šlapimo pūslės obstrukciją rodantis tyrimas, tačiau toks šlapinimasis ne visai natūralus, nes esama kateterio uretroje. Atlikta analizė ir tirta 2,3 mm diametro 7 F kateterio įtaka šlapimo tėkmei. Tai svarbu vertinant urodinaminio tyrimo rezultatus. Metodai. Išanalizuota 111 vyrų, atitikusių įtraukimo į tyrimą kriterijus (amžius vyresni nei 45 metų, vidutiniai ir ryškūs simptomai, maksimalus šlapimo debitas 4 20 ml/s, šlapimo tūris per 100 ml), laisvo bei spaudimo ir tėkmės tyrimo metu nustatyto maksimalaus šlapimo debito skirtumai. Laisvos šlapimo tėkmės parametrai: maksimalus debitas ir šlapimo tūris palyginti su atitinkamais urodinaminio tyrimo metu nustatytais parametrais.

7 Influence of catheter on urinary flow during urodynamic pressure-flow study in men 21 Rezultatai. Maksimalaus šlapimo debito vidurkis 9,8 ir 9,0 ml/s (p=0,01), šlapimo tūris 199 ml ir 212 ml (p=0,03) šlapinantis laisvai ir su kateteriu. Maksimalus debitas sumažėjo 56,8 proc., padidėjo 41,4 proc., nepakito 1,8 proc. tiriamųjų. Skirtumas svyravo nuo 8,5 iki +10,2 ml/s ( + nurodytas, kai, šlapinantis laisvai, debitas didesnis nei šlapinantis su kateteriu uretroje). Pacientų, kuriems nustatyta obstrukcija, grupėje maksimalaus šlapimo debito vidurkis buvo atitinkamai 8,8 ml/s ir 7,9 ml/s (p=0,01). Pacientams, kuriems nerasta obstrukcijos, šlapimo debito reikšmingo skirtumo nenustatyta (p=0,4). Kiek didesnis nei 1,3 ml/s maksimalaus debito skirtumas nustatytas tiems tiriamiesiems, kurių priešinės liaukos dydis viršijo 60 cm 3 (p=0,01). Išvados. 7 F (2,3 mm) kateteris palyginti nedaug sumažina šlapimo debitą (vidutinis skirtumas, lyginant su laisva tėkme, apie 1 ml/s). Kadangi, esant kateteriui, kiek padidėja ir spaudimas šlapimo pūslėje, galima obstrukcijos hiperdiagnostika. Tai svarbu įvertinti, jei urodinaminio tyrimo metu nustatoma nedidelė arba ribinė obstrukcija, nes šiuo atveju labiausiai tikėtina neteisinga obstrukcijos diagnozė. Esant dideliam skirtumui, visada būtina atsižvelgti į laisvos tėkmės debitą. Adresas susirašinėti: D. Trumbeckas, KMU Urologijos klinika, Eivenių 2, Kaunas El. paštas: dtrumbec@takas.lt References 1. Abrams P. In support of pressure-flow studies for evaluating men with lower urinary tract symptoms. Urology 1994;44: Te AE, Kaplan S. Urodynamics and benign prostatic hyperplasia. In: Kirby RS, McConnell JD, Fitzpatrick JM, Roehrborn CG, Boyle P, editors. Textbook of benign prostatic hyperplasia. Oxford. Isis Medical Media, LTD.; p Chaple CR, MacDiarmid S. Chapter 3: Urodynamic techniques. In: Chaple CR, MacDiarmid S, editors. Urodynamics. Made easy. 2nd ed. London: WB Saunders; p Schafer W. Urodynamics in benign prostatic hyperplasia (BPH). Arch Ital Urol Androl 1993;65: Rodrigues P, Lucon A, Freire G, Arap S. Urodynamic pressureflow studies can predict the clinical outcome after transurethral prostatic resection. J Urol 2001;165: Walker RM, Romano G, Davies A, Theodorou N, Springall R, Carter S. Pressure-flow study data in a group of asymptomatic male control patients 45 years old or older. J Urol 2001; 165: Gotoh M, Yoshikawa Y, Kondo A, Kondo A, Ono Y, Ohshima S. Prognostic value of pressure-flow study in surgical treatment of benign prostatic obstruction. World J Urol 1999;17: de Lima ML, Netto NRJ. Urodynamic studies in the surgical treatment of benign prostatic hyperplasia. Int Braz J Urol 2003;29: Porru D, Jallous H, Cavalli V, Sallusto F, Rovereto B. Prognostic value of a combination of IPSS, flow rate and residual urine volume compared to pressure-flow studies in the preoperative evaluation of symptomatic BPH. Eur Urol 2002;41: Steele GS, Sullivan M, Sleep D, Yalla S. Combination of symptom score, flow rate and prostate volume for predicting bladder outflow obstruction in men with lower urinary tract symptoms. J Urol 2000;164: Zhang P, Wu Z, Gao J. Impact of catheter on uroflow rate in pressure-flow study. Chin Med J (Engl) 2004;117: Reynard JM, Lim C, Swami S, Abrams P. The obstructive effect of a urethral catheter. J Urol 1996;155: Rollema HJ. Uroflowmetry. In: Siroky MB, Krane RJ, editors. Clinical neurourology. 2nd edition. Boston: Little Brown and Company; p Klarskov P, Mortensen S. URODYN. Urodynamics introduction to clinical application. Copenhagen; p Sullivan J, Lewis P, Howell S, Williams T, Shepherd A, Abrams P. Quality control in urodynamics: a review of urodynamic traces from one centre. BJU Int 2003;91: Lim CS, Abrams P. The Abrams-Griffiths nomogram. World J Urol 1995;13: Madersbacher S, Klingler H, Djavan B, Stulnig T, Schatzl G, Schmidbauer C, et al. Is obstruction predictable by clinical evaluation in patients with lower urinary tract symptoms? Br J Urol 1997;80: Schafer W. Analysis of bladder-outlet function with the linearized passive urethral resistance relation, linpurr, and a disease-specific approach for grading obstruction: from complex to simple. World J Urol 1995;13: Hofner K, Kramer G, Tan H, Grunewald V, Jonas U. Advances in urodynamics. Eur Urol Update Series 1993;2: de la Rosette JJ, Alivizatos G, Madersbacher S, Perachino M, Thomas D, Desgrandchamps F, et al. EAU Guidelines on benign prostatic hyperplasia (BPH). Eur Urol 2001;40(3): Klausner AP, Galea J, Vapnek J. Effect of catheter size on urodynamic assessment of bladder outlet obstruction. Urology 2002;60: Klingler HC, Madersbacher S, Schmidbauer C. Impact of different sized catheters on pressure-flow studies in patients with benign prostatic hyperplasia. Neurourol Urodyn 1996; 15: Received 19 May 2005, accepted 8 December 2005 Straipsnis gautas , priimtas