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Year : 2006  |  Volume : 22  |  Issue : 2  |  Page : 125-129

Uroflowmetry, trans rectal ultra sonography and power doppler to develop a less invasive bladder outlet obstruction score in benign prostatic hyperplasia: A prospective analysis

Departments of Urology and Renal Transplantation, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India

Correspondence Address:
Anant Kumar
Department of Urology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-1591.26566

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OBJECTIVE : To evaluate the ability of transrectal power doppler sonography (TRPDS) in combination with conventional grey scale transrectal ultrasonography (TRUS), uroflowmetry and clinical parameters, to predict bladder outlet obstruction (BOO) in benign prostatic hyperplasia (BPH). MATERIALS AND METHODS : Sixty-nine male patients with more than 50 years of age, presenting with lower urinary tract symptoms were evaluated prospectively for BOO secondary to BPH. TRUS was done to estimate prostate volume (PV), transition zone volume (TZV), median lobe projection in the bladder (ML) and bladder wall thickness (BWT). TRPDS was done to measure resistive index (RI) of transition zone vessels. All patients also underwent PFS and depending upon its results, the patients were divided into Group 1 [Abram-Griffiths (AG) number < 40] and Group 2 (AG number >40). Mean values of TRUS and TRPDS parameters and uroflowmetry in the two groups were compared to identify predictive factors for BOO. RESULTS : Demographic profile of Group 1 (n= 42) was similar to that of Group 2 (n= 27). Significant independent factors for prediction of BOO were maximum flow rate, resistive index of transition zone, median lobe projection into the bladder and post void residue. BOO scoring system was developed based on these 4 factors, which showed a specificity of 77.8% and a sensitivity of 85.7%, with an overall predictive value of 82.6%. CONCLUSIONS : Transrectal power doppler ultrasonography (resistive index) in combination with uroflowmetry, median lobe projection in bladder and post void residue measurement can predict BOO with a high specificity and sensitivity.

Keywords: Bladder neck obstruction, urodynamics, resistive index

How to cite this article:
Goyal R, Dubey D, Mandhani A, Srivastava A, Kapoor R, Kumar A. Uroflowmetry, trans rectal ultra sonography and power doppler to develop a less invasive bladder outlet obstruction score in benign prostatic hyperplasia: A prospective analysis. Indian J Urol 2006;22:125-9

How to cite this URL:
Goyal R, Dubey D, Mandhani A, Srivastava A, Kapoor R, Kumar A. Uroflowmetry, trans rectal ultra sonography and power doppler to develop a less invasive bladder outlet obstruction score in benign prostatic hyperplasia: A prospective analysis. Indian J Urol [serial online] 2006 [cited 2023 Mar 28];22:125-9. Available from:

   Introduction Top

Currently, pressure flow study (PFS) is considered a reference standard for the diagnosis of bladder outlet obstruction (BOO). However it is invasive, costly and may be associated with urinary tract infection in a small number of patients. Thus, there is an obvious need for other simpler and less invasive modalities to predict BOO. Transrectal ultrasonography (TRUS) is a useful modality to evaluate prostatic dimensions accurately. Resistive index (RI) of the prostatic tissue calculated on power doppler imaging has shown good correlation with severity of BOO.[1],[2] Many attempts have been made to make a non-invasive model for predicting BOO in BPH patients, but power doppler imaging has never been included as a parameter in few such predictions. This study was performed to evaluate the predictability of BOO with the help of transrectal power doppler sonography (TRPDS) in combination with conventional grey scale TRUS, uroflowmetry and clinical parameters to find a less invasive method for clinical use.

   Materials and Methods Top

From June 2003 to May 2004, 106 male patients of more than 50 years of age with lower urinary tract symptoms (LUTS), were analyzed prospectively. Mean age was 66 years (51-81 years). Chief complaints and AUA symptom score were recorded. Patients with urinary retention, on treatment for BPH with PSA greater than 10 or presence of prostate cancer and previous history of urethral trauma or surgery, were excluded.

Those with PSA values between 4-10 ng/ml underwent TRUS- guided sextant prostatic biopsy. Patients with histologically proven carcinoma prostate were excluded from the study.

Uroflowmetry was done twice for all the patients (Medtronic, Denmark) and more representative flow was taken into consideration. Post void residual urine (PVR) and bladder wall thickness (BWT) were noted in all patients with the help of trans-abdominal sonography. BWT was noted at two different points and mean of two values was noted.

TRUS and TRPDS were done with a 7.5 MHz transrectal probe (B-K Medical, Denmark). To avoid inter-observer variability, the same investigator did all TRUS examinations. Prostate volume (PV) and transition zone volume (TZV) were calculated with the help of in built software, by measuring three dimensions of prostate in transverse and longitudinal sections. Transition zone index (TZI = TZV / PV) was calculated for all patients. The median lobe (ML) projecting into the urinary bladder was measured in sagittal scan. A line was drawn joining the posterior bladder wall and bladder neck and perpendicular distance from the tip of median lobe projection into the bladder was measured [Figure - 1]. Blood flow samplings were taken from the transition zone and spectral waveform analyses were done. Maximum and minimum velocities were marked on the waveform as shown in [Figure - 2]. The in- built software calculated RI. RI was measured at four points in the transition zone and the mean value was selected as representative RI of the prostate. We did not specifically target any vessel, as those were only the peri- urethral vessels.

PFS was performed with Medtronic (Denmark) machine with 'DUET̉ logic' computer software for calculations and graphs. Uroflowmetry was done before starting the study. Urethra calibration was done with 16 F Foleys catheter to empty the bladder. Results of TRPDS were not revealed to the investigator doing the urodynamic study. PFS were performed through a 7 F triple lumen per urethral catheter with the patient in sitting posture, filling being done at the rate of 10-50 ml per minute. Intravesical pressures (Pves) were measured. Rectal pressures were recorded through a 10 F catheter connected to the pressure transducer. Filling was stopped when patient had strong desire to void. Opening pressures and Pdet at maximum flow were recorded and abrams-griffiths (AG) number was calculated (PdetQmax - 2Qmax).

Patients were divided in 2 groups; group 1 with AG number less than or equal to 40 and group 2 with AG number more than 40, to differentiate obstructed patients from non-obstructed ones. Mean values of TRUS parameters, MFR, PVR and AUA score were expressed as mean + standard deviation. Significance of difference between mean values was tested with paired sample t-test when appropriate or a non-parametric Wilcoxon matched pairs signed rank test as necessary. Pearson's coefficient of correlation was used for correlation analysis, as all the parameters were continuous variables. Logistic regression analysis was done to calculate relative power of each statistically significant factor for predicting bladder outlet obstruction. A bladder outlet obstruction score was developed by analyzing the histograms of various parameters. A commercially available computer software package (SPSS 10) was used for statistical analysis.

   Results Top

Sixty-nine patients were eligible for the evaluation as per the inclusion criteria. [Table - 1] shows mean ± SD values of parameters evaluated in all the patients. Forty-two patients were found to have no obstruction (i.e., (AG) number <40, group 1), as compared to 27 having obstructive pattern (AG number > 40, group 2). Mean ± SD values of the parameters in the two groups are shown in [Table - 2]. Mean age was 66.64 ± 7.4 years in Group 1 and 65.3 ±10.6 years in Group 2. Mean values of median lobe projection into the prostate, resistive index of transition zone and post void residue were found to be significantly higher in group 2 ( P <0.01). Maximum free flow was significantly lower in group 2 (6.8 ml/s vs 12.4 ml/s, P <0.0001). As shown in [Table - 2], AUA symptom score, bladder wall thickness, prostate volume, transition zone volume and transition zone index were not found to be significantly different in the two groups. Urodynamic parameters in the two groups are also shown in [Table - 2].

[Table - 3] shows correlation coefficients for different parameters. ML, RI, PVR and MFR were found to have good correlation with AG number. Logistic regression analysis with these 4 parameters versus obstruction or no obstruction showed relative power (exponential B) of each parameter to predict BOO [Table - 4]. Values of RI were represented as percentage, to make the calculations of logistic regression analysis easier. Exp (B) value of 0.787 for maximum flow rate shows that an increase of one unit in flow rate decreases the possibility of bladder outlet obstruction by a factor of 0.787. On the other hand, Exp (B) value of more than 1 for the other three parameters shows that one unit increase in these parameters increases the possibility of BOO by a multiple of respective Exp (B) value. On analysis of histograms of various parameters for both the groups, cutoff points for all the four parameters were assigned [Figure - 3]. MFR of 10 ml/s or more, PVR of 100 ml or less, RI of 0.68 or less and median lobe projection of 4.9 mm or less were assigned a BOO point of 'zero' after analysis of the histograms. [Table - 5] shows the scoring system we developed, based on these cutoff values.

Sensitivity and specificity at the various cut off values of BOO score were determined to select the optimum combination of sensitivity and specificity. Keeping the cut off value of more than 2, BOO could be predicted with 85.7% sensitivity, 77.8% specificity and 82.6% overall predictability [Table - 6]. Therefore a score of more than 2 was the most optimum value for predicting BOO.

   Discussion Top

BPH and BOO are two different entities and severity of BOO is not related with the size of the prostate. However, bladder outlet obstruction correlates well with the intraprostatic pressure, because hyperplastic prostate is like a closed system in which outer capsule closes the inner glandular tissue. As the gland grows, intraprostatic pressure rises. This has been supported by the correlation of urethral pressure profile, with the size of the prostatic adenoma resected at surgery.[3] Along with prostatic urethra, the increased intraprostatic pressure must also compress the blood vessels running in the prostate. Anatomy of the prostate gland can be measured accurately by transrectal ultrasound, but the dynamic compression on prostatic tissue needs doppler imaging. Leventis et al studied normal prostatic vascular anatomy and concluded that power doppler of prostatic tissue demonstrates reproducible flow pattern.[4] They also suggested that power doppler can help to compare vascular anatomy of normal prostate with that of diseased prostate. Use of contrast agents increases the effectiveness of visualizing blood vessels, but these are costly and may not be affordable.

Kojima et al[1] in their preliminary report had noticed a significantly higher RI of prostate in BPH patients with BOO, as compared to healthy individuals (0.72 vs. 0.64, P <0.0001). They also noticed a significant decrease in RI after surgical treatment of BPH patients. The same group of authors measured RI of prostates of 140 patients with LUTS.[2] Urodynamic validation of the results was done for 57 patients. They divided the patients into obstructed and non-obstructed groups with AG number of 40 as cut off (as done in our study). Significant correlation was found between RI and urodynamic parameters. Diagnostic accuracy in their study was 68% with 0.7 as cut off for RI. Tsuru et al have reported their experience with 214 patients of lower urinary tract symptoms.[5] RI of capsular arteries was found to have correlation with international prostatic symptom score and peak flow rate; however they did not validate their findings with PFS. In a recent study, Nose et al[6] used transperineal ultrasonography in 30 patients to measure the velocity flow of urine at the prostatic urethra and sphincteric urethra (doppler urodynamics). They combined this method with intravesical prostatic protrusion (IPP) grading, to diagnose BOO with high sensitivity and specificity. In contrast to our study, their analysis showed poor correlation of MFR and PVR with BOO. The method of calculation of IPP by Nose et al , was similar to the one adopted by us to calculate median lobe protrusion into the bladder. However, we have used RI of transition zone to assess functional component of the BOO. We took mean RI after measuring it at four different points in transition zone, probably from peri-urethral vessels. We feel that TRUS- based evaluation can be more easily and reproduced by a urologist. Moreover, our method does not require separate calculation of individual velocities. It needs to sample a vessel in TZ and to freeze the scan at a position where a typical waveform is visualized. As RI is ratio of two velocities, the exact values of the velocities are not needed to be calculated separately.

Many attempts have been made to formulate a clinical prostate score for BPH. Rosier PF et al[6] developed a clinical prostate score by including prostate size, maximum free flow, post void residue and voided volume. The sensitivity of this score was 80.7%, but it had a low specificity (53%). Kuo HC also developed a clinical prostate score for diagnosis of BOO using parameters of uroflow and prostate measurements.[7] The sensitivity of this score was similar to our study (87.2%), but specificity was again low (60.8%). The BOO score proposed by us has high sensitivity as well as very high specificity, perhaps because the measurement of median lobe projection into the bladder and resistive index of transition zone are the parameters specific for the BOO caused by BPH. The cut off value of RI in our study was 0.69. In our study, significant factors for prediction of BOO were maximum free flow, resistive index of transition zone, median lobe projection into the bladder and post void residue. We found poor correlation of prostate volume, transition zone volume, transition zone index and bladder wall thickness with bladder outlet obstruction.

In our study, the same investigator was involved in all the measurements of TRPDS and was blinded against the PFS findings of the patients; hence the observer bias was kept to the minimum. Advantage of TRPDS combined with clinical parameters in diagnosing BOO is that, it does not involve the risk of UTI. In addition to that, RI is a ratio of two velocities; therefore it is not direction- dependent and can be mastered easily. RI can be used as an objective parameter to compare the efficacy of different drugs on BPH.

   Conclusion Top

Transrectal power doppler sonography (resistive index of transition zone of prostate) in combination with conventional transrectal sonography (median lobe projection), uroflowmetry (maximum flow rate) and post void residue measurements can predict BOO with high specificity and sensitivity. We have tried to develop urodynamically validated non-invasive bladder outlet obstruction score, which has a high predictability for BOO with a specificity of 77.8% and a sensitivity of 85.7%. This scoring system is much simpler to use in routine practice. Further use in a larger group of patients is required for its validation[8].

   References Top

1.Kojima M, Watanabe H, Watanabe M, Okihara K, Naya Y, Ukimura O. Preliminary results of power doppler imaging in benign prostatic hyperplasia. Ultrasound Med Biol 1997;23:1305-9.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Kojima M, Ochiai A, Naya Y, Okihara K, Ukimura O, Miki T. Doppler resistive index in benign prostatic hyperplasia: correlation with ultrasonic appearance of the prostate and infravesical obstruction. Eur Urol 2000;37:436-42.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Kondo A, Narita H, Otani T. Takita T, Kobayashi M, Mitsuya H. Weight estimation of benign prostatic adenoma with urethral pressure profile. Br J Urol 1979;51:290-4.  Back to cited text no. 3    
4.Leventis AK, Shariat SF, Utsunomiya T, Slawin KM. Characteristics of normal prostate vascular anatomy as displayed by power Doppler. Prostate 2001;46:281-8.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Tsuru N, Kurita Y, Masuda H, Suzuki K, Fujita K. Role of doppler ultrasound and resistive index in benign prostatic hypertrophy. Int J Urol 2002;9:427-30.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Nose H, Foo KT, Lim KB, Yokoyama T, Ozava H, Kumon H. Accuracy of two noninvasive methods of diagnosing bladder outlet obstruction using ultrasonography, intravesical prostatic protrusion and velocity flow video urodynamics. Urology 2005;65:493-7.  Back to cited text no. 6    
7.Rosier PF, de Wildt MJ, Wijkstra H, Debruyne FM, de la Rosette JJ. Clinical diagnosis of bladder outlet obstruction in patients with benign prostatic enlargement and lower urinary tract symptoms: Development and urodynamic validation of a clinical prostate score for the objective diagnosis of bladder outlet obstruction. J Urol 1996;155:1649-54.  Back to cited text no. 7    
8.Kuo HC. Clinical prostate score for diagnosis of bladder outlet obstruction by prostate measurements and uroflowmetry. Urology 1999;54:90-6.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]


  [Figure - 1], [Figure - 2], [Figure - 3]

  [Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]

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