Neurourology and Urodynamics 26:842–846 (2007)

Role of UPP in Evaluating Bladder Outlet ObstructionDue to Benign Prostatic Enlargement

Qiang Fang, Bo Song,* Weibing Li, Gensheng Lu, Xiyu Jin, Xuwei Zhang, and Ruhui FanCenter of Urology of PLA, Southwest Hospital, The Third Military Medical University, Chongqing, China

Aims: To study the role of UPP in assessing bladder outlet obstruction (BOO) due to benign prostatic enlargement (BPE). Materialsand Methods: Urodynamic results from 1281 elderly men with Lower urinary tract symptoms (LUTS) obtained from September 1999through July 2005 were retrospectively analyzed. Independent sample t-test or Wilcoxon signed-rank test was used to compare theparameters of different groups according to PFS. Chi-square test was used to compare the percentage of urethral pressure profile(UPP) types between different groups. ROC curve was used to study the practical value of UPP parameters in diagnosing BOO.Results: According to PFS, patients were divided into three groups: Obstructed, equivocal obstructed and unobstructed. There wassignificant difference between the unobstructed and obstructed group in the age of patients, bladder capacity, residual volume,voided volume, voided time, prostatic plateau area (PPA), prostatic length, functional profile length, pressure of bladder neck, andpressure of seminal colliculus, but not in maximum urethral closure pressure. All UPP parameters correlated significantly to thediagnosis of bladder outlet obstruction due to BPE. The largest area under the ROC curve was that of PPA. Conclusions: Our resultsindicate that PPA on UPP is useful in assessing the grade of obstruction due to BPE when PFS fails, a finding still to be evaluated byprospective studies. Neurourol. Urodynam. 26:842–846, 2007. � 2007 Wiley-Liss, Inc.

Key words: diagnosis; lower urinary tract symptom; men; pressure flow study; urethral pressure profile; urodynamics

INTRODUCTION

Lower urinary tract symptoms (LUTS) are common amongelderly men. The majority of these patients have symptomscaused by benign prostatic obstruction (BPO), whereas asmany as one third of them have other causes of LUTS, such asdetrusor instability or detrusor underactivity.1 Urodynamicstudies, including pressure-flow analysis, are considered thegold standard in diagnosing bladder outlet obstruction (BOO).2

But in clinical practice, many patients cannot perform apressure-flow study (PFS). Only 85% of women gave a goodquality PFS,3 while the achievement ratio in men was evenlower than that. In our laboratory about 35% of men cannotcomplete PFS. So how to evaluate the obstructive degree ofthese people is still a problem.

Urethral pressure profile (UPP) is used to assess urethralclosure and voiding function. Parameters of the UPP reflect thestatic urethral function. Can we use it to evaluate the urethralresistance and the grade of BOO during voiding? Is there somerelationship between the UPP parameters and the grade ofBOO? These questions are to be answered. Therefore, the aimof our study was to compare UPP and PFS results in elderlymen with LUTS and determine whether it helps to diagnoseBOO.

MATERIALS AND METHODS

We carried out urodynamic tests on 2745 men with LUTSdue to benign prostatic enlargement (BPE). PFS was performedby 1756 men and 475 were excluded because of invalid UPPresults according to the exclusive criteria below. Thus theresults from 1281 patients were eligible for this study.

Exclusive criteria: BPE patients with nervous and endocrinesystem disease or clinical evidence of other lower urinary tractdiseases; history of surgery or present medication.

The PFS and UPP were performed using a standardizedurodynamic technique with Dantec urodynamic DUET MULTI-P unit (Denmark). The methods, definitions, and units con-

form to the standards proposed by the InternationalContinence Society (ICS).4–6 Briefly, an 8-F double-lumenurethral catheter was used to withdraw residual urine. A12-F urodynamic balloon catheter was inserted into therectum for recording abdominal pressure. The pressuretransducers, zeroed to atmospheric pressure, were leveled tothe upper edge of the symphysis and connected to thepressure lines. During cystometry, the bladder was filled with1/5000 furacilin solution at a filling rate of 50 ml/min at roomtemperature. Filling was stopped when the patient expresseda strong urge to void. Micturition in a standing positionwas allowed; during micturition, flow and intravesical andabdominal pressures were recorded. Flow was measured usinga rotating disk flowmeter. All data were digitally stored andanalyzed with an urodynamic analysis program. We used theICS standard6 to assign the obstruction status for this study.After voiding, the urodynamic catheter was then advancedinto the bladder and the bladder capacity was adjusted to100 ml. The abdominal pressure was measured using a rectalcatheter. Transducers were zeroed to atmospheric pressure.UPP was performed by perfusion at 2 ml/min while thecatheter was manually withdrawn at 1 mm/sec.7,8

Since there has not been a diagram of a male UPP (static)recommended by the I.C.S., UPP parameters are definedaccording to Abrams et al.9 and our study results. Thepressures of bladder neck (P1) and seminal colliculus (P2)were marked and recorded artificially. P1: Pressure of the first

No conflict of interest reported by the author(s).This paper was accepted under the leadership of Jerry Blaivas.*Correspondence to: Bo Song, Center of Urology of PLA, Southwest Hospital, TheThird Military Medical University, Chongqing 400038, China.E-mail: songbo_mr@vip.sina.com.cnReceived 1 September 2005; Accepted 2 January 2006Published online 12 June 2007 in Wiley InterScience(www.interscience.wiley.com)DOI 10.1002/nau.20227

� 2007 Wiley-Liss, Inc.

peak from the profile beginning to the maximum urethralpressure on the UPP. P2: Pressure of the point that increasingquickly to MUCP on the UPP. Classification criteria of UPPshape is as follow. Saddle-shaped P1-P2 � 5 cmH2O; ladder-shaped: |P1–P2| < 5 cmH2O; Slope-shaped: P2-P1 � 5 cmH2O.Parameter definition of the three kind of UPP showed inFigure 1.

Means and standard deviations were calculated for quanti-tative variables. After testing for normality, group compar-isons were performed using the independent sample t test orWilcoxon signed-rank test. The chi-square test was used tocompare the percentage of UPP types between differentgroups. The receiver operating characteristic (ROC) curve wasused to evaluate the practical value of UPP parameters indiagnosing BOO. A P-value less than 0.05 was consideredstatistically significant. All tests were two sided. The anal-yses were performed using SPSS (version 10.0, SPSS Inc.,Chicago, IL).

RESULTS

The mean age of patients was 67 (49–82) years old. Accordingto PFS, they were divided into three groups: Unobstructed (n ¼168), equivocal obstructed (n ¼ 287) and obstructed (n ¼ 826).

There is no need to compare all pressure and flow rateparameters between the three groups because those para-meters themselves were used to determine the obstructivestatus. The mean age and mean residual volume weresignificantly higher in the patients of the obstructed groupthan those of the other two groups (P< 0.01) Mean voidingtime was significantly longer for patients in the obstructed

and equivocal obstructed groups than those in the unob-structed group (P< 0.01). Mean bladder capacity and meanvoided volume were significantly lower in the obstructedgroup than the unobstructed group (P< 0.01) (see Table I).

According to our classification criteria, there are mainlythree kinds of male UPP patterns: Saddle shaped, laddershaped, and slope shaped (see Fig. 2). There was no significantdifference in the percentage of each pattern between theunobstructed and equivocal obstructed groups. The percen-tage of the saddle-shaped pattern was obviously higher inthe obstructed group than other two groups (P< 0.01) (seeTable III).

As for the ROC curves of UPP parameters in diagnosing BOO,each UPP parameter was found to correlate to the diagnosis ofbladder outflow obstruction caused by BPE (P< 0.01). The largestarea under the ROC curve was that of PPA (see Fig. 3).

In comparison with PFS results, when PPA �2208.50mm cmH2O was set as BOO standard, the specificity was100%, but the sensitivity was only 33.2%, while when CA�1439.50 mm cmH2O was set as BOO standard, the sensitivitywas 95.2% and the specificity was 99.6%. CA distribution ofdifferent groups is shown in Figure 4.

DISCUSSION

Micturition is achieved by a rise in intravesical pressureuntil the bladder is empty, which is preceded by relaxation ofthe pelvic floor muscles and the urethral sphincteric area.Normally, the proximal urethra at the bladder outlet,comprising the bladder neck, the prostatic urethra and thesphincteric area, is relaxed during micturition. The urethral

Neurourology and Urodynamics DOI 10.1002/nau

Fig. 1. Definitions of parameters of different UPP patterns. A: Saddle-shaped. B: Ladder-shaped. C: Slope-shaped.

TABLE I. Mean Ages and PFS Parameters

Unobstructed(n¼ 168 M� SD)

Equivocal obstructed(n¼ 287 M� SD)

Obstructed(n¼ 826 M� SD)

Total(n¼ 1281 M� SD)

Patient age (y) 57.05 � 4.57 63.56 � 8.30*,** 70.41 � 5.78* 67.13 � 7.92

BC (ml) 353.49 � 26.51 320.46 � 63.15*,** 258.72 � 67.01* 284.95 � 72.25

Residual volume (ml) 0.74 � 3.05 6.95 � 12.41 25.51 � 33.16* 18.10 � 29.11

Voided time (sec) 43.43 � 7.00 54.42 � 19.59* 55.38 � 22.87* 53.60 � 21.10

Voided volume (ml) 288.31 � 36.42 209.96 � 84.63 156.68 � 87.82* 185.86 � 93.82

QmaxpQ (ml/sec) 12.93 � 1.87 8.01 � 2.61 6.48 � 2.76 7.66 � 3.38

QavepQ (ml/sec) 6.76 � 0.99 3.98 � 1.36 3.01 � 1.41 3.71 � 1.84

PdetQmax (ml/sec) 33.46 � 4.03 47.97 � 7.42 77.37 � 15.09 65.04 � 21.34

*P< 0.01 versus unobstructed.

**P< 0.01 versus obstructed.

Role of UPP in Evaluating BOO 843

resistance to flow is accordingly very low and the drivingforce, that is, the bladder wall smooth muscle, should exhibitlow pressure for any flow rate. Urethral resistance is definedby the inherent mechanical and morphological properties ofthe proximal urethral wall called the flow-controlling zone.10

During micturition, the bladder outlet or the flow-controllingzone can be obstructive as a result of neurological over-activity or an abnormal anatomical structure such as strictureor more frequently enlargement of the prostate. Obstruction,being a physical concept, implies that urethral resistance toflow is abnormally elevated. Intravesical pressure duringmicturition has been shown to be directly related to urethralresistance.11,12 As urethral resistance increases, flow ratedeclines and higher intravesical pressures are measured. Sinceurethral resistance affects intravesical pressure and flow rate,a direct measurement of this parameter would be desirable inthe diagnostic procedure. However, it is practically difficult.Therefore, standard urodynamic studies were developed basedon indirect methods. Urethral resistance is represented by arelationship between the pressure and the flow rate. Thisimplies that simultaneous measurement of intravesicalpressure and flow rate during micturition is required to studyurethral resistance. Up to now, the PFS has been shown tohave good reproducibility, repeatability and has become thegold standard in diagnosing BOO.13 In this study, 64% of the

patients with symptoms consistent with BPE were found tohave obstruction by objective pressure-flow study parameters,which is in accordance with previous reports.6,14

On the other hand, in clinical settings, many patients couldnot void during PFS because human micturition is influencedby many factors, such as environment, psychentonia, bodyposition, and so on. Patients with weak detrusor contractionare also frequent in clinical work. Evaluating the obstructivegrade of these people is still a problem.

UPP is an old method in urodynamic study. It can trace thepressure distribution of the urethral tract at rest. In this studywe found that there was significant difference in P1 and P2between the obstructed and unobstructed group, indicatingthat with the enlargement of prostate, the bladder neck andprostatic urethra were oppressed obviously and urethralresistance increased. By comparison with anatomy, we alsofound that PL on UPP is approximate to the real length of theprostatic urethral tract.15 Our results showed that the PL ofobstructed group was obviously longer than that of theunobstructed group. Undoubtedly, the prolongation of theprostatic urethral tract is another reason for increase inurethral resistance.

There are three male UPP patterns, namely, saddle-, ladder-,and slope-shaped. The percentage of saddle-shaped pattern wasobviously higher in the obstructed group than in the other

Neurourology and Urodynamics DOI 10.1002/nau

Fig. 2. Different types of UPP shapes.

Fig. 3. ROC Curves of UPP parameters in diagnosing BOO. Fig. 4. Distribution of prostatic plateau area in various groups.

844 Fang et al.

groups, which indicates that the bladder neck is the mainobstruction location.

On UPP, both pressure increasing and PL prolonging willincrease the prostatic plateau area (PPA) in the end, a finding

that reflects the urethral resistance at rest since there is nourethral resistance during voiding. ROC curve was used tocompare the sensitivity and specificity of all UPP parametersin diagnosing BOO, PFS result was set as standard. Our datasuggest that all UPP parameters correlated significantlyto the diagnosis of bladder outflow obstruction, which is inagreement with Abrams et al.7 PPA is the most effective tool.When CA �2208.50 mm cmH2O was set as BOO standard, thesensitivity was 100%, but specificity was only 33.2%, whilewhen CA �1439.50 mm cmH2O was set as standard, thesensitivity and specificity were 95.2% and 99.06%, indicatingthat CA �1439.50 mm cmH2O is an effective standard toevaluate BOO due to BPE.

The standardization and reproducibility of UPP is animportant issue. It is known that UPP results are affected bymany factors, such as body position, bladder volume, with-drawal speed, infusion medium, and rate of infusion. Theresults of this study are based on the conditions mentioned inmaterials and methods.

CONCLUSIONS

Our results indicate that PPA on UPP is useful in assessingthe obstruction grade due to BPE when PFS fails. Since thepresent study is a retrospective one, the results should beevaluated by prospective studies.

REFERENCES

1. Abrams P. In support of pressure-flow studies for evaluating men with lowerurinary tract symptoms. Urology 1994;44:153–5.

2. Pel JJ, Bosch JL, Blom JH, et al. Development of a non-invasive strategy toclassify bladder outlet obstruction in male patients with LUTS. NeurourolUrodyn 2002;21:117–25.

3. Digesu GA, Hutchings A, Salvatore S, et al. Pressure flow study: A usefuldiagnostic test for female lower urinary tract symptoms. Neurourlol Urodyn2004;23:104–8.

4. Abrams P, Blaivas JG, Stanton S, et al. The standardisation of terminology oflower urinary tract function. Neurourol Urodyn 1988;7:403–26.

5. Griffiths D. 1996. Pressure-flow studies of micturition. Urol Clin North Am1977;23:279–97.

6. Schafer W, Abrams P, Liao L, et al. Good urodynamic practices: Uroflowmetry,filling cystometry, and pressure-flow studies. Neurourol Urodyn 2002;21:261–74.

7. Hofner K, Tubaro A, de la Rosette JJ, et al. Analysis of outcome afterthermotherapy using different classifications of bladder outlet obstruction.Neurourol Urodyn 1998;17:109–20.

8. Lose G, Griffiths D, Hosker G, et al. 2002. Standardisation of urethral pressuremeasurement. Report from the Standardisation Sub-committee of theInternational Continence Society. Neurourol Urodyn Issue 2.

9. Abrams PH, Torrens MJ. Urethral closure pressure profiles in the male: Ananalysis of 280 patients. Urol Int 1977;32:137–45.

Neurourology and Urodynamics DOI 10.1002/nau

TABLE II. Mean UPP Parameters

Unobstructed(n¼ 168 M� SD)

Equivocal obstructed(n¼ 287 M� SD)

Obstructed(n¼ 826 M� SD)

Total(n¼ 1281 M� SD)

P1 (cmH2O) 14.98 � 3.63 20.13 � 10.84*,** 33.13 � 12.15* 28.07 � 13.15

P2 (cmH2O) 16.95 � 3.84 23.77 � 8.51*,** 30.70 � 10.54* 27.34 � 10.68

MUCP (cmH2O) 112.77 � 11.13 114.97 � 18.23 114.27 � 16.41 114.23 � 16.26

FPL (cm) 4.76 � 0.39 5.26 � 0.58*,** 6.33 � 1.08* 5.89 � 1.12

PL (cm) 3.54 � 0.35 4.03 � 055*,** 5.04 � 1.05* 4.61 � 1.07

PPA (mm cmH2O) 1054.61 � 136.74 1171.97 � 241.68*,** 2052.04 � 445.53* 1724.48 � 583.09

*P< 0.01 versus unobstructed.

**P< 0.01 versus obstructed.

There were significant differences in all UPP parameters between the three groups except MUCP. Mean P1, P2, FPL,

PL, and PPA of the obstructed and equivocal obstructed group were significantly higher than those of the

unobstructed group (P< 0.01).

TABLE III. Distribution of UPP Patterns in Various Groups

Unobstructed(%)

Equivocalobstructed (%)

Obstructed(%)

Saddle-shaped 24.41* 28.57* 71.07

Ladder-shaped 55.95* 46.69* 25.67

Slope-shaped 19.64* 24.74* 3.26

*P< 0.01 versus obstructed.

TABLE IV. Areas Under ROC Curves of UPP Parameters

Test resultvariable (s) Area

Standarderror

Asymptoticsig.

Asymptotic 95%confidence interval

Lowerbound

Upperbound

PPA 0.983 0.004 0.000 0.976 0.990

P1 0.856 0.011 0.000 0.835 0.877

P2 0.798 0.014 0.000 0.771 0.824

PPL 0.852 0.010 0.000 0.832 0.872

MUCP 0.665 0.016 0.000 0.635 0.696

FPL 0.850 0.011 0.000 0.830 0.871

aUnder the nonparametric assumption.bNull hypothesis: true area ¼ 0.5.

TABLE V. Part of Coordinates of the ROC Curve

Test result variable(s)

Positive ifgreater than or

equal to Sensitivity 1-Specificity

PPA (mm cmH2O) 1374.00 0.981 0.092

1406.00 0.971 0.057

1439.50 0.952 0.040

1497.50 0.918 0.040

1503.00 0.915 0.040

2208.50 0.332 0.000

Role of UPP in Evaluating BOO 845

10. Griffiths D. Urodynamic assessment of bladder function. Br J Urol 49:29–36.11. Schafer W. 1983. Detrusor as the energy source in micturition. In: Hinman F,

Jr., editor. Benign Prostatic Hypertrophy. New York: Springer, 450–69.12. Schafer W. Urethral resistance? Urodynamic concepts of physiological and

pathological bladder outlet function during voiding. Neurourol Urodyn1985;4:161–201.

13. Digesu GA, Hutchings A, Salvatore S, et al. Pressure flow parameters infemale: Reliability studies. Br J Obstet Gynaecol 2003;110:774–6.

14. Van-Mastrigt R, Rollema HJ. The prognostic value of bladder contractility intransurethral resection of the prostate. J Urol 1992;148:1856–60.

15. Bo S, Xiyu J, Xuwei Zh, et al. Study on the role of cystometry and UPP on BPHpatients. Chinese J Clinical Urol 1992;7:225–6.

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846 Fang et al.