Which Is a Better Indicator of Bladder Outlet Obstruction in Patients with Benign Prostatic Enlargement - Intravesical Protrusion of Prostate or Bladder Wall Thickness?

Abstract

Objective: to determine the correlation of intravesical prostatic protrusion (IPP) and bladder wall thickness (BWT) with clinical and urodynamic parameters, as well as their sensitivity and specificity with regard to bladder outlet obstruction in patients with a benign prostatic enlargement (BPE). Materials and methods: 111 patients with lower urinary tract symptoms and confirmed BPE completed the International Prostatic Symptom Score (I-PSS), as well as a transabdominal ultrasound to determine their prostate volume, a grade of IPP and BWT. All the patients were then subjected to the complete urodynamic studies (UDS). Results: the IPP showed a good correlation with the prostate volume (r=0.61) and serum PSA (r=0.48); p=0.0000, free uroflowmetry (r=-0.27; p=0.004), as well as the determinants of urodynamic obstruction: bladder outlet obstruction index-BOOI (r=0.36; p<0.0001), and ICS and Schaefer obstruction class nomograms (rho=0.33 and rho=0.39, respectively; p<0.001), while the BWT showed only a statistical correlation with age (r=0.23; p=0.02) and serum PSA (r=0.4; ,p=0.0000), regardless of an significant correlation with the IPP (r=0.45; p=0.0000). The ANOVA test showed a significant difference between the IPP grades for the observed clinical and urodynamic variables with an increase in significance for IPP>10 mm. The area under the ROC curve in the prediction of obstruction for the IPP is 0.71 (sensitivity 59.6, specificity 81.4), while the AUC for the BWT is 0.61 (sensitivity 64.5, specificity 59.2). The stepwise logistic regression model shows that most significant independent variables for the obstruction are the IPP, Qmaxfree and age, with the area under the ROC curve of 0.78 (95% CI 0.695 to 0.856). Conclusion: The IPP higher than 10 mm as a non-invasive predictor of infravesical obstruction shows good correlations with clinical and urodynamic parameters, while the specificity and PPV against obstruction are significant. Despite a good correlation with IPP, the BWT is only a modest indicator of obstruction.

Which Is a Better Indicator of Bladder Outlet Obstruction in Patients with Benign Prostatic Enlargement

DOI: 10.5455/medarh.2012.66.324-328 Med Arh. 2012 Oct; 66(5): 324-328 Received: June 18th 2012Accepted: August 29th 2012

CONFLICT OF INTEREST: NONE DECLARED

ORIGINAL PAPER

Which Is a Better Indicator of Bladder Outlet Obstruction in Patients with Benign Prostatic Enlargement Intravesical Protrusion of Prostate or Bladder Wall Thickness?

Damir Aganovic, Munira Hasanbegovic, Alden Prcic, Benjamin Kulovac, Osman Hadziosmanovic Urology clinic, Clinical Centre of University of Sarajevo, Bosnia and Herzegovina

Objective: to determine the correlation of intravesical prostatic protrusion (IPP) and bladder wall thickness (BWT) with clinical and urodynamic parameters, as well as their sensitivity and specicity with regard to bladder outlet

obstruction in patients with a benign prostatic enlargement (BPE). Materials and methods: 111 patients with lower urinary tract symptoms and conrmed BPE completed the International Prostatic Symptom Score (I-PSS), as well as a transabdominal ultrasound to determine their prostate volume, a grade of IPP and BWT. All the patients were then subjected to the complete urodynamic studies (UDS). Results: the IPP showed a good correlation with the prostate volume (r=0.61) and serum PSA (r=0.48); p=0.0000, free uroowmetry (r=-0.27; p=0.004), as well as the determinants of urodynamic obstruction: bladder outlet obstruction indexBOOI (r=0.36; p<0.0001), and ICS and Schaefer obstruction class nomograms (rho=0.33 and rho=0.39, respectively; p<0.001), while the BWT showed only a statistical correlation with age (r=0.23; p=0.02) and serum PSA (r=0.4; ,p=0.0000), regardless of an signicant correlation with the IPP (r=0.45; p=0.0000). The ANOVA test showed a signicant dierence between the IPP grades for the observed clinical and uro-dynamic variables with an increase in signicance for IPP>10 mm. The area under the ROC curve in the prediction of obstruction for the IPP is 0.71 (sensitivity 59.6, specicity 81.4), while the AUC for the BWT is 0.61 (sensitivity 64.5, specicity 59.2). The stepwise logistic regression model shows that most signicant independent variables for the obstruction are the IPP, Qmaxfree and age, with the area under the

ROC curve of 0.78 (95% CI 0.695to0.856). Conclusion: The IPP higher than 10 mm as a non-invasive predictor of infravesical obstruction shows good correlations with clinical and urodynamic parameters, while the specicity and PPV against obstruction are signicant. Despite a good correlation with IPP, the BWT is only a modest indicator of obstruction. Key words: benign prostatic enlargement, intravesical prostatic protrusion, bladder wall thickness, UDS.

Corresponding author : Prof. Damir Aganovic, MD, PhD. Department of Urology, CCUS, Bolnicka 25, Sarajevo, Bosnia and Herzegovina, tel. ++38733 297 754, E-mail: [email protected]

1. INTRODUCTION

A benign prostatic enlargement shows an increase in incidence with age, causing lower urinary tract symptoms (LUTS) and infravesical obstruction (1). The most precise tool of diagnosing a bladder outlet obstruction are urodynamic studies (UDS), which are, however, invasive, costly, time consuming, and can also lead to a certain degree of morbidity (2). Furthermore, the relationships among urodynamic parameters, treatment outcome and symptom relief are still a subject of controversy. The ISC recommends pressure ow studies before invasive therapies or when a precise diagnosis of bladder outlet obstruction is important (3). Considering the above, it has recently been insisted on searching for non-invasive modalities in bladder outlet obstruction prediction. They rely on a combination of radiological and clinical indicators or on non-invasive urodynamics (4). One of such non-invasive indicators is the ultrasound-conrmed intravesical prostatic protrusion (IPP) and bladder wall thickness (BWT), which according to some studies show a good prediction

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towards obstruction (5, 6), compared to

urodynamic studies.

Owing to the above, a prospective study was conducted in order to determine the correlation between these determinants with clinical and urodynamic variables and to assess the sensitivity and specicity of IPP and BWT in relation to infravesical obstruction due to BPE.

2. MATERIALS AND METHODS

During the period 2009-2010, the total of 111 patients from daily urological practice were selected at the Urology Clinic of the Sarajevo University Hospital. The patients mean age was 65.4 years (48-82), and they had lower urinary tract symptoms (LUTS) and conrmed benign prostatic enlargement (BPE). The exclusive criteria were clear neurological or endocrine diseases, suspect bladder cancer or calculosis, urethral stenosis, suspect prostate carcinoma, urinary infection, advanced kidney failure, previous operation of the prostate, as well as taking medications interfering with urination. The transabdominal ultrasound (TAUS) determined their prostate volume, as well as intravesical protrusion of the prostate (IPP). The IPP was determined at the bladder volume of 150-200 ml, moving the saggital scan of the ultrasound probe horizontally and longitudinally, examining the vesical neck in terms of prostate protrusion into the bladder. The IPP was dened by the distance from the tip of the prostates protrusion into the vesical lumen to the bladder neck measured in millimetres, determining the following three stages of IPP: <5mm grade I, 5-10 mm grade II, and >10 mm grade III. Bladder wall thickness (BWT) was determined at the full bladder capacity. Prior to the urodynamic studies (UDS), the patients signed the Informed Consent and completed International Prostatic Symptom Score (I-PSS). All the patients were prophylactically given Ciprooxacin tbl a 500 mg. This was followed by free uroowmetry (with the minimum of 150 ml of urine voided) and determination of the postvoid residual urine (PVR). The examination continued with cistometry (CMG). The bladder lling

and measuring of the intravesical pressure during lling and urination were performed by introducing the Nelaton Ch8 catheter (Dalhausen & Co, GmbH, Koln, Germany- infusion line) and Nelaton Ch5 urethral catheter (Web-singer GmbH, Wiena, Austria-transducer line) into the bladder tandem or rail-road technique (7). The abdominal pressure was determined by introducing the standard rectal balloon catheter. The CMG was performed in sitting position with the lling rate of 25ml/ min. Before urination, the patients Ch8 catheters were removed. Then the ndings of pressure/ow studies (PFS) were plotted on the Schaefer obstruction class and ICS nomograms, followed by the determination of the bladder contractility index (BCI=PdetQmax +5Qmax), bladder voiding efficiency (BVE=voided volume/total bladder capacity x100), and the bladder outlet obstruction index (BOOI= PdetQmax -2Qmax) (8). The

UDS, unless otherwise specied, were based on the International Continence Society methodology and terminology (9). Statistical analysis was performed through correlation tests, ANOVA test, area under ROC curve, stepwise logistic regression model using Medcalc program for Windows version 12. The level of signicance (two-tailed) was set at p < 0.05.

3. RESULTS

The main clinical and demographic characteristics of the patients are given in Table 1. The IPP mean value was 11.8mm (11.2), with the BWT mean value of 5.2 mm (1). 17 patients (15.3%) had the IPP <5 mm, 30 patients (27%) had the IPP in the range of 5-10 mm, and 64 patients (57.7%) had the IPP >10 mm. At the same time, according to the BOOI <20, 20 patients (18%) was out of obstruction, while 37 (33.3%) and 54 patients (48.6%) were in non-classied and obstruction zone, respectively, (BOOI 20-40 and >40). According to the BOOI obstruction levels, the Kruskal Wallis test showed a signicant dierence in the IPP size (Figure 1). The IPP mean value in the zone out of obstruction was 8.8 (4.1) mm, in the non-classied zone the IPP was 9.9 (5) mm, and in the zone of clear obstruction 14.3 (7.6) mm (p=0.0005). The patients were then

dichotomised in groups with the cut-o value of IPP >10 mm. The mean BOOI for the group with IPP<10 mm was 35.6 (24.9), while the mean BOOI for the group with IPP>10 mm was 49.8 (29); T test 6.1 (p=0.0009). Furthermore, there was a statistically signicant linear regression between these two factors (Figure 2).

Clinical and demographics characteristics

Arithmetic mean (SD), Median

classified zone the IPP was 9.9 (5) mm, and in the zone of clear obstruction (p=0.0005). The patients were then dichotomised in groups with the cutmm. The mean BOOI for the group with IPP<10 mm was 35.6 (24.9),for the group with IPP>10 mm was 49.8 (29); T test 6.1 (p=0.0009). statistically significant linear regression between these two factors (Figure 2)

Clinical and demographics

characteristics

Arithmetic mean (SD),

Median

Range

Range

Age (years) 65.4 (7.5); 67 48-82

PSA (ng/ml) 2.3 (1.5); 1.9 0.2-6.3

PV(cc) 47.4 (22); 41 25-120

I-PSS 18.2 (5.8); 19 6-31

Qmax free (ml/sec) 9.1 (4.4); 8.1 2.1-25

BWT (mm) 5.2 (1); 5.4 2.2-6.8

PVR (ml) 50.1 (52.3); 31 0-250

IPP (mm)

11.76 (6.6); 11.2

1-32

PSA-Prostate specic antigen, PV-prostate volume, I-PSS International prostatic symptom score, Qmax free-maximum urinary ow, BWT-bladder wall thickness, PVR-post void residual urine IPP intravesical prostrusion of prostate

Table 1. Basic clinical and demographics characteristic of the BPE group

Age (years) 65.4 (7.5); 67 48-82 PSA (ng/ml) 2.3 (1.5); 1.9 0.2-6.3 PV(cc)

47.4 (22);

41

25-120

I-PSS

18.2 (5.8);

19

6-31

Q free (ml/sec)

9.1 (4.4);

8.1

2.1-25

BWT (mm) 5.2 (1); 5.4

2.2-6.8

PVR (ml) 50.1 (52.3); 31

0-250

IPP (mm) 11.76 (6.6); 11.2

1-32

PSA-Prostate specific antigen, PV-prostate volume, I-PSS International prostatic symptom score

maximum urinary flow, BWT-bladder wall thickness , PVR-post void residual urine IPP

prostate

Table 1. Basic clinical and demographics characteristic of the BPE group

IPP values according to the BOOI

0

40

35

30

25

IPP

20

15

10

5

<20

1

20-40

2

>40

3

Bladder outlet obstruction index

Figure 1. IPP values according to the bladder outlet obstruction index

Figure 1. IPP values according to the bladder outlet obstruction index

40

35

r=0,3636; p=0,0001

y 8,0067 + 0,08522 x

30

25

IPP

20

15

10

5

0

-20 0 20 40 60 80 100 120 140

BOOI

Figure 2. Linear regression for IPP and bladder outlet obstruction index (BOOI)

Figure 2. Linear regression for IPP and bladder outlet obstruction index (BOOI)

A correlation analysis of IPP with clinical and urodynamic parameters showed a good and statistically significant correlation with the prostate volume, serum PSA,correlation with IPS score (or its obstructive and irritative subgroups). Out of the urodynamic parameters the IPP shows a statistically significant correlation with Qmax

capacity, PdetQmax, BVE, BCI and pressure at minimal urethral opening (Pmuo Spearman rank correlation coefficient

showed a significant correlation between the ICS nomogram and Schaefer obstruction class

(LinPURR) with the values of (p=0.0005) and rho=0.39 (p<0.0001), respectively.

There is a good correlation of IPP with

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325

within the obstruction region, so that the area under the curve (AUC) for BWT is 0. sensitivity 64.5 and specificity 59.2, similarly to the discriminant value of age with the area of0.60. Prostate volume shows the weakest discrimination with regard to obstruct3).

Intravesical Protrusion of Prostate or Bladder Wall Thickness?

Comparison of discriminant validity for the obstruction

0 20 40 60 80 100

100

80

60

40

AgeBWTIPP Prost.vol.

20

0

100-Specificity

IPP (mm) BWT (mm) Pearson Corr.

coef. r p r p Age 0.08 0.38 0.23 0.02 IPSS 0.05 0.6 0.17 0.08 PV (cc) 0.61 0.0000 0.25 0.007 PSA (mg/ml) 0.478 0.0000 0.4 0.0000 Qmax free (ml/sec) -0.27 0.004 -0.18 0.06

PVR (ml) 0.14 0.14 0.08 0.37 Cyst.Cap (ml) 0.19 0.048 -0.07 0.49

BC (ml/cmH2O) -0.11 0.24 -0.03 0.78

DO 0.08 0.43* 0.04 0.6* Pmuo (cm/H2O) 0.19 0.04 0.06 0.5 PdetQmax (cm/H2O) 0.37 0.0001 0.1 0.29

DCD (sec) 0.212 0.03 -0.016 0.8 BVE -0.2 0.03 -0.19 0.04 BCI 0.21 0.02 0.01 0.9 BOOI 0.36 0.0001 0.15 0.12

* Spearman (rho) corr.coefcient. IPP-intravesical prostrusion of prostate, , BWT-bladder wall thickness, PV-prostate volume, Qmax-peak urinary ow, PVR-post void residual urine, Cyst.Cap.-cystometric capacity, BC-bladder compliance, DO-detrusor overactivity, Pmuo- minimal urethral opening pressure, PdetQmax-detrusor pressure at Qmax, DCD-detrusor contraction duration, BVE-bladder voiding efciency, BCI-bladder contractility index

Sensitivity

Figure 3. ComparisonofROCcurves

Figure 3. Comparison of ROC curves

The applied stepwise logistic regression analysis for bladder outlet dependent variable) showed that statistically most significant variables are the

Table 2. Correlation analysis of IPP and BWT with clinical and urodynamic parameters

No pat. 111

A correlation analysis of IPP with clinical and urodynamic parameters showed a good and statistically signicant correlation with the prostate volume, serum PSA, while there was no correlation with IPS score (or its obstructive and irritative subgroups). Out of the urodynamic parameters the IPP shows a statistically signicant correlation with Qmax free, cystometric capacity, PdetQmax, BVE, BCI and pressure at minimal urethral opening (Pmuo) (Table 2). Spearman rank correlation coefficient showed a signicant correlation between the IPP and ICS nomogram and Schaefer obstruction class (LinPURR) with the values of rho=0.33 (p=0.0005) and rho=0.39 (p<0.0001), respectively. There is a good correlation of IPP with BWT (r=0.45; p=.0000), although the BWT does not show signi-cant correlations with clinical and uro-dynamic parameters, except with the patient age, PSA, and shows a weak statistically inverted correlation with BVE (Table 2.). Detrusor overactivity (DO) does not show a correlation with the IPP or with the BWT.

Trichotomising the patients according to the IPP size, the ANOVA test showed signicant dierences in the prostate volume, Qmax, BWT, PSA and PdetQmax, with a signicant obstruction increment towards the IPP transition levels. While the mean BOOI for the groups with IPP<5mm and IPP 5-10 mm

in the non-classied region is 35.5 and 35.8, the mean BOOI of 50.4 is indicative of an advanced obstruction for the group of patients with IPP>10 mm (p=0.03) (Table 3). Even though the dierences in postvoid residual urine are not statistically signicant, there is a growth trend from the mean volume of 45 and 36 ml for the rst two groups towards a larger quantity of residual urine in the third group (56.6 ml). Detrusor overactivity does not show an incidence increase towards the IPP transition values.

The determination of the discriminant validity of IPP according to the obstruction (BOOI>40) led to the calculation of the area under ROC curve for the IPP in obstruction prediction of 0.71 (95% CI 0.615 to 0.791); p=0.0001, (Sensitivity 59.6, Spec-icity 81.4, +LR 3.2, -LR 0.5, PPV 73.8, and NPV 69.6).

The value of 5 mm was taken as the cut-o value according to the obstruction for BWT. 33 patients (57.9%) outside obstruction had the value of BWT >5mm, and 36 patients (66.7%) within the obstruction region, so that the area under the curve (AUC) for BWT is 0.61 with sensitivity 64.5 and specificity 59.2, similarly to the discriminant value of age with the area of 0.60. Prostate volume shows the weakest discrimination with regard to obstruction (Figure 3).

The applied stepwise logistic regression analysis for bladder outlet

IPP <5mm (17) Mean (SD), Med. (range)

IPP 5-10 mm(30) Mean (SD), Med. (range)

IPP> 10 mm (64) Mean (SD), Med. (range)

Anova (F) p

Age 63.5 (7.2)

66 (48-72)

64.3 (8.5)64.5 (48-75)

66.4 (7) 67 (52-82)

1.50.2

IPS Score 16.5 (6.8)

15 (6-31)

19.1 (5.4)

20 (10-27)

182. (5.6)

19 (8-28)

1.10.3

P V(cc) 29.7 (9.7)

26 (20-56)

41.7 (16.4) 38 (24-111)

54.8 (23.3) 49 (24-120)

8.3 <0.001

Qmax (ml/sec.) 11.9 (6)

10.5 (4.3-25)

8.9 (3.2)9.2 (4.6-17)

8.5 (4.1)7.7 (2.1-18.9)

4.40.016

BWT (mm) 4 (0.7)

4 (2.2-4.8)

4.9 (1)4.8 (2.2-6.6)

5.6 (0.8)5.9 (2.4-6.8)

25.3 <0.001

PSA (ng/ml) 1.3 (1)

1 (0.2-3.4)

2 (1.2)1.8 (0.4-4.8)

2.8 (1.7)2.5 (0.4-6.3)

8.3 <0.001

1.50.23

DO 5 (29.4%) 10 (34%) 24 (37.6%) 0.44

0.8*

Cyst. Cap. (ml) 259.7 (64.4)

257 (152-356)

230.4 (60) 228.5 (121-390)

257 (66.8) 253 (112-462)

PVR (ml) 45.3 (59.8)

20 (10-185)

36.7 (46) 25 (2-250)

56.6 (52.6)37.5 (0-212)

20.14

BC (ml/cmH2O) 31.8 (14.3)

35 (11-56)

34.4 (15.3)

40 (10-56)

31.7 (15)34.5 (4-67)

0.350.7

PdetQmax(cmH2O) 53.8 (13.9)

54 (35-79)

51.9 (24)45.5 (17-130)

66.5 (25.5) 62 (23-148)

4.70.01

Pmuo (cmH2O) 31.5 (12.6)

29 (14-57)

24.7 (12.2) 23 (4-49)

40.4 (42)29.5 (3.4-126)

2.40.09

BOOI 35.5 (25.2)

32 (2-107)

35.8 (25) 29 (2-112)

50.4 (29) 45 (-2-131)

3.70.03

* Chi2 test. PV-prostate volume, Qmax-peak urinary ow, BWT-bladder wall thickness, PVR-post void residual urine, Cyst. Cap.-cystometric capacity, BC-bladder compliance, DO-detrusor overactivity, PdetQmax-detrusor pressure at Qmax, Pmuo- minimal urethral opening pressure , DCD-detrusor contraction duration, BOOI-bladder outlet obstruction index

Table 3. Differences of clinical and urodynamic variables according to the grades of IPP

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obstruction (as a dependent variable) showed that statistically most signi-cant variables are the IPP (p=0.01, OR 1.1), Qmaxfree (p=0.01, OR 1.1) and age (p=0.03, OR 0.3), with log likelihood of -28.8, (p<0.0001). The signicance level for the Hosmer & Lemeshow test is high (p=0.6; >0.1), indicating a good logistic regression model t. The area under the ROC curve for these variables is 0.78 (95% CI 0.695to0.856). Saved predicted probabilities and their use as a new variables increase AUC to 0.88. The variables excluded from this model were BWT, BCI, PVR and prostate volume.

4. DISCUSSION

Benign prostatic hyperplasia affects the expression of lower urinary tract symptoms. Nevertheless there are no signicant correlations between the symptoms and clinical and urodynamic parameters characterising mechanical obstruction (10). Owing to this, non-invasive prostate measurements are made in order to further explain morphofunctional correlations, trying to develop a new precise method that could replace the standard urodynamic studies, thus reducing the costs, increasing availability and reducing patients discomfort. Since the bladder outlet obstruction (BOO) is a dynamic event caused both by mechanical obstruction and by bladder functioning, there is the rationale for including the anatomic evaluation of the prostate and bladder as part of the assessment (5).

It has become known that the prostatic conguration together with the expressed IPP can inuence normal urination. The IPP seems to support infra-vesical obstruction through the valve ball mechanism, in which prostatic lateral and median lobes interfere with the complete opening of the vesical neck during urination, disrupting the funnelling eect of the bladder neck and causing dyskinetic movement of the bladder during voiding (11).

Literature reports a wide range of the conrmed IPP grade III; thus Reis et al. nd the incidence for IPP gr. I of 28.5%, 12% grade II and 59.5% IPP gr. III (12), while Liebber et al. nd only 10% of patients with IPP gr. III (13), and Kim nds the incidence gr. III of

IPP in 15% of patients (14). Chia et al. show that out of 125 patients who were diagnosed as having signicant BOO (BOOI >40), 95 had grade III (76%) and 30 grade III IPP. Our study shows the incidence of IPP grade III of 57.7% within the observed sample, with the mean value of IPP amounting to 14.3 mm, in patients within the obstruction zone (BOOI>40). The mean value of BOOI for grade III of IPP amounted to 50.4 vs. 35.8 and 35.5 for grade II and grade I, respectively. Furthermore, the IPP correlates well with the obstruction determinants (the correlation coefficient for the BOO index and IPP is 0.37, p<0.0001, as well as a clearly demonstrated correlation with the ICS and Schafer nomogram). Chia et al., exploring the benet of the intravesical prostatic protrusion in 200 patients, show that the IPP is a statistically signicant predictor (p< 0.001) of bladder outlet obstruction, and grade III IPP was associated with a higher BOO index than was grade III (BOOI 67.15 vs. 43.13, p < 0.001) (5). Franco et al. nd good correlations between intravesical prostatic protrusion and the bladder outlet obstruction index (Spearmans rho = 0.49, p=0.001), and Schaefer obstruction class (Spearmans rho = 0.51, p = 0.001) (15).

This study shows that the IPP has

a good correlation with age, prostate volume (PV), maximum urinary ow, postvoid residual urine, and oers statistically signicant correlations with the main urodynamic parameters typical of obstruction, but also of the bladder functioning (Pmuo, Pdet Qmax, BVE and BCI; p<0.05). Han et al., examining mutual correlations of IPP with other clinical variables in 257 patients, show that the degree of IPP correlated positively with age (r = 0.210, p < 0.01), prostate volume (r = 0.534, p < 0.01) and PVR (r = 0.314, p <0.01), while negatively with the Qmax (r = -0.364, p < 0.01). There was no signicant correlation between the degree of IPP and IPSS (r = 0.064, p=0.299) (16), just as our study shows no correlation of IPP and I-PSS; (r=0.05, p=0.6). Kim et al. nd only a statistically signicant correlation between the IPP and IPSS, but with no dierence between the obstructive and irritative domain of the question-

naire (17). Again, Kim (14) suggests that IPP, which reects anatomical changes in the prostate, may be related to male symptoms of overactive bladder (OAB), dening the OAB in patients who complained of symptoms with 2 points or more for the 4th questionnaire related to urgency on the IPSS.

The IPP appears to be a very valuable and reproducible ultrasound feature, as part of the infravesical obstruction examination in patients with BPE. A high IPP grade can also be a strong outcome predictor after acute urinary retention (AUR) treated with trail without catheter (TWOC). Mariappan et al. shows that the TWOC is more likely to fail in patients with intravesical prostatic protrusion larger than 10 mm, because men with IPP 10 mm or less, compared to those with a larger intravesical prostatic protrusion, were 6 times more likely to have a successful trial without catheter (18). Furthermore, since intravesical prostatic protrusion signicantly correlates with greater prostate volume, higher obstructive symptoms and lower peak urinary ow rate, it suggests that it may have clinical usefulness in predicting the need for treatment (13).

According to some researchers, bladder wall thickness (BWT) of 5 mm appears to be the best cut-o point u diagnosing BOO, carrying a high sensitivity and specicity (19). Franco et al. demonstrate that the detrusor wall thickness (DWT) is an excellent predictor of BOO, with AUC for DWT of 0.845, and a good correlation with the Schaefer obstruction class (Spearmans rho = 0.432, p = 0.02) (15). Oelke et al. measured detrusor wall thickness and found that over 95% of patients with the detrusor thickness higher than 2 mm were in urodynamic obstruction (6). According to Kim et al. higher BWT grades showed signicant dierences with higher PV, serum PSA and IPSS (p<0.05). Furthermore, BWT >5 mm was associated with higher PVR and acute urinary retention (17). Our study did not show a strong discriminant power of BWT in relation to obstruction, as the AUC for BWT is only 0.61 (sensitivity 64.5 and specificity 59.2), and in addition to a good correlation with the IPP, there is only a statistically signicant correlation with age

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Intravesical Protrusion of Prostate or Bladder Wall Thickness?

and serum PSA. Some researchers did not nd a dierence in the mean value of BWT between patients with normal UDS ndings, infravesical obstruction or DO. The inconsistency in obtained results and a lack of technique standardization are limiting the use of BWT as a strong predictor of infravesical obstruction for the time being (12).

There is also the issue of the manner of ultrasound IPP determination. Some studies show an extended use of transrectal ultrasound (TRUS) in prostate measuring (13, 21.) Since the transrectal measuring causes a greater discomfort to patients, transabdominal ultrasound (TAUS) is shown to be equivalent to rectal ultrasound when the prostate is measured at the bladder volume above 100 ml (22). TAUS is now a common clinical method, noninvasive and easy to learn and evaluate. Using the same probe, the upper urinary tracts can be easily assessed at the same time. (5). Foo also concludes that the degree of IPP can be measured non-invasively in the midsagittal plane, and can be graded accordingly. Diagnosis of BPE in the clinic can be aided by simple, non-invasive, transabdominal ultrasound (23).

5. CONCLUSION

This study has demonstrated the use of assessing the intravesical prostatic protrusion in predicting infravesical obstruction in patients with BPE. It shows a good correlation of IPP with clinical and urodynamic variables, as well as high specicity and positive predictive value in terms of obstruction by the IPP grade increase, while the determination of the bladder wall thickness shows this parameter to be only a modest indicator of bladder outlet obstruction.

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Med Arh. 2012 Oct; 66(5): 324-328 ORIGINAL PAPER