IMAGING

doi: 10.1590/S1677-55382010000600020

Ultrasound assessment of intravesical prostatic protrusion and detrusor wall thickness--new standards for noninvasive bladder outlet obstruction diagnosis?
Franco G, De Nunzio C, Leonardo C, Tubaro A, Ciccariello M, De Dominicis C, Miano L, Laurenti C
Department of Urology, La Sapienza University, Rome, Italy
J Urol. 2010; 183: 2270-4

• Purpose: We evaluated the accuracy of detrusor wall thickness and intravesical prostatic protrusion, and the association of each test to diagnose bladder prostatic obstruction in patients with lower urinary tract symptoms.
  Materials and Methods: We enrolled in the study 100 consecutive patients with lower urinary tract symptoms due to benign prostatic hyperplasia. Baseline parameters were International Prostate Symptom Score, prostate volume, urinary flow rate, intravesical prostatic protrusion, detrusor wall thickness, Schaefer obstruction class, minimal urethral opening pressure and the urethral resistance algorithm bladder outlet obstruction index. A ROC curve was produced to calculate AUC and evaluate the diagnostic performance of intravesical prostatic protrusion, detrusor wall thickness and prostate volume for bladder prostatic obstruction.
  Results: We noted a highly significant correlation between intravesical prostatic protrusion and the bladder outlet obstruction index (Spearman’s rho = 0.49, p = 0.001), and Schaefer obstruction class (Spearman’s rho = 0.51, p = 0.001). A highly significant correlation was also observed for detrusor wall thickness and the bladder outlet obstruction index (Spearman’s rho = 0.57, p = 0.001), detrusor wall thickness and Schaefer obstruction class (Spearman’s rho = 0.432, p = 0.02). On multivariate analysis intravesical prostatic protrusion and detrusor wall thickness were the only parameters associated with bladder prostatic obstruction (p = 0.015). The AUC for intravesical prostatic protrusion was 0.835 (95% CI 0.756-0.915) and for detrusor wall thickness it was 0.845 (95% CI 0.78-0.91). The association of intravesical prostatic protrusion and detrusor wall thickness produced the best diagnostic accuracy (87%) when the 2 tests were done consecutively.
  Conclusions: Suprapubic ultrasound of detrusor wall thickness and intravesical prostatic protrusion is a simple, noninvasive, accurate system to assess bladder prostatic obstruction in patients with lower urinary tract symptoms due to benign prostatic hyperplasia.

• Editorial Comment
  Recently attempts have been made to provide noninvasive tests for the assessment of bladder outlet obstruction (BOO). Since prostate volume and post void residual urine are not accurate parameters in predicting BOO, the positive predict value of others sonographic measurements such detrusor wall thickness (DWT), bladder weight and intravesical prostatic protrusion (IPP) has been investigated. In this study the authors evaluated a group of 100 patients with lower urinary tract symptoms due to benign prostatic hyperplasia. They found that the AUC for IPP was 0.835 with a cutoff of 12 mm having 0.65 sensitivity and 0.77 specificity and 88% positive predictive value. The AUC for DWT was 0.845 and at a 6 mm cutoff they noted 0.73 sensitivity and 0.82 specificity. Patients with 1 of the 2 tests positive (IPP 12 mm or more, or DWT 7 mm or more) have an approximately 90% chance of bladder prostatic obstruction on pressure flow study. In the evaluation of IPP, the authors excluded men with a median lobe, which may cause ball valve type of obstruction and can be easily determined by suprapubic US in the sagittal plane. Special attention was given to the role of protrusion of lateral lobes into the bladder. Radiologists and urologists, who perform urological ultrasound, should be aware of the technical aspects of how to obtain these measurements. The estimative of DWT, is yet the only one of these two parameters which has been recommended by the “American College of Radiology 2008 - Appropriateness Criteria”, requires adequate maximum bladder volume, adequate place of the transducer for bladder wall measurement and optimized ultrasound transducer frequency.

Dr. Adilson Prando
Head, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com