Transrectal Ultrasound In Assessment Of Bladder Outlet Obstruction Via Intravesical Prostate Protrusion

Objective: Benign prostatic hyperplasia (BPH) is a common and frequently encountered disease of middle-aged and elderly men. And the prostatic protrusion into the urinary bladder is a special type. The main reason for lower urinary tract obstructive symptom due to BPH is bladder outlet obstruction (BOO) or the destruction of bladder detrusor. And the therapy is different for different reasons. It is important to find the real reason that can provide the reliable gist for the clinical therapy. Urodynamic study is regarded as the'gold standard'for BOO nowadays. But it doesn't widely used in clinics for it's invasive and costly. Recently transrectal ultrasound (TRUS) which is low invasive, cheap and convenient has made great progresses in diagnosing BOO. The study was designed to assess the significance of TRUS for the diagnosis of BOO due to benign prostatic hyperplasia via intravesical prostatic protrusion (IPP).Methods: The data of 110 patients with lower urinary symptoms and the prostate volume above 30 cm3 were enrolled and divided into two patterns (obstruction and non-obstruction), which is according to the urodynamic study. Each pattern was divided into three grades according to the extent of IPP(gradeⅠtoⅢ). The IPP, the ratio between IPP and the vertical length of the prostate (IPPR) and other morphologic parameters (the total prostate volume(TPV), the transition zone volume(TZV), the transition zone index(TZI), the presumed circle area ratio(PCAR), transition and peripheral anteroposterior diameter ratio(T/PA), transition and peripheral area ratio(T/PS)) were measured; The left and right capsular and urinary artery resistive indices were detected by transrectal power Doppler. The Abrams-Griffths(AG) number were determined by urodynamics. Thelogistic regression with the transrectal variables according to the AG value was analysed. Results:1. In all, 68 patients had significant BOO, defined as a BOO index of >40. Of these men,12 had gradeⅠ,25 had gradeⅡand 31 had gradeⅢ;42 patients had a BOO index of <40,32 had grade I and 10 had gradeⅡ.2.No significant difference in RI was observed between right and left transition and peripheral zones in the prostate( P>0.05) .There was a significant difference in IPP,IPPR,TZI,PCAR,T/PA,T/PS,CRI,URI between obstruction and non-obstruction groups(P<0.05).3.By the logistic regression, the main factors of bladder outlet obstruction were IPPR and the CRI. And then developed a formula (Y=1/(1+e^-z), Z=28.432- 40.962×IPPR- 34.908×CRI) by defining the cutoff for Y at 0.2 to predicted BOO with the positive predict value of 93%, negative predict value of 51%,and overall accuracy of 81%. In BOO group, the value of Y inⅢgrade is lower than that inⅠgrade andⅡgrade, which indicate that the extent of BOO inⅢgrade is more heavy thanⅠgrade andⅡgrade.Conclusions: Among the many indices measured by TRUS, the IPPR and CRI are more close to BOO than others. The logistic formula Y=1/(1+e^-z) , Z=28.432 - 40.962×IPPR - 34.908×CRI by defining the cutoff for Y at 0.2 provide important positive BOO prediction rate of 87.5%, negative prediction rate of 73.9% and accuracy of 81.8%. In BOO group, the extent of BOO inⅢgrade is more heavy thanⅠgrade andⅡgrade. The IPPR correlated with CRI are meaningful indices for BOO diagnosed. Additional studies with large cohorts are required to validate the feasibility of this method.