Residual fraction as a parameter to predict bladder outlet obstruction in men with lower urinary tract symptoms.
OBJECTIVE
To determine whether noninvasive tests including the residual fraction are reliable for the diagnosis of bladder outlet obstruction (BOO).


METHODS
A total of 212 men (median age 68, range 44-89 years) were included in the present study. The median serum prostate-specific antigen level and prostate volume were 1.3 ng/mL (range 0.2 to 9.4) and 37.9 mL (range 11.3 to 148.0), respectively.


RESULTS
Among the variables analyzed in the multivariate model, the likelihood of BOO varied by the total prostate volume, with a 3.6-fold higher odds for >or=40 mL than for <40 mL (odds ratio [OR], 3.616; 95% confidence interval [CI], 1.217-10.749; P = 0.021). In the same model, a low maximal flow rate (Qmax) (OR, 2.840; 95% CI, 1.260-6.401; P = 0.012) and high residual fraction (OR, 7.103; 95% CI, 1.924-26.225; P = 0.003) were associated with an increased likelihood of BOO. The sensitivity and specificity for predicting BOO using a total prostate volume of 40 mL or greater were 73.7% and 65.2%, respectively. Using a Qmax cut-off of 12 mL/s or less for predicting BOO, the sensitivity and specificity were 77.2% and 54.2%, respectively. Prediction of the BOO by the residual fraction only had a sensitivity and specificity, for a residual fraction of less than 20%, of 75.4% and 67.7%, respectively.


CONCLUSIONS
The presence or absence of BOO might be predicted using non-invasive methods. The residual fraction may help with patient management by better predicting the likely patient classification from pressure-flow studies.
Ku
Ja Hyeon
JH
Department of Urology, Seoul National University College of Medicine, Seoul, Korea.
Cho
Sung Yong
SY
Oh
Seung-June
SJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood*; D012189:Retrospective Studies; D012212:Rheology; D012680:Sensitivity and Specificity; D036761:Ultrasound, High-Intensity Focused, Transrectal; D001748:Urinary Bladder Neck Obstruction / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D014555:Urination Disorders / Q000209:etiology* / Q000503:physiopathology; D014563:Urodynamics / Q000502:physiology*
D017430:Prostate-Specific Antigen