To describe distinctive morphologic variations of the prostate associated with the prostatic urethra, and to determine whether structural changes of the urethra within the prostate resulting from gland enlargement, rather than prostrate volume itself, lead to male lower urinary tract symptom (LUTS).

After standardizing measurements, 7 ultrasonography-determined variables, that is, prostate volume, transitional zone volume, transitional zone-to-total volume ratio, presence of intraprostatic protrusion, prostatic urethral angle, prostatic urethral length (PUL), and PUL-to-volume ratio (rPUL), were obtained prospectively in 293 men who had not taken LUTS medication during the 3 months prior to initial visits. Correlations between these variables and international prostate symptom scores (IPSS) were then investigated.

By simple correlation, only rPUL showed a significant association with IPSS. Multiple linear regression revealed IPSS were significantly correlated with age (beta = .179, P = .04) and rPUL (beta = .139, P = .019). Subanalysis with respect to the symptoms of IPSS revealed only rPUL was correlated with voiding symptoms (Q1,3,5,6; beta = .122, P = .036), and that age alone was correlated with storage symptoms (Q2,4,7; beta = .262, P < .001). When dividing 4 groups by applying mean cut-offs for PUL (62 mm) and prostate volume (30 g), long PUL with small volume had significantly higher IPSS score than short PUL with large volume (P = .042).

Structural differences of prostate related to prostatic urethra as reflected by rPUL were found to be significantly correlated with the severity of voiding symptoms. This finding suggests structural change of the prostatic urethra inducted by prostate enlargement underlies the development of male LUTS.