To evaluate the relationship between the lengths of 2 regions of the intraprostatic urethral sphincter, the distal region (from the apex to the adenoma [AA]) and the proximal region (from the adenoma to the verumontanum [AV]) and prostate volume (PV) in patients with clinical benign prostate hyperplasia.

A total of 110 patients who underwent magnetic resonance imaging before holmium laser enucleation of the prostate were enrolled. The lengths of 2 distinct intraprostatic urethral regions were measured on magnetic resonance imaging, and we used multiple regression analysis to explore the association between these lengths and PV.

The median age was 69 years. The median AV and AA lengths were 6.0 and 5.7 mm, respectively. Multiple regression analysis to predict PV revealed that the interaction between age and AV length was significant (P = .012), whereas that between age and AA length was not (P = .819). In patients aged ≥69 years, the AV length was significantly positively associated with the PV (P = .005); in patients aged ≤69 years, a nonsignificant positive association was observed (P = .130). The AA length was not associated with the PV in either subgroup (P = .621 in those aged <69 years and P = .189 in those aged ≥69 years).

Our results may indicate that the proximal length, which is covered by the adenoma, becomes longer as prostate hyperplasia progresses, whereas the distal length does not. It may be important to preserve the intraprostatic length of the striated sphincter when the urethra is dissected at the apex during radical prostatectomy.