To estimate the relationship between serum prostate-specific antigen (PSA) and prostatic epithelial volume, a new simple method for measuring epithelial volume was developed and its efficacy evaluated in patients with benign prostatic hyperplasia.

Between March 1998 and June 2001, 122 patients without prostate cancer in the transurethral resected specimen were enrolled in this study. Of the 122 patients, 55 had a serum PSA level of 4.0 ng/mL or greater and negative sextant biopsies before surgery. First, we measured the epithelium/glandular lumen ratio by computer image analysis in 20 specimens. Second, we measured the percentage of glandular lumen in all 122 patients. The prostatic epithelial volume was then calculated as follows: calculated epithelium volume (in cubic centimeters) = epithelium/glandular lumen ratio percentage of glandularlumen × total prostate volume (in cubic centimeters).

The epithelium/glandular lumen ratio was 1.01 in the 20 specimens. In the 122 patients with benign prostatic hyperplasia, the calculated epithelial volume correlated more strongly with the serum PSA level than did the total prostate volume, transition zone volume, or percentage of epithelium (γ = 0.672, P <0.0001). The mean PSA level per calculated epithelial volume was 1.27 ng/mL/cm³. The calculated epithelial volumes from the biopsy specimens correlated significantly with those from transurethral resection specimens (γ = 0.956, P <0.0001).

Serum PSA levels correlated significantly with prostatic epithelial volumes in patients with benign prostatic hyperplasia. The method of measuring prostatic epithelial volume used in this study is very convenient for clinical practice.