New concept of BPH: PCAR theory.

Abstract

A new concept of the pathophysiology of benign prostatic hyperplasia (BPH), based upon the presumed circle area ratio (PCAR) theory, is described. The PCAR is the ratio of the area of the maximum horizontal section of the prostate by transrectal sonography to the area of a presumed circle of which the circumference is equal to the circumference of the maximum horizontal section. This evaluates how closely the shape of the section approaches a circle. A clear borderline was found at a PCAR of 0.75 in the postvoiding residual urine volume (PVR) in many cases of BPH. Cases with the PCAR below this level almost entirely showed a PVR below 30 ml, while cases with the PCAR over this level demonstrated a wide distribution of PVR. Such a variety of PVR in cases with the PCAR over 0.75 could be explained by the difference of the elasticity of the surgical capsule (peripheral zone) in each case, which was confirmed by a stress-strain test on extirpated specimens from the capsule at surgery. We developed a new clinical parameter called the prostatic pressure coefficient (PPC) to check elasticity, by means of a special balloon catheter inserted into the prostatic urethra.