Comparison of MR imaging and urodynamic findings in benign prostatic hyperplasia

In benign prostatic hyperplasia (BPH), it is uncertain whether the size of the prostate is related to the degree of urodynamically demonstrated bladder outlet obstruction. We compared MR imaging findings and urodynamic data in patients with surgically confirmed BPH.

We prospectively studied 43 benign prostatic hyperplasia (BPH) patients in whom transurethral resection of the prostate (TURP) was planned. We obtained T1- and T2-weighted images in the transverse and sagittal planes with a 1.5 Tesla superconducting unit. The predicted volume of the inner gland and the peripheral zone were obtained on T2-weighted transverse images. Prostatic protrusion into the urinary bladder (IB protrusion) and the inner gland ratio (IG ratio: inner gland volume/total prostatic volume) were determined.

IB protrusion and inner IG ratio were significantly greater in patients with severe stenosis than in those without. A surgical capsule (SC) was seen in 20 of 25 patients (80%) with severe stenosis and 8 of 18 (44%) of those without it. The accuracy of IB protrusion + IG ratio, IB protrusion + surgical capsule, and IB protrusion + IG ratio + surgical capsule was 89%, and that of IG ratio + surgical capsule was 86%.

The inner gland ratio, protrusion into the bladder, and presence of surgical capsule were the most important factors in bladder outlet obstruction. The probability of outlet stenosis increases in patients with more than two of these criteria.