Fig. 1

MRI measurements. a is the MUL. MUL was measured as the distance of the apex of the prostate to the base of the bulbous urethra. b is the MUW. MUW was defined as the maximum diameter of the membranous urethra. LT was calculated as (c − d)/2. c stands for the outer levator distance and d stands for the inner levator distance. PV was calculated as e × f × g × π/6/1000. e is the maximum height of the prostate, f is the maximal prostate width and g is the maximal prostate length. Intravesical prostatic protrusion [h (mm)], which is measured from the tip of the protruding prostate to the base of the bladder (mid-sagittal T2-weighted image)