Disclosed is an apparatus and method for the treatment of the symptoms of obstructive prostatism. The apparatus comprises an expandable dilatation catheter and an axially elongate sheath, adapted for transurethral insertion via the external opening of the urethra. The sheath is ellipsoid in cross-section, and provides an initial path through which the catheter and a standard cystoscope lens is guided. Disposed near the proximal end of the expandable dilation portion of the catheter is a plurality of irrigation ports. A saline solution travels through an irrigation conduit and is secreted through the irrigation ports so as to flush away blood, etc., away from the lens of a cystoscope and provides the urologist with an unobstructed view of the dilation catheter and external urethral sphincter muscle. Once the catheter has been properly positioned with respect to both the bladder neck and the sphincter, the dilation balloon may be inflated to force open the affected prostatic urethra and eliminate the obstruction.