A prostatectomy is the surgical removal of all or part of the prostate gland. Abnormalities of the prostate, such as a tumour, or if the gland itself becomes enlarged for any reason, can restrict the normal flow of urine along the urethra.

Open Prostatectomy

A surgical procedure involving a skin incision and enucleation of the prostatic adenoma, through the prostatic capsule (RPP-retropubic prostatectomy) or through the bladder (SPP-suprapubic prostatectomy). Reserved for extremely large prostates.

From http://en.wikipedia.org/wiki/Prostatectomy