Let me spell it out for you Darwin, the procedure goes as follows:
1. Patient lies on left side, on the edge of the bed with his back to the doctor
2. Patient flexes right knee while extending left knee
3. Doctor explains to patient that (s)he is going to have to examine him by inserting his index finger into the anus
4. Doctor applies KY gel on index finger of right hand
5. Doctor is supposed to examine the external appearance of the anal region, feel for the anal sphincter tone, feel the mucosa of the rectum (just inside the anus) for any lumps, indurations
6. Doctor palpates the anterior wall of the rectum, where one can feel the prostate gland. (S)he attempts to estimate the size of the prostate (usually ~20gm/ should be able to feel beyond it's distal pole), feels the surface etc
This is probably why some people would prefer this to be done by a female doctor.
One laboratory investigation that can be done is to test for PSA (prostate specific antigen) which is a tumor marker BUT ONLY FOR SCREENING FOR PROSTATIC CANCER, IT WILL NOT SCREEN FOR BPH (benign prostatic hypertrophy) which is the cause for the majority of leaky bladders in men.
I hope this has helped.
PS Don't mind my name "injinia", if you have any health related queries just let me know.