"Anytime you're operating on someone's penis, the most important thing is setting expectations ahead of time," said Niels V. Johnsen, M.D., a urologist at Vanderbilt University Medical Center in Nashville. "Because no matter what we do, you're not going to be 18 again."

Johnsen was referring to surgery to correct Peyronie's disease, a buildup of scar tissue inside the penis that causes curved erections. It's not unusual for men to have some curvature in an erect penis, but anything more than 30 degrees is reason to see a doctor, and 60 degrees off vertical is considered severe, said Petar Bajic, M.D., a member of the American Urological Association and a urologist at the Cleveland Clinic who specializes in Peyronie's.

Researchers don't know how many men may have Peyronie's disease, he added.

"It's still emerging research," Bajic said. "We know that it can have some genetic component, especially a similarity with