(REUTERS HEALTH) - Men with sexual dysfunction after prostate cancer surgery are often surprised to learn that the surgery had put them at risk for those problems, a new study finds.

The men in the study had come to a sexual health clinic because of problems they were having after removal of a cancerous prostate gland. Researchers who quizzed them about the sexual function information they had received preoperatively found that the men had "largely unrealistic expectations" about their sexual health after the surgery, like whether they'd be able to achieve erections.

"I think this data is some of the first to report what we see in the clinic," said Dr. Joshua Meeks, a urologist affiliated with the Northwestern University Feinberg School of Medicine in Chicago.

Men with prostate cancer have several treatment options, which include active surveillance, radiation and removing the gland altogether. All have potential side effects, according to senior study author Dr. John P. Mullhall and colleagues at Memorial Sloan Kettering Cancer Center in New York City.

As reported in BJU International, Mulhall and colleagues surveyed 336 men with sexual dysfunction roughly three months after a prostate removal operation known as a radical prostatectomy. About two-thirds of the group had traditional open surgery; the rest had robotic-assisted surgery.

The average age was 64. Most of the men--about 88 percent of open surgery and 91 percent of robotic surgery patients--said they'd been able to have sex before surgery.

But only 38 percent knew whether they'd had nerve sparing surgery, which helps preserves sexual function. And only half of the patients realized the surgery would take away their ability to ejaculate.

Less than 10 percent knew their penis length might decrease after surgery.

Few men in either group were aware of the potential for changes in orgasms and pain or incontinence during orgasms.

The study didn't analyze the information patients received from their doctors before the surgery, so the researchers can't distinguish between what patients were told and what they remembered.

Still, the results show that some men may not retain information from their doctor about the risks of prostate removal, said Meeks, who was not involved with the new study.

"I think it really highlights why it’s important to have their spouse there, because I think having another set of ears is incredibly helpful," he told Reuters Health.

Dr. Daniel Shoskes, a urologist at the Cleveland Clinic who also wasn't involved in the study, told Reuters Health the conclusions fit with what his team has known for some time.

In fact, the Cleveland Clinic has started a half-day class for men undergoing prostate removal to educate them about the surgery and rehabilitation. The hope, said Shoskes, is that the classes will "have an impact on patient retention and satisfaction with the surgery."

Shoskes, who also was not involved with the new research, added, "It is human and normal to forget what has been told to you. In some cases, it's the surgeon that needs to do a better job" delivering the information.

The study's lead author did not respond to a request for comment. In their paper, however, the study team also emphasizes the need to better prepare men for these operations. The study findings, they write, "should give us reason to think about our approach to the education of the patient prior to radical prostatectomy."

Patients "are not remembering or appreciating the information the way that it is intended" and undertake the operation with mistaken expectations regarding their sexual health, they add.