For years, researchers have known that black men have much higher rates of prostate cancer than do white men, and that black men are more than twice as likely to die from the disease as white men.

Now, another troubling racial disparity in prostate cancer has surfaced. For reasons that are unclear, black men also fare more poorly during and after prostate cancer surgery than do white men.

Researchers at Henry Ford Hospital in Detroit found four types of disparities in a database of patients who underwent radical prostatectomy, which removes the prostate and surrounding tissue:

• Black men more frequently needed blood transfusions during surgery (9 percent versus 6 percent in whites), a signal of trouble during surgery.

• In a related measure, 1.7 percent of black men had serious complications — such as hard-to-control bleeding — during surgery, compared to 1.3 percent of white men.

• After surgery, 13 percent of black men experienced complications such as infections and blood clots, compared to 10.3 percent of white men.

• Black men also had longer hospital stays, on average. Some 29 percent of black men stayed longer than three days after surgery, compared to 21 percent of white men.

But the death rate during those hospital stays was the same between whites and blacks.

The researcher heading the study, Quoc-Dien Trinh, said that it’s impossible to know at the moment why these differences exist. But he pointed to two possible factors that deserve follow-up study: differences in pelvic anatomy that make it more difficult to operate on blacks, and the possibility that prostate cancer in blacks tends to be more aggressive and therefore harder to operate on.

Trinh also said that overall quality of care for blacks tends to be lower than for whites, a troubling, persistent shortcoming of the U.S. health-care system.

“I’d say that it’s a little bit of everything – worse disease, presentation, anatomy that makes surgery harder,” Trinh said in a statement. “But it’s also a question of quality of care for ethnic minorities, especially in the American health-care system. And that needs to be raised.”

The study was presented this week at the annual meeting of the American Urological Association. It drew on a database of 7,408 African Americans and 51,319 white prostate cancer patients who underwent radical prostatectomy between 2001 and 2007.