In the first effort of its kind, the nonprofit publisher of Consumer Reports magazine released ratings of 2,463 U.S. hospitals in all 50 states on Wednesday, based on the quality of surgical care. The group used two measures: the percentage of Medicare patients who died in the hospital during or after their surgery, and the percentage who stayed in the hospital longer than expected based on standards of care for their condition. Both are indicators of complications and overall quality of care, said Dr John Santa, medical director of Consumer Reports Health.

According to the story in Reuters Health, the ratings will surely ignite debate, especially since many nationally renowned hospitals earned only mediocre ratings. The Cleveland Clinic, some Mayo Clinic hospitals in Minnesota, and Johns Hopkins Hospital in Baltimore, for instance, rated no better than midway between “better” and “worse” on the CU scale, worse than many small hospitals. Because CU had only limited access to data, the ratings also underline the difficulty patients have finding objective information on the quality of care at a given facility.

Nevertheless, “this is a step in the right direction,” said Paul Levy, former president of Beth Israel Deaconess Medical Center in Boston, who was not involved in the project. “To whatever extent you can empower patients to get better care and become partners in pushing the healthcare system to make improvements is to the good.”

CU’s ratings are based on Medicare claims and clinical records data from 2009 to 2011 for 86 kinds of surgery, including back operations, knee and hip replacements, and angioplasty. The rates are adjusted to account for the fact that some hospitals treat older or sicker patients, and exclude data on patients who were transferred from other hospitals. These are often difficult cases that, CU felt, should not be counted against the receiving hospital.

Although the ratings do not explicitly incorporate complications such as infections, heart attacks, strokes, or other problems after surgery, the length-of-stay data captures those problems, said Santa.

Some of the findings are counterintuitive. Many teaching hospitals, widely regarded as pinnacles of excellence and usually found at the top of rankings like those of U.S. News and World Report, fell in the middle of the pack.

“This isn’t the first time we’ve seen this sort of surprise,” said Dr Marty Makary, a surgeon at Johns Hopkins Hospital and author of the 2012 book, “Unaccountable: What Hospitals Won’t Tell You and How Transparency Can Revolutionize Health Care.” “For a complex procedure you’re probably better off at a well-known academic hospital, but for many common operations less-known, smaller hospitals have mastered the procedures and may do even better” with post-surgical care.

CU also found that several urban hospitals did well despite serving many poorer, sicker patients, including Mount Sinai Hospital in New York and University Hospitals Case Medical Center in Cleveland. Rural hospitals did better, on average, than other hospitals, and many hospitals practically unknown beyond their zip code outranked famous ones, including Kenmore Mercy near Buffalo, New York; Arrowhead in Glendale, Arizona; Sacramento Medical Center in California; and Arkansas Heart in Little Rock.