Surgeons often are called glorified mechanics, and now it seems we have to question their honesty. Do you really need that engine work? Maybe not. But depending on the surgeon's profit motive, you might find yourself under the knife for an unnecessary overhaul.

Doctors financially invested in an outpatient surgical center perform twice as many surgeries than doctors with no such financial stake, according to a study published this month in Health Affairs by University of Michigan researchers.

The finding is alarming, the researchers said, because the number of these Medicare-certified facilities — sometimes called ambulatory surgery centers or surgicenters, specializing in relatively simple procedures such as knee, eye or ear surgeries — has increased by about 50 percent in the past decade. With more than 5,000 nationwide, they are 50 times more plentiful than specialty hospitals.

If surgeries there are motivated more by profit than need, this would have far-reaching ethical and financial implications, particularly for the newly enacted health care reforms.

Next, number 149?

Once viewed as a more convenient and personable alternative to a hospital, ambulatory surgery centers have become high-volume facilities, some serving more customers per day than a Jiffy Lube. Efficiency can be good in medicine, of course, if it is on the up-and-up.

Previous research from the University of Toronto found that, in 2005, physicians had a financial stake in over 80 percent of U.S. surgicenters and that over 40 percent were fully owned by physicians.

The new study, led by John Hollingsworth, a medical researcher at the University of Michigan in Ann Arbor, examined patients in Florida who underwent one of five common outpatient procedures: carpal tunnel release, cataract excision, colonoscopy, knee arthroscopy and a procedure to insert tubes in the ear. The researchers looked at which doctors were surgicenter owners and then compared their surgery zeal before and after they acquired ownership with doctors who remained non-owners.

The analysis revealed how doctors became high-volume surgeons only after they became facility owners, a clear conflict of interest.

Hollingsworth called this triple-dipping: collecting a professional fee for service, sharing in the facility's daily profits, and increasing the value of their investment in the facility. He said these surgeons might be lowering their thresholds for treating patients.

Health care loophole

All of this might be happening without Congress' knowledge. The Stark Law, dating back to the early 1990s, limits a physician's ability to self-refer patients to facilities where the physician has a financial stake. The law has weakened over the years, sometimes for practical reasons: Some doctors feel that their own hospital truly is the best place for a given procedure.

The focus in the recent health care debate has been on how to apply the Stark Law to specialty hospitals. Ambulatory surgery centers are exempt from the Stark Law largely because they are considered a less expensive alternative to specialty hospitals. But only a few such centers existed when the law was created; their numbers now dwarf that of specialty hospitals.

With the rapid growth rate of these centers, particularly in the past ten years, and the high potential for unnecessary procedures, it is time to question this exemption as well as a surgeon's profit motive.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears each Tuesday on LiveScience.