The surgery on Don Hayden's son was successful. The only lingering complication: a bill for $23,000.

The Gaithersburg family, surprised that insurance didn't cover the cost, spent about a year fighting the charge from the medical clinic — even after it was reduced to $16,000.

The clinic turned the bill over to a collection agency, and the Haydens prepared to hire a lawyer.

That's when an administrative worker at the clinic advised the family in a whisper to contact Maryland's Health Education and Advocacy Unit, which mediates such disputes on behalf of consumers.

Investigators from the advocacy unit looked into the charge and found that the clinic had failed to submit claims in time to be paid by the insurer and so billed the patient instead. When the advocacy unit pointed out the error, the clinic agreed to forgive the bill.

The advocacy unit, Hayden says, is "probably the best-kept secret in town."

Indeed, many Marylanders are unfamiliar with this unit that is part of the Consumer Protection Division in the Maryland attorney general's office. But it's a resource to remember, particularly if you're confused by medical bills — who isn't? — or if your insurer always seems too quick to say no.

The advocacy unit assisted more than 1,900 consumers last year, recovering more than $1.2 million for them.

There are private companies that verify billing accuracy and negotiate medical bills on a patient's behalf, but they keep a percentage of the savings. The state's service is free.

Most states now have similar consumer-assistance programs, but Maryland's unit is one of the oldest and, some health specialists say, a model for others.

"They have a real solid history of success in helping consumers when their plan denies a service," says Cheryl Fish-Parcham, deputy director of health policy at the nonprofit Families USA.

When the Health Education and Advocacy Unit was established in 1986, its mission was to educate consumers and help them resolve disputes involving health care bills and medical equipment. In the late 1990s, it started assisting consumers as they challenged denials of coverage before insurance companies' appeals boards.

Now, thanks to the federal health care overhaul, the program is preparing for a heavier caseload.

"There is an expectation that when [the overhaul] goes into effect in 2014, that there will be 180,000 additional Marylanders insured," says Kim Cammarata, the unit's director. "Which means that there will be 180,000 additional Marylanders that may need assistance with insurance appeals."

The federal government gave the state a $642,000 grant last year to help with the extra work. Part of the money was used to hire two ombudsmen to handle appeals, for a total of five, and an outreach coordinator.

The unit aims to hire other staff, too, though managers will have to stretch those dollars. Unless more federal money is made available, Cammarata says, the grant will run out by the time the health care law takes full effect — and these added positions could disappear.

About 20 percent of the complaints the unit handled last year involved billing disputes. Sixty-three percent of those were resolved in the consumer's favor.

Most of the rest of the complaints were appeals of insurers' decisions to deny coverage of treatments that the companies deemed medically unnecessary, experimental or outside the contract.

The unit says it succeeded in getting 65 percent of the contract denials and 54 percent of the medical necessity denials overturned or modified last year.