Each year, insurers refuse to pay at least $50 billion worth of medical bills. Some areas where disputes often arise:

Nursing care for disabled patients is a frequent bone of contention, since a full-time home nurse costs at least $73,000 a year, according to a survey by MetLife. But doing without can be costly, too. Parents can push food through a feeding tube, argues Beth Dworetzky, of the Federation for Children with Special Needs, but they might not realize when there s an infection.

Medical equipment

Many insurance policies cap the amount of money that can be spent each year per person on medical equipment like wheelchairs, canes and ventilation machines. Other companies might pay for, say, a $20,000 wheelchair but refuse to pay for spare parts, batteries or maintenance. Pretty insane, says Karen Mariner, of the National Multiple Sclerosis Society.

Prescription drugs

Insurers balk at off-label prescriptions that use drugs in ways not approved by the Food and Drug Administration. Some breast-cancer patients taking tumor-slowing drug Avastin, for instance, had to pay as much as $85,000 annually for the medication before it gained approval for their disease last year; those with rare, less-studied conditions face the issue often.

Rehabilitative therapy

Insurers and patients frequently tussle over appropriate care after injury or stroke. But the fiercest debates center on services for someone who never had certain skills or won t fully recover them like developmentally delayed children or patients with degenerative conditions like Huntington s disease. Stays in some inpatient facilities can top $15,000 per stint.