A growing number of hospitals are opting to move some people from the emergency room into observation units where they can undergo further monitoring or testing before doctors decide whether they should be released or admitted. More than a third of hospitals report having such units today, a number that has doubled since 2003. But many hospitals and insurers haven't set up their clinical and billing systems or their insurance contracts with these patients in mind. Not only does this sometimes result in a longer stay at the hospital, it also can cause confusion for patients and bigger bills.