From Medpundit:

"A patient is seen and treated in the office. The doctor submits the bill to the insurance company, which, according to the contract it has with the doctor, is supposed to pay the bill within a certain number of days, say 30. On the thirtieth day the doctor doesn't get a payment. Instead he gets a form from the insurance company claiming they need more information about the visit. Was it for a pre-existing a condition? To make it even more difficult, the letter doesn't specify which diagnosis for that visit it has concerns about, and sometimes it doesn't even state the day of service. So, if a patient saw the doctor for two things – say an ear infection and to have his blood pressure medicine renewed, or if he's been to the office twice for two separate problems, the doctor's staff has to call to clarify things, a process which can take minutes to days. Then, the form has to be mailed back to the insurance company. They won019t accept the information by phone. This happens even if the condition is clearly not a pre-existing one. In fact, I see it most frequently for office visits that have been for an acute problem such as an ankle sprain or an ear infection. The only reason the insurance company has for doing this is to delay payment by another couple of months."

ugh.  This is my life.  Well put, "medpundit."