Length of stay is a metric hospitals and payers watch closely.  Typically, hospitals are reimbursed by the case, while physicians are reimbursed by the day.  In some instances, discharged patients have planned readmissions, but overwhelmingly, readmissions are unplanned-and in 2003-4, one fifth of nearly 12 million Medicare patients were rehospitalized within 30 days, and well over half, with medical and surgical conditions, were readmitted or died within one year.  A recent study estimated that rehospitalizations in 2004 cost Medicare $17.4 b.     MORE