The federal Centers of Medicare & Medicaid Services on Wednesday published guidance that may allow Center City's Wills Eye Hospital to regain its status as a hospital under Medicare rules, a key to the organization's financial health.

Wills lost its hospital status in October when a federal appeals board upheld a decision that Wills served too few inpatients in a four-bed unit at its facility at Ninth and Walnut Streets to qualify as a hospital.

The new guidance, advocated for by the region's congressional delegation, does not appear to create an easy path for Wills to be recertified as a hospital for Medicare purposes, but it does say that "hospitals are not required to have a specific inpatient-to-outpatient ratio" to meet the criteria as a hospital.

When evaluating Wills' application for hospital status in 2013, a federal official in CMS's Philadelphia office decided that Wills had an inpatient-to-outpatient ratio of just 17 percent. Such a specific calculation has been taken off the table.

Wills said it was reviewing the new guidance.