The condition for which Senator John McCain had surgery on Friday may be more serious than initial descriptions have implied, and it may delay his return to Washington by at least a week or two, medical experts said on Sunday.

The Senate majority leader, Mitch McConnell, has already announced that votes on a bill to dismantle the Affordable Care Act will not begin until Mr. McCain’s return. A statement released by Mr. McCain’s office on Saturday had suggested that he would be in Arizona recovering for just this week, but neurosurgeons interviewed said the typical recovery period could be longer.

The statement from Mr. McCain’s office said a two-inch blood clot was removed from “above his left eye” during a “minimally invasive craniotomy with an eyebrow incision” at the Mayo Clinic Hospital in Phoenix, “following a routine annual physical.” Surgeons there are not conducting interviews. Mr. McCain’s communications director, Julie Tarallo, said further information would be made public when it became available.

A craniotomy is an opening of the skull, and an eyebrow incision would be used to reach a clot in or near the left frontal lobes of the brain, neurosurgeons who were not involved in Mr. McCain’s care said.