WASHINGTON  —  Chief Justice William Rehnquist (search) was wheeled into the Capitol Medical Department on Monday, a reminder of the stakes of the filibuster fight being waged at the same time across the building in the Senate.

Rehnquist, 80, did not speak as he was led through the building by a security guard and trailed by another carrying his familiar wooden walking cane.

It was not immediately clear why Rehnquist went to the Capitol. Reporters' calls to officials at the Supreme Court (search) and the Medical Department were not immediately returned.

The chief justice has been treated for thyroid cancer and was absent from the bench between October and March, triggering speculation that he may announce his retirement at the end of the court's session next month. A vacancy would allow President Bush (search) to make his first appointment to the high court.

The Senate is immersed in a contentious battle over the Democrats' right to block some of the president's appointees to the federal appellate bench, but the fight is widely viewed as a precursor to an eventual party battle over a Supreme Court nominee.

After his visit to the Medical Department, located on the Capitol's first floor overlooking the site where Rehnquist administered the oath of office to Bush in January, aides pulled his limousine to a covered entrance below the House of Representatives.

The chief justice gingerly got out of the wheelchair to walk the final few steps to his vehicle.

The Supreme Court has two nurses on its staff but no physician. In the past, some justices have used the Capitol Medical Department, which is one long block away from the court.