NPB commissioner Ryozo Kato had an operation to remove gallstones today. According to the NPB, Kato hadn't been feeling well since the end of the last year and found out in mid-March that he had gallstones.
Kato is expected to be released from the hospital in a couple of days and will continue to receive treatment after that.
UPDATE 6/1 @ 6:24pm - Kato was discharged from the hospital today and will spend the next few days getting rest at home. He is expected back at the office early next week.