BIDDEFORD — Dr. John M. Walker, a prominent surgeon and uncle of President Bush, died Thursday at a hospital here, about 20 minutes before Bush arrived on short notice for an early morning visit.

Walker, the brother of Bush’s 89-year-old mother, Dorothy Walker Bush, formerly served on the staff at Memorial Sloan-Kettering Cancer Center in New York City.

Walker, 81, lived in Easton, Md., and was a summer resident of Kennebunkport. His survivors include his wife, Louise, three sons, three daughters, two brothers and two sisters.

No immediate details were available on the cause of death.

Bush left for Southern Maine Medical Center from his Walker’s Point home in Kennebunkport, a 10-mile trip.

A supervisor at the Biddeford hospital, Shirley Bowman, said, “Dr. John Walker did expire at 6:41 this morning,” about 20 minutes before Bush arrived. She would provide no other details.

Walker served on the staff at Memorial Sloan-Kettering from 1952 to 1959, said Maureen Montone, a spokeswoman at the New York hospital.