Bjorn Thorbjarnarson, a New York surgeon who famously treated the shah of Iran and Andy Warhol before becoming a central figure in a widely publicized lawsuit over Warhol’s death after surgery in 1987, died on Oct. 4 in Warren, N.J. He was 98 .

The death, at a care facility, was confirmed by his daughter Lisa Enslow .

Dr. Thorbjarnarson was one of the foremost experts on surgeries of the biliary tract — involving the liver, gall bladder and bile ducts — when he was called to remove Warhol’s infected gallbladder in 1987 at New York Hospital-Cornell Medical Center, where he worked for virtually his entire career. (Ms. Enslow said he had treated other famous patients as well, including Johnny Carson, the physicist J. Robert Oppenheimer and the artist Ellsworth Kelly.)

Dr. Thorbjarnarson (who pronounced his surname thor-bee-ON-a-son so that it would be easier for his American colleagues to master) completed the operation on Warhol without incident, and Warhol seemed stable as he recovered in a private hospital room. But his condition deteriorated overnight, and he died in the early hours of Feb. 22 at 58. At the time, many newspapers characterized the operation as “routine.”

That April, the New York State Health Department released a report concluding that Warhol’s treatment had been inadequate. The Manhattan district attorney’s office soon mounted an investigation, but it found insufficient evidence to bring criminal charges.