CHICAGO — Chicago Police Superintendent Eddie Johnson underwent a kidney transplant operation Wednesday that ended after several hours with officials expressing confidence about his recovery.

Police spokesman Anthony Guglielmi said Johnson was resting comfortably after the surgery at Rush University Medical Center. He added the superintendent and his son, who donated the kidney, got through the surgery without incident.

“Superintendent Johnson is in fair condition, vital signs are stable, he is conscious and comfortable and indicators are favorable,” the hospital said in a statement, adding Johnson’s 25-year-old son was in good condition.

When he arrived at the hospital early Wednesday, Johnson appeared calm and even joked with reporters about what might happen as a result of the operation. He said he hoped “I don’t get the urge to do the things that college kids do.”

Doctors expect Johnson to remain in the hospital for three to five days and then at home for three to six weeks.

Johnson over the last several days has seemed relaxed about the surgery. When he arrived at Rush University Medical Center early Wednesday he appeared calm and even joked with reporters about what might happen as a result of the operation.

“I just hope I don’t get the urge to do the things that college kids do,” Johnson said, smiling, alluding to his son, a graduate of Knox College.

Johnson expressed pride that his son had decided to donate one of his kidneys rather than have him remain on a waiting list for the organ.

“It’s a decision that he made on his own,” Johnson said. “It’s humbling. That’s not an easy thing, I’m sure, to make that decision.”

Johnson also talked about organ donation before he entered the hospital, saying he wanted to let people know they “can change somebody’s life” by donating.

Johnson disclosed his condition after a public dizzy spell in January. Though he later said the episode was not related to his condition he said he had battled the kidney ailment for several years. In recent months, he has continued to lose kidney function and his need for a new kidney became more urgent, prompting members of his police force and the public to offer to donate one of their kidneys.

Johnson never made it off the transplant list, and he recognized how fortunate he was that his son, Daniel, stepped forward, as he has continued to make public pleas for people to become organ donors.

On Wednesday, Illinois Secretary of State Jesse White, who has long been a champion for organ donation, praised Daniel Johnson as a “hero” for donating his kidney. In a statement, White said that in Illinois alone there are about 4,700 people waiting for a “lifesaving transplant,” with 300 people dying annually due to organ shortages.