The prelate earlier had experienced unstable blood pressure and a drop in his blood count despite having received blood transfusions, the report said. Surgeons had removed his bladder, prostate gland, part of his right ureter and several lymph nodes because of cancer.
The Roman Catholic Archdiocese of Chicago said in its Web site that the decision to operate Thursday was made after discussions with the cardinal.
Doctors at Loyola University Medical Center found that a small blood vessel in the pelvis was bleeding, the report said.
"The source was successfully closed, the bleeding was stopped, and the cardinal was stabilized," the statement said. "He tolerated the operation well and is resting comfortably this morning."
George had come through the original five-hour radical cystectomy well Thursday, the newspaper reported. However, it will be next week before a prognosis on his newly diagnosed cancer can be made, doctors told the newspaper.