The Archdiocese of Chicago has reported that Cardinal Francis George underwent surgery earlier this week to remove cancerous cells in his kidney, as well as a nodule in his liver.

According to a brief statement Friday, doctors "will work with the Cardinal to plan a course of treatment," after the Aug. 15 procedure which took place at Chicago's Loyola University Medical Center.

The archdiocese said the 75-year-old cardinal will rest at home this weekend, will be on retreat next week and that it "has no further information at this time."

As leader of the archdiocese's 2.3 million Catholics since 1997, Cardinal George has also served as president of the U.S Conference of Catholic Bishops and is known for his strong pro-life views.

He submitted his letter of resignation to Pope Benedict XVI in January, as is customary for Church leaders upon reaching the age of 75. A Chicago native, he was ordained a priest in 1968.

Reuters reports that Cardinal George underwent surgery six years ago for bladder cancer.