In a statement posted on the senator's official Web site, Johnson was said to doing well following the operation at Avera McKennan Hospital in Sioux Falls, S.D. Johnson had been admitted Sunday with a possible reaction to an antibiotic with a fever.
"The surgery went exceedingly well," Johnson's surgeon, Dr. Donald J. Wingert, was quoted as saying in the statement. "We were able to remove the gallbladder laparoscopically. The senator is resting comfortably. All of our findings point to the gallbladder as the primary problem, but it is still possible that he is having some lingering effects from the antibiotic drug reaction.
"We will keep the senator in the hospital a few more days for observation."
Barb Johnson, the senator's wife, said he was in "good hands and in good spirits."
"We want to thank everyone for their prayers and support," she said.
The 63-year-old, three-term senator was treated for prostate cancer in 2004. In December 2006, he had surgery to drain blood from bleeding in his brain caused by a congenital problem and was hospitalized until late April 2007.
He was re-elected in 2008.