Third baseman Bill Hall, who was optioned to Triple-A Nashville last week, was recalled.
Hart complained of stomach and side pains Saturday night after he went 0 for 3 in the Brewers' 4-2 loss to San Diego. He missed Milwaukee's 6-1 victory on Sunday as the pain persisted. He underwent an appendectomy that night.
"The medical people in San Diego were terrific," Brewers manager Ken Macha said before Monday night's game against the Los Angeles Dodgers. "To get that all scheduled and done on a Sunday was pretty awesome, so thanks to those people for the work they did. The good part of that is they got it before it burst or anything like that."
Monday's trip to the disabled list is the first for Hart, who is batting .264 with 11 homers and 40 RBIs in 98 games.
"I think he's still in the hospital, and our medical people want to get him back to Milwaukee as soon as they can," Macha said. "They're concerned, I guess, about infection or something like that when they do this procedure, so they would like to make sure they can keep as close an eye on it as possible."
Hall returned four days after being optioned to the minors. In 71 games with the Brewers, he is batting .201 with five homers and 20 RBIs.