"It's something that was affecting his play," Reds general manager Walt Jocketty said.
Votto left Friday night's game against Milwaukee after missing 12 starts and leaving two other games early during a 17-game stretch this month. He was expected to head back to Cincinnati, and Jocketty said the timeline for his return was unclear.
Votto ranks among the NL leaders with a .357 batting average. He has eight home runs and 33 RBIs.
The Reds did get some good news Saturday, when second baseman Brandon Phillips returned to the lineup, batting cleanup. Phillips hadn't started since last Saturday because of a hairline fracture on the tip of his right thumb.