Bayern Munich striker Eric Maxim Choupo-Moting said late Thursday he underwent kidney stone surgery last week and hopes to be back in action soon. “Last week I had a surgery. They had to remove a kidney-stone. The surgery went well and I am already under construction-training to get back on track asap,” the 33-year-old said on Instagram. Bayern had previously only said that Choupo-Moting was absent from training without giving a reason. It is not known when he can return to team training. Bayern open the Bundesliga season later Friday at Europa League champions Eintracht Frankfurt.