The Japan international is recovering from a serious ankle injury suffered in February.
Endo's hopes of making Japan's World Cup squad is now under threat, though he is working towards making a return for Liverpool before the season concludes.
He said on Kodinsha's Red Machine podcast: "It was a ligament injury, one that connects one bone to another, and it had completely gone.
"Then I decided to fix it. I had two options, to put a plate in the my foot to connect one bone to another, and then another two so four bones had to be connected.
"The second was to put an artificial ligament and I have chosen the second one. It's easier to have because if I had a plate I'd have had to take it out after three months.
"The doctor in the UK said if I played with the plate in the World Cup, then maybe after World Cup I'd need to take it out and then I'd have another three months out. This artificial ligament only takes three months.
"I decided to do the surgery in Japan. I was thinking if I want to play in the World Cup, it would be the best for me.
"I'm hoping to play in the World Cup. My target is the last weekend of May - the national team has a game then (against Iceland on May 31) or we have a Champions League final! I hope we can make it. At least I have something to achieve - I'm motivated by that."