The club say the 29-year-old Tigers vice-captain, who began experiencing pain on Monday evening and had surgery on Tuesday, is in danger of missing the rest of the season.
Gale, who could also be a major doubt for the World Cup, said: "I'm absolutely gutted to be facing surgery at this point in the season."
Gale, who was scrum-half in England's 30-10 win over Samoa in May, has played a key role in Castleford's historic season to date and broke the club's record for points in a season in last Friday's 38-24 win over Leeds.
The Tigers, who are 80 minutes away from a maiden Grand Final, have already won the league leaders' shield - for the first time in the club's 91-year history - and are favourites to go on and win the title.
Surgery went well... A few days rest and hopefully back to join the boys in no time! Thanks for all the messages I appreciate the love 🙌🏼— Luke Gale (@snozzer_gale) September 12, 2017
Gale added: "This is a freak situation that could happen to anyone at any time and it's just really unfortunate for me that it has happened to me now at such a crucial point in the season.
"Rest assured I'll be doing all I can to aid my recovery with an aim to getting back on the pitch as soon as possible. In the meantime I'll be 100% behind my team-mates in our quest for the Grand Final to top off what has already been a fantastic year."
Gale, who has amassed 338 points so far this year, has missed only two games in 2017. Paul McShane switched from hooker into the halves when he was away with England while back-up Tom Holmes, who is joining Featherstone at the end of the season, deputised for him when he was rested against St Helens in June.
However, Castleford head coach Daryl Powell remains hopeful that Gale could yet recover in time to play a part in his club's title bid.
He said: "Luke has had surgery relating to his appendix this afternoon which will keep him out of immediate action on the field.
"We are hoping for a speedy recovery back to the field before the end of the season."
Castleford have two league games left before their home semi-final on September 29 and the Grand Final is on October 7.
England are due to leave for the World Cup on October 15 and play their opening game against Australia in Melbourne on October 27.
Gale also missed only two games in 2016, when McShane again deputised, and Powell will be banking on his scrum-half showing similar powers of recovery to those of Salford hooker Malcolm Alker, who played just 15 days after having his appendix removed in 2004.
On the other hand, Hull full-back Shaun Briscoe pulled out of the 2005 Challenge Cup final in late August and did not play again that season.