Is it permissible for someone who has undergone surgery to remove a part of the ureter and is experiencing kidney pain to break their fast, given that they are unable to make up for the days they miss?

A sick person for whom fasting is harmful and difficult is permitted to break their fast. This can be known through experience or by the reliable physician's advice. Whoever breaks their fast must make up for the missed days on other days when fasting is not difficult for them. If they are permanently unable to make up for the missed days, then they must feed a poor person for each day they broke their fast, based on the Almighty's saying: ﴿And upon those who are able to fast, but with difficulty - a ransom [as substitute] of feeding a poor person for every day.﴾