Is it obligatory to make up eight years of fasting or to feed the poor for one who broke their fast due to kidney stones that were treated years later, given the inability to fast consecutive days?

If you have recovered from an illness and your doctor informs you that fasting will not affect you, then you are obligated to make up the missed fasts (qada'), and you can do so intermittently according to your ability. This is because feeding the poor (it'am) does not substitute for fasting except in the case of a chronic illness. However, if fasting would affect you and cause unbearable hardship, then you must feed one poor person for each day (you missed). The amount to feed is one mudd of food (approximately 750 grams of rice or what is considered the staple food of the people of the land).