Does peritoneal dialysis for the kidneys break the fast of a fasting person, and is it permissible for my father to fast, knowing that fasting will not medically harm him, taking into consideration the introduction of water into the abdomen four times a day, or is he required to break his fast and offer expiation?

Peritoneal dialysis invalidates the fast because it involves the introduction of solutions that are absorbed by the stomach and nourish the body. If it is possible to postpone the dialysis until night without harm, then this must be done to preserve the fast. If it is not possible to postpone it due to necessity, then one may break the fast and make up for it later. If the illness persists and it is not possible to make up for the fast, then one must feed a poor person for each day.