What about the ritual ablution (wudu') and prayer (salat) for a patient with kidney failure?

If a person afflicted by illness is unable to perform purification and prayer, they must do what they can without harm. They should purify themselves with water; if unable, they may seek assistance from others; if no water is found, they should perform tayammum and pray. If they cannot do that, they should pray without ablution or tayammum. They should pray standing if able; otherwise, sitting, or on their side, or lying down. Prayer is not waived for a mature Muslim unless they lose their sanity. Some scholars, including Ibn Taymiyyah, held the view that prayer is waived for those who cannot even gesture with their head, heart, or eyes. The basis for this is Allah’s saying: "So fear Allah as much as you are able" and "Allah does not charge a soul except [with that within] its capacity," and the Prophet's (PBUH) saying: "When I command you to do something, do as much of it as you can."