Recall that CIC looks at possibility of medical excessive demand for a period of up to 10 years after the applicant would land as a PR. So even if the applicant's current situation is stable, CIC doctors may feel he would need more treatments (in this case dialysis) at some point during his first 10 years in Canada (so any age up to 85), which would then exceed the excessive demand criteria.
http://www.cic.gc.ca/english/resources/tools/medic/admiss/excessive.asp
a demand on health services or social services for which the anticipated costs would likely exceed average Canadian per capita health services and social services costs over a period of five consecutive years immediately following the most recent medical examination required under paragraph 16(2)(b) of the Immigration and Refugee Protection Act (IRPA), unless there is evidence that significant costs are likely to be incurred beyond that period, in which case the period is no more than 10 consecutive years;