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Background Initially kidneys were transplanted in uncomplicated patients, but nowadays patients with a large variety of comorbidities are referred for transplantation. Acceptance criteria for kidney transplantation are continuously being eased, but is there a limit? To what extent do increasing severity and number of comorbidities interfere with graft and patient survival?

Methods In our center, 1728 patients were transplanted between January 1, 2000 and December 31, 2012. Four pre-transplant comorbidity categories were defined: cardiovascular disease, peripheral vascular disease, cerebrovascular accident, and diabetes mellitus. Besides, a total comorbidity score was computed adding one point for each comorbidity category. Kaplan Meier analysis and various multivariable Cox proportional hazards analyses were performed to obtain survival curves and to test the independent influence of the comorbidity variables, corrected for variables with a known significant influence. Original disease was divided into diabetes mellitus and other.

Results There were 309 graft failures and 202 deaths in the period studied. Values of the total comorbidity point score were 0 (n=1057), 1 (n=459), 2 (n=157) and 3 (3 or 4 points, n=44). There were missing values in 11 cases. In Kaplan Meier analysis 5-year patient survival was 93% (score 0), 84% (score 1), 80% (score 2) and 68% (score 3) (p<0.001). The difference between the comorbidity scores was not significant for graft survival (p=0.97). In Cox analysis graft failure censored for death was significantly influenced by peripheral vascular disease (p=0.005) and by the known variables, e.g. donor type. In the separate Cox analysis the total comorbidity score did not have a significant influence on the risk of graft failure censored for death. Patient death was significantly influenced by cardiovascular disease (p<0.001). In the separate Cox analysis the total comorbidity score (p<0.001) had a significant influence on the risk of patient death. There was no interaction between donor type and comorbidity in these analyses.

Conclusion Graft survival is influenced by the presence of peripheral vascular disease, but not by the presence of other comorbidities analyzed. Patient survival on the other hand is influenced by the presence of comorbidities, but patient survival after transplantation in the population with comorbidity is very good. This means that even patients with comorbidities should be enabled to be selected for transplantation.