Background: Patients with end-stage renal disease present comorbidities that increase mortality risk on the waitlist and after kidney transplantation. This study aimed to determine the impact of baseline comorbidities on the risk of death after kidney transplantation compared to remaining on the waitlist.

Methods: Records of waitlisted patients were retrospectively analyzed. Multivariable time-dependent Cox-regression model was used to determine the initial and the lowest relative hazard-risk of death (HRD) after exposure to kidney transplantation.

Results: 1692 patients were included in the study. Patients without comorbidities had the relative HRD 3-fold higher, immediately after kidney transplantation, but it reduced progressively, reaching equality to waitlist at 75 days and a HRD of 0.28 thereafter (p<0.001). Patients with Diabetes and coronary artery disease had an initial relative HRD of 2.41 (p=0.009) and 2.68 (p=0.009) and matched to the waitlist at 175 and 200 days, respectively. Patients with peripheral vascular disease, had an initial relative HRD 3.6-fold in the first 240 days (p=0.008) and patients with congestive heart failure a relative HRD of 7.47 (p=0.07). Both declined rapidly, reaching equality at 110 days. Finally, all comorbidities, except cerebrovascular disease, presented lower HRD on long-term follow-up.

Conclusions: This study shows that the time and the range of relative HRD between kidney transplantation and waitlist varies depending upon the patients´ baseline comorbidities.

We retrospectively analyzed the records of all patients waitlisted for the first kidney transplantation with deceased donors in our electronic database between January 1^st, 2007 to December 31^st, 2012.

Before listing, patients were evaluated following established international guidelines [22-25]. Patients older than 50 years with previous cardiovascular events and those with diabetes were evaluated with invasive coronary angiography, with intervention when necessary [26-30].

Patients were followed from the date of listing through the date of death or July 31st, 2015. Patients who lost their follow-up were contacted by phone to report kidney transplant in another center or a report, from a relative, of death on the waitlist at any time of follow-up.

Patients with inactive waitlist status at any time of follow-up were not censored at the time of de-listing, because these patients were inactivated for bureaucratic reasons (lack of blood sample collection periodically, requirement of Brazil allocation system) and not for clinical indication. Once they fulfilled the requirements they returned as active on the waitlist.

Transplanted patients with primary non-function (PNF), defined as permanent absence of kidney function posttransplant [31], or graft loss were censored at the time of return to dialysis treatment.

Exclusion criteria were age under 18 years, previous transplant with another solid organ and listed for combined organ transplant. Eighteen patients were also excluded because their final waitlist status could not be determined.