Selecting appropriate controls for kidney donors--reply

Long-term Mortality Risks Among Living Kidney Donors in Korea

RATIONALE & OBJECTIVE

Living kidney donors may have a higher risk for death and kidney failure. This study aimed to investigate the long-term mortality experience of living kidney donors compared with members of the general public in Korea who underwent voluntary health examinations.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

We first calculated standardized mortality ratios for 1,292 Korean living kidney donors who underwent donor nephrectomy between 1982 and 2016 and 72,286 individuals who underwent voluntary health examinations between 1995 and 2016. Next we compared survival between the 1,292 living kidney donors and a subgroup of the health examination population (n=33,805) who had no evident contraindications to living kidney donation at the time of their examinations. Last, a matched comparator group was created from the health examination population without apparent contraindication to donation by matching 4,387 of them to donors (n=1,237) on age, sex, body mass index, estimated glomerular filtration rate, urine dipstick albumin excretion, previously diagnosed hypertension and diabetes, and era.

EXPOSURES

Donor nephrectomy.

OUTCOMES

All-cause mortality and other clinical outcomes after kidney donation.

ANALYTICAL APPROACH

First, standardized mortality ratios were calculated separately for living kidney donors and the health examination population standardized to the general population. Second, we used Cox regression analysis to compare mortality between living kidney donors versus the subgroup of the health examination population without evident donation contraindications. Third, we used Cox regression analysis to compare mortality between living kidney donors and matched comparators from the health examination population without apparent contraindication to donation.

RESULTS

The living kidney donors and health examination population had excellent survival rates compared with the general population. 52 (4.0%) of 1,292 kidney donors died during a mean follow-up of 12.3±8.1 years and 1,072 (3.2%) of 33,805 in the health examiner subgroup without donation contraindications died during a mean follow-up of 11.4±6.1 years. Donor nephrectomy did not elevate the hazard for mortality after multivariable adjustment in kidney donors and the 33,805 comparators (adjusted HR, 1.01; 95% CI, 0.71-1.44; P=0.9). Moreover, living donors showed a similar mortality rate compared with the group of matched healthy comparators.

LIMITATIONS

Donors from a single transplantation center. Residual confounding owing to the observational study design.

CONCLUSIONS

Kidney donors experienced long-term rates of death comparable to nondonor comparators with similar health status.

Incidence of Cardiovascular Events after Nephrectomy - A Single Centre, Matched Pair Analysis between Donor and Tumour Nephrectomy in a Long Term Follow-Up

INTRODUCTION

The study aimed to compare the incidence of cardiovascular events (CVEs) after donor nephrectomy (DN) and radical tumor nephrectomy (RN), according to an estimated glomerular filtration rate (eGFR), were evaluated over time.

MATERIALS AND METHODS

Follow-up was collected for DN who underwent surgery from 1998 to 2007 for CVE and renal function. All DN were matched for age to patients treated by RN or adenoma enucleation (control group), who were eligible for DN. eGFR was estimated using the Cockgroft-Gould formula. Patients with preoperative comorbidities were excluded.

RESULTS

Thirty DN (median age 48.9 years) were included with a median follow-up of 138.5 months (interquartile range 119-159). No significant differences in patients' characteristics were found preoperatively (p > 0.5). Four out of 30 DN developed a CVE (3 myocardial infarctions (MI), 1 stroke), 2 of 30 patients in the control group (both MI) and 8 of 30 RN patients (6 MI, 2 strokes, p > 0.05). Arterial hypertension developed in 14 DN (46.7%), in 12 (40%) after RN and in 15 controls. The CVE occurred after a median time of 68 months (5-231) and were related to a drop of ∼30% in the eGFR irrespective of the group.

CONCLUSION

Decline of renal function after nephrectomy is the main risk factor for CVE. Close monitoring of renal function and new onset hypertension is warranted.

Long-Term Structural and Functional Myocardial Adaptations in Healthy Living Kidney Donors: A Pilot Study

BACKGROUND AND AIMS

Compensatory renal hypertrophy following unilateral nephrectomy (UNX) occurs in the remaining kidney. However, the long-term cardiac adaptive process to UNX remains poorly defined in humans. Our goal was to characterize myocardial structure and function in living kidney donors (LKDs), approximately 12 years after UNX.

METHODS AND RESULTS

Cardiac function and structure in 15 Italian LKDs, at least 5 years after UNX (median time from donation = 8.4 years) was investigated and compared to those of age and sex matched U.S. citizens healthy controls (n = 15). Standard and speckle tracking echocardiography (STE) was performed in both LKDs and controls. Plasma angiotensin II, aldosterone, atrial natriuretic peptide (ANP), N terminus pro B-type natriuretic peptide (NT-proBNP), cyclic guanylyl monophosphate (cGMP), and amino-terminal peptide of procollagen III (PIIINP) were also collected. Median follow-up was 11.9 years. In LKDs, LV geometry and function by STE were similar to controls, wall thickness and volumes were within normal limits also by CMR. In LKDs, CMR was negative for myocardial fibrosis, but apical rotation and LV torsion obtained by STE were impaired as compared to controls (21.4 ± 7.8 vs 32.7 ± 8.9 degrees, p = 0.04). Serum creatinine and PIIINP levels were increased [1.1 (0.9-1.3) mg/dL, and 5.8 (5.4-7.6)] μg/L, respectively), while urinary cGMP was reduced [270 (250-355) vs 581 (437-698) pmol/mL] in LKDs. No LKD developed cardiovascular or renal events during follow-up.

CONCLUSIONS

Long-term kidney donors have no apparent structural myocardial abnormalities as assessed by contrast enhanced CMR. However, myocardial deformation of the apical segments, as well as apical rotation, and LV torsion are reduced. The concomitant increase in circulating PIIINP level is suggestive of fibrosis. Further studies, focused on US and EU patients are warranted to evaluate whether these early functional modifications will progress to a more compromised cardiac function and structure at a later time.