Invited response to "Hyperfiltration After Donation and Living Kidney Donor Risk"

Association Between Living Kidney Donor Postdonation Hypertension and Recipient Graft Failure

BACKGROUND

Recipients of kidneys from living donors who subsequently develop end-stage renal disease (ESRD) also have higher graft failure, suggesting the 2 donor kidneys share risk factors that could inform recipient outcomes. Given that donor ESRD is rare, an earlier and more common postdonation outcome could serve as a surrogate to individualize counseling and management for recipients. Hypertension is a frequent event before donor ESRD; thus, early postdonation hypertension might indicate higher risk of graft failure.

METHODS

We studied Scientific Registry of Transplant Recipients data to quantify the association between early postdonation hypertension and recipient graft failure using propensity score-weighted Cox proportional hazards regression. We also examined the association between postdonation systolic blood pressure and graft failure.

RESULTS

Of 37 901 recipients, 2.4% had a donor who developed hypertension within 2 years postdonation. Controlling for donor and recipient characteristics, recipients whose donors developed hypertension had no higher risk for graft failure (adjusted hazard ratio [aHR] 1.03, 95% confidence interval [CI] 0.85-1.25, P = 0.72). This was consistent among subgroups of recipients at higher risk for adverse outcomes due to hyperfiltration: African American recipients (aHR 1.10, 95% CI 0.70-1.73, P = 0.68) and those with ESRD caused by hypertension (aHR 1.10, 95% CI 0.65-1.85, P = 0.73) or diabetes (aHR 0.80, 95% CI 0.56-1.13, P = 0.20). However, graft failure was associated with postdonation systolic blood pressure (per 10 mm Hg, aHR 1.05, 95% CI 1.03-1.08, P < 0.001).

CONCLUSIONS

Although postdonation systolic blood pressure is associated with graft failure, the reported diagnosis of hypertension as determined by the requirement for blood pressure treatment early postdonation did not portend a higher risk of recipient graft failure in the same way as eventual postdonation ESRD.

Estimated glomerular filtration rate for longitudinal follow-up of living kidney donors

Background

Living kidney donor safety requires reliable long-term follow-up of renal function after donation. The current study aimed to define the precision and accuracy of post-donation estimated glomerular filtration rate (eGFR) slopes compared with measured GFR (mGFR) slopes.

Methods

In 349 donors (age 51 ± 10, 54% female), we analysed eGFR according to the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault/body surface area (CG/BSA), creatinine clearance (CrCl) and mGFR (125I-iothalamate) changes from 3 months until 5 years post-donation.

Results

Donors had a pre-donation mGFR of 116 ± 23 mL/min, at 3 months post-donation mGFR was 73  ± 14 mL/min and at 5 years it was 79 ± 16 mL/min. Between 3 months and 5 years post-donation, 28% of donors had a declining mGFR (-0.82 ± 0.79 mL/min/year), 47% were stable and 25% had an increasing mGFR. Overall, eGFR equations showed good slope estimates (bias eGFRCKD-EPI 0.13 ± 2.16 mL/min/year, eGFRMDRD 0.19 ± 2.10 mL/min/year, eGFRCG/BSA -0.08 ± 2.06 mL/min/year, CrCl -0.12 ± 4.75 mL/min/year), but in donors with a decreasing mGFR the slope was underestimated (bias eGFRCKD-EPI 1.41 ± 2.03 mL/min/year, eGFRMDRD 1.51 ± 1.96 mL/min/year, eGFRCG/BSA 1.20 ± 1.87 mL/min/year). The CrCl had a high imprecision [bias interquartile range -1.51-3.41 mL/min/year].

Conclusions

All eGFR equations underestimated GFR slopes in donors with a declining GFR between 3 months and 5 years post-donation. This study underlines the value of mGFR in the follow-up of donors with risk of progressive GFR loss.