THE USE OF RENAL FUNCTIONAL RESERVE (RFR) AS A TOOL TO ASSESS KIDNEY FUNCTION IN POTENTIAL LIVING KIDNEY DONORS WITH BORDERLINE EGFR

E-Poster

https://storage.unitedwebnetwork.com/files/1099/f23203baf831296d325ae02633adebc7.pdf

Abstract Title

First Name *

Maria

Last Name *

Giordani

Co-author 1

Carlos Musso carlos.musso@hospitalitaliano.org.ar Hospital Italiano de Buenos Aires Nephrology Ciudad Autonoma de Buenos Aires

Co-author 2

Susana Villamil susana.villamil@hospitalitaliano.org.a Hospital Italiano de Buenos Aires Nephrology Ciudad Autonoma de Buenos Aires

Co-author 3

Tomás Fescina tomas.fescina@hospitalitaliano.org.ar Hospital Italiano de Buenos Aires Nephrology Ciudad Autonoma de Buenos Aires

Co-author 4

Carlos Schreck carlos.schreck@gmail.com Hospital Italiano de Buenos Aires Nephrology Ciudad Autonoma de Buenos Aires

Co-author 5

Co-author 6

Co-author 7

Co-author 8

Co-author 9

Co-author 10

Co-author 11

Co-author 12

Co-author 13

Co-author 14

Co-author 15

Introduction

Kidney function in potential living kidney donors is assessed through different methods. Guidelines suggest the age-adjusted GFR threshold by which these donors could be accepted. When lacking a reference method (51Cr-EDTA, 125I-iothalamate or iohexol), the use of RFR can help make a decision in potential donors with borderline eGFR. We present 2 cases in which the use of RFR was useful to assess kidney function in potential living kidney donors with borderline eGFR.

Methods

GFR was assessed by 24-hour Creatinine clearance (CrCl), and eGFR was calculated using the 2021 CKD-EPI Cr or 2021 CKD-EPI Cr-Cys when cystatin-C was available. RFR was calculated as the percentage increase in CrCl after a dairy protein meal. Briefly, patients received cimetidine 2 days before the test to inhibit Cr tubular secretion and they were put on a 2-day low protein diet to standardize the test in patients with varying protein intakes.

Results

We present 2 potential donors with borderline eGFR according to the KDIGO and UK living donor guidelines. Both potential donors were elderly women (75 and 61 years old). Pre-donation results are resumed in Tables 1-2.

Table 1

Donor	Age	SCr (mg/dl)	S Cystatin-C (mg/L)	eGFRCr (ml/min/1.73m2)	eGFRCr-Cys (ml/min/1.73m2)	24h-CrCl (ml/min/1.73m2)
1	75	0.82	1.19	75	65	60.3
2	61	0.84	0.87	79	87	78.9

Table 2

Donor	Albuminuria (mg/d)	Hypertension	Baseline CrCl (RFR) (ml/min/1.73m2)	Peak CrCl (RFR) (ml/min/1.73m2)	RFR (% increase from baseline)
1	< 5.6	Yes (mild)	55.6	151.1	171.8
2	< 5	No	65.6	159.1	142.5

Both patients were accepted for donation due to the response in GFR to the protein meal. After donation, SCr (mg/dl) increased from 0.82 to 1.12 and 0.84 to 1.11, respectively. eGFR as CKD-Epi-Cr, ml/min/1.73 m2 was assessed 11 and 13 days after uninephrectomy. It decreased from 75 to 52 (31%) and 65 to 56 (14%), respectively.

Conclusions

An accurate measurement of GFR is important in potential living kidney donors to determine the risk of developing chronic kidney disease (CKD). The donor GFR can be reduced due to aging and not to CKD. The RFR can help distinguish between these two conditions and avoid the erroneous exclusion of donors with a low risk of developing CKD.

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