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Kidney Week

Abstract: SA-PO545

Kidney Sodium MRI: Extending the Concept of Residual Kidney Function in Hemodialysis

Session Information

Category: Dialysis

  • 801 Dialysis: Hemodialysis and Frequent Dialysis

Authors

  • Lemoine, Sandrine, Hospices Civils de Lyon, Lyon, Auvergne-Rhône-Alpes , France
  • Akbari, Alireza, Western University, London, Ontario, Canada
  • Penny, Jarrin D., Western University, London, Ontario, Canada
  • McIntyre, Christopher W., Western University, London, Ontario, Canada
Background

It is widely recognized that persistence of even modest amount residual kidney function (RKF) is associated with improved outcomes, in hemodialysis (HD) patients. The concept of RKF, as currently utilized, is exclusively based upon urine volume and small solute clearance- requiring complete interdialytic urinary collection. This makes accurate and consistent assessment measurement challenging and difficult to implement in clinical practice. More importantly it focusses almost exclusively on glomerular function, rather than a more inclusive consideration of overall kidney function to incorporate assessment of renal tubular mass.
The aim of this study was to test the feasibility of obtaining useable 23Na-MRI kidney images, in the setting of dialysis dependance (as compared to normal subjects without CKD) and initially describe the associations between directly imaged medullary sodium content and other components of a more conventional approach to the definition of RKF.

Methods

We included 21 healthy volunteers and 17 HD participants, fasted for eight hours prior to their study visit. Urine samples were collected to measure urinary osmolarity, before MRI scan.

Results

Median (IQR) fasting medulla to cortex ratio was significantly higher 1.56 [1.5 – 1.61] in healthy volunteers compared to HD patients 1.22 [1.13 – 1.3], p<0.0001. Medulla to cortex ratio and median urinary osmolarity were correlated (r=0.87, p<0.0001) in the whole population. We found a significant association between HD vintage and medulla to cortex ratio whereas we did not find any association with urine volume. Sodium signal intensity distribution within healthy kidney describes two different peaks- relating to well defined cortex and medulla; whereas HD participants displays only a single peak indicative of the markedly lower sodium concentration.

Conclusion

The application of kidney sodium MRI to the study of RKF in patients receiving maintenance HD is practical and provides a previously unavailable ability to interrogate the function of remnant tubular mass.