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Abstract: PO1109

Functional Sodium Magnetic Resonance Imaging of Human Kidney

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Lemoine, Sandrine, Western of ontario, London, Ontario, Canada
  • Akbari, Alireza, Western of ontario, London, Ontario, Canada
  • Salerno, Fabio R., Western of ontario, London, Ontario, Canada
  • Scholl, Timothy J., Western of ontario, London, Ontario, Canada
  • Filler, Guido, Western of ontario, London, Ontario, Canada
  • House, Andrew A., Western of ontario, London, Ontario, Canada
  • McIntyre, Christopher W., Western of ontario, London, Ontario, Canada

Group or Team Name

  • Kidney Clinical reserach unit, Western of Ontario, Pr McIntyre
Background

Maintenance of a cortico-medullary concentration gradient (CMG) is required for urine concentration. We explored the ability of 23NaMRI in measuring 1) the dynamics of CMG for the first time compared to urinary osmolarity after a water load and 2) the CMG in kidney disease.

Methods

We conducted an exploratory pilot study for 10 healthy controls following water load then 5 cardiorenal patients with kidney disease. 1) Fasting healthy controls provided urine samples to measure osmolarity and baseline 23NaMRI scans were performed. They were instructed to ingest water (15 mL/kg) within 15 minutes. Four subsequent sodium images and urine samples were acquired at 15 min intervals starting one hour after water ingestion. 2) Cardiorenal patients underwent an MRI scan, provided a blood and urine sample, but no water loading.

Results

Mean age of the 10 healthy controls was 41.8 ± 15.3 years. In the morning fasting, medulla/cortex ratio was 1.55 ± 0.11 with concurrent urinary osmolarity measured at 814 ± 121 mOsm/L. Mean ± SD fasting urinary osmolarity dropped significantly to 73 ± 14 mOsm/L, p=0.001. Mean medulla/cortex ratio dropped significantly to 1.31 ± 0.09 mOsm/L for maximal dilution, p=0.002. Figure 1 displays changes of 23NaMRI pictures before (A) then 1h (B), 1H15 (C), 1h30 (D) and 1h45 (E) after a water load. Urinary osmolarity and medulla/cortex ratio are significantly correlated, r=0.54, p=0.0001.
Mean age of the 5 cardiorenal patients was 76.6 ± 12.2 years, eGFR was 54 ± 37 mL/min/1.73m2. Urinary osmolarity was 498 ± 145 mOsm/L and medulla/cortex ratio was 1.35 ± 0.11. We measured corticomedullary gradient in cardiorenal patient with different level of eGFR to show the ability and feasibility to measure this gradient in pathological settings.

Conclusion

We explored CMG dynamically every 15 min in healthy controls and demonstrated significant changes after a water load. We were also able to acquire 23NaMRI pictures in cardiorenal patients with kidney disease with plans for future analyses.