Abstract: FR-PO1087
Kidney Medullary Oxygen Availability Is Higher in CKD: Truth or Fallacy?
Session Information
- CKD Mechanisms: Progression, Fibrosis, and Beyond
November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2303 CKD (Non-Dialysis): Mechanisms
Authors
- Prasad, Pottumarthi V., NorthShore University HealthSystem, Evanston, Illinois, United States
- Li, Luping, NorthShore University HealthSystem, Evanston, Illinois, United States
- Hack, Bradley K., NorthShore University HealthSystem, Evanston, Illinois, United States
- Leloudas, Nondas, NorthShore University HealthSystem, Evanston, Illinois, United States
- Sprague, Stuart M., NorthShore University HealthSystem, Evanston, Illinois, United States
Background
Chronic hypoxia hypothesis (CHH) suggests kidneys with progressive CKD are hypoxic. Currently Blood Oxygenation Level Dependent (BOLD) MRI is the only known technique to afford evaluation of kidney oxygen status in humans. Results to-date show higher R2* (i.e. lower O2 availability) in cortex but lower R2* in medulla (suggesting higher O2 availability) in CKD compared to controls. Whether the lower R2* in medulla in CKD an anomaly remains untested. Hypothesizing that reduced fractional blood volume (fBV) within tissue is the cause for this anomaly [PMID: 29571450], we measured fBV in CKD using ferumoxytol, an intravascular MRI contrast agent.
Methods
Data was available in 9 each in controls and individuals with CKD. After baseline R2* maps were acquired, ferumoxytol (5mg/kg) was administered and R2* measurement repeated. fBV, and oxygen saturation of hemoglobin (StO2) were calculated using equations described previously for brain MRI [31482602].
Results
Table 1 summarizes the R2*, fBV, StO2 and bloodPO2 for cortex and medulla. Consistent with prior reports, R2* in medulla is significantly lower in CKD implying higher O2 availability in CKD. However, when including the fact that fBV is lower in CKD, estimated StO2 and bloodPO2 are significantly lower in medulla.
Conclusion
Our data for the first time demonstrate that fBV is significantly lower in CKD in both cortex and medulla. When including this lower fBV, cortex and medulla are both moderately hypoxemic in CKD while in controls, cortex was normoxemic and medulla mildly hypoxemic. The blood pO2 estimates are consistent with the only report to-date in rat kidneys [16357065].
Funding
- NIDDK Support – Covis Pharma (providing drug)