Kidney Week

Abstract: FR-PO096

Lower Fractional Excretion of Urinary Sodium among Patients with Muddy Brown Granular Casts Does Not Portend Lesser AKI Severity

Session Information

• AKI: Diagnosis and Outcomes
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 102 AKI: Clinical, Outcomes, and Trials

Authors

• Punukollu, Pooja Ashley, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Pooja Ashley Punukollu

• Varghese, Vipin, University of Michigan Division of Nephrology, Ann Arbor, Michigan, United States

Vipin Varghese, MD

• Baguley, Joshua, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Joshua Baguley

• Kiely, Conor, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Conor Kiely, MS

• Gerschultz, Jaclyn Rose, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Jaclyn Rose Gerschultz

• Lewis, Stephanie K., UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Stephanie K. Lewis

• Muhtaseb, Rami N., UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Rami N. Muhtaseb

• Chalmers, Dustin R., Louisiana State University, Baton Rouge, Louisiana, United States

Dustin R. Chalmers, MD, MS

• Velez, Juan Carlos Q., UQ-Ochsner Clinical School, New Orleans, Louisiana, United States

Juan Carlos Q. Velez, MD, FASN

Group or Team Name

• Ochsner Group.

Background

We previously reported poor concordance between fractional excretion of urinary sodium (FENa) and presence of muddy brown granular casts (MBGCs) by microscopic examination of the urinary sediment (uSEDI) in that patients with acute tubular injury (ATI) can present with abundant MBGC and yet have a low FENa (<1%) [suggesting prerenal acute kidney injury (AKI)]. It has been hypothesized that cases with MBGC and low FENa may reflect early ATI whereas those with high FENa (>1%) reflect advanced ATI. To probe for this, we examined AKI outcomes stratified by uSEDI and FENa.

Methods

We conducted a prospective observational study of patients with AKI seen in inpatient nephrology consultation over 6-yrs in whom uSEDI was performed and a FENa was simultaneously obtained. Outcomes examined included: need for dialysis (AKI-RRT) and acute kidney disease (AKD) (increase in serum creatinine (sCr) >1.5 times baseline sCr) at discharge.

Results

FENa and uSEDI were completed in 489 patients, 44% women, median age 59. Median sCr was 3.4 mg/dL. Main etiologies of AKI were ischemic ATI (41%) and toxic ATI (12%). Greater than 10% low power fields with MBGCs (MBGC+) were found in 180 patients (37%). MBGC+ with FENa <1% were found in 78 (43%) whereas MBGC+ with FENa ≥1% were found in 102 (57%). Thus, uSEDI/FENa concordance for ATI was 59% (kappa 0.17, slight agreement). When concordance assessment was restricted to oliguric patients (urine volume <500 mL/day), it modestly improved to 68% (kappa 0.29, fair). AKI-RRT occurred in 41% of the MBGC+/FENa≥1% group and in 46% of the MBGC+/FENa<1% group (p=0.50). AKD occurred in 38% of the MBGC+/ FENa≥1% group and in 29% of the MBGC+/FENa<1% group (p=0.20). Peak sCr was slightly greater in the MBGC+/ FENa≥1% group [5.1 (IQR 4.0-7.8) vs 4.6 (IQR 3.4-6.5) mg/dL], p=0.04 (statistically significant, not clinically significant).

Conclusion

Our findings do not support the hypothesis that in cases with MBGC+, a low FENa may reflect earlier stage of ATI or a less severe insult. In addition, our findings confirm poor concordance between uSEDI and FENa in ATI but do support prior contention that FENa performs slightly better during oliguria.