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Kidney Week

Abstract: SA-PO194

Dimensions of Urinary Muddy Brown Granular Casts and Waxy Casts and Clinical Correlations

Session Information

  • AKI: Mechanisms - III
    November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Cohen, Lauren, Ochsner Health, New Orleans, Louisiana, United States
  • Antley, Mckinley H., College of Charleston, Charleston, South Carolina, United States
  • Chalmers, Dustin R., Louisiana State University, Baton Rouge, Louisiana, United States
  • Ramanand, Akanksh, Ochsner Health, New Orleans, Louisiana, United States
  • Velez, Juan Carlos Q., Ochsner Health, New Orleans, Louisiana, United States
Background

Muddy brown granular casts (MBGC) have distinctive microscopic characteristics and are pathognomonic of acute tubular injury (ATI). Waxy casts (WxC) are found in a wider range of tubular and glomerular diseases. There is significant variability in MBGC and WxC size. We aimed to determine whether cast dimensions may correlate with clinical parameters.

Methods

Urine specimens from patients seen in inpatient nephrology consultation were collected. Cases with specimens containing MBGCs or WxC were sampled. At least 12 casts per case were imaged using SeBaCam® and SeBaView at 40x to 400x magnification. Using ImageJ, each cast was measured lengthwise 3 times and widthwise 6 times for MBGC, and 10 times for WxC. Clinical data was extracted from medical records. Data was analyzed by Spearman correlation and t-test.

Results

Twenty-one patients with MBGC and 18 patients with WxC were included. The primary etiology of acute kidney injury (AKI) was ischemic ATI in 61%, toxic ATI in 11% and acute glomerulonephritis in 28%. Mean (range) length for MBGC was 102 (33-317) µm and 223 (28-1714) µm for WxC. Mean (range) width for MBGC was 35 (9-110) µm and 43 (5-253) µm for WxC. For MBGC, width significantly correlated with height (r=0.535, p=0.012), whereas length significantly correlated with age (r=-0.436, p=0.048), FENa (r=0.698, p=0.008), urine chloride (r=0.896, p=0.001) and urine phosphate (r=-0.717, p=0.03). Further, mean MBGC length was found to be significantly longer in patients that received dialysis (p=0.057). WxC length did not correlate with age, need for dialysis or any other parameter, whereas WxC width significantly correlated with serum creatinine (sCr) value at the time of urine microscopy (r=0.855, p<0.001).

Conclusion

MBGC and WxC dimensions significantly correlated with various antropometric, chemical and clinical parameters. Correlation of MBGC length with need for dialysis as well as WxC with sCr suggest that cast dimensions may be related to severity of AKI. With implementation of automated image scanners and computational model training, these observations suggest that urinary cast dimensions may provide valuable diagnostic and prognostic information. Further larger studies are needed to verify and expand these observations.