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Kidney Week

Abstract: PO0391

Clinical Outcomes in Patients with Calcifications on Kidney Biopsy

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Gaddy, Anna R., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Moorthi, Ranjani N., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Eadon, Michael T., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Schwantes-An, Tae-Hwi, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Phillips, Carrie L., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Moe, Sharon M., Indiana University School of Medicine, Indianapolis, Indiana, United States
Background

Calcification is often noted on kidney biopsies, but the consequences of this finding is not known.

Methods

We searched a biobank for specimens with at least two years of linked clinical data and identified those which had calcification on report. Biopsy specimens were further classified to be described as calcium oxalate (CO) , calcium phosphate/dystrophic (DC), or both. Linked clinical data was examined in 3 month intervals before and after index date of kidney biopsy. Cox proportional hazard analysis was performed using a split time model to evaluate relationships between presence of calcification, type of calcification, and clinical outcome endpoints. Linked clinical data was examined in 3 month intervals before and after index date of kidney biopsy. Cox proportional hazard analysis was performed using a split time model to evaluate relationships between presence of calcification, type of calcification, and clinical endpoints.

Results

Patients with any calcification (n=429) vs. without (n= 3936) were (p < 0.05) older, more likely to be white, have diabetes, lower eGFR and higher AKI/ATN on kidney biopsy specimen (31 vs. 13%),. Patients with COX (n = 126) vs. DC (n = 260) were older, less diabetes, lower eGFR, more likely to have malabsorption or gastric bypass, and used more vitamin D. By univariate analyses, patients with any calcification were more likely to have a decline in the slope of creatinine at 6 months, 1 year, and 2 years; these changes persisted even after adjustment for baseline eGFR, htn, proteinuria, negative biopsy findings, CAD (for 1 year beta 0.029, p < 0.001). When adjusted for age, diabetes, and baseline eGFR, patients with any calcification were less likely than those without calcification to advance to ESKD (HR 0.59; 95%CI 0.38-9.82; p < 0.05) but not to meet the outcome of death.

Conclusion

The presence of calcification on kidney biopsy specimen is associated with lower progression to ESKD and decrease in rate of decline of eGFR over time at 6 months, 1 year, and 2 years. This paradoxical finding may be due to increased AKI with recovery, rather than progressive chronic disease but requires further analyses.