Abstract: TH-PO105
Urinary Waxy Casts Are Associated with Greater Severity of Acute Tubular Injury
Session Information
- AKI: Biomarkers, Drugs, Onco-Nephrology
November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Rivera, Maria Soledad, The University of Queensland, New Orleans, Louisiana, United States
- Velez, Juan Carlos Q., The University of Queensland, New Orleans, Louisiana, United States
Background
Waxy casts (WxCs) constitute a recognized finding during microscopic examination of the urinary sediment (MicrExUrSed) and they are classically linked to chronic kidney disease (CKD). It is less clear whether WxCs are a relevant finding in acute kidney injury (AKI). We hypothesized that identification of WxCs in AKI due to acute tubular injury (ATI) provides prognostic information.
Methods
We conducted a prospective observational study in patients seen in the inpatient nephrology consultation team with AKI stage ≥ 1 (AKIN) over a 1.5-yr period. On the day of the consult, MicrExUrSed was performed to determine the percentage of low power fields (lpf) with WxCs and to assess a validated score for ATI based on granular casts and tubular epithelial cells per lpf [Perazella score (PS): score ≥ 2 consistent with ATI]. The primary outcome measure was need for dialysis at 30 days (RRT).
Results
Urine specimens from 167 patients [median age 58 (25 – 88), 43% women] were assessed. The etiology of AKI (pure de novo AKI 56%, AKI on CKD 44%) was ischemic ATI (41%), toxic ATI (14%), ischemic/toxic ATI (17%) and others (28%). WxCs were found in 47 patients (28%), 33 (70%) of which had pure de novo AKI. Median serum creatinine for those with WxCs was 3.7 (2.8 – 4.9) mg/dL compared to 3.1 (2.4 – 4.6) mg/dL for those without WxCs (p = 0.087). Having >10% lpf w/ ≥1 WxCs was associated with greater risk for RRT [relative risk (RR): 2.3, CI 1.4 – 3.5, p = 0.0003). As reported by others, PS ≥ 2 was associated with increased risk for RRT (RR: 2.6, CI 1.1 - 6.6, p = 0.04). When presence of WxCs was added to a PS ≥ 2, the RR for need for RRT became stronger (RR: 6.0, CI 2.9 - 12.5, p< 0.0001). In addition, the greater the abundance of WxCs, the greater the need for RRT: need for RRT was 26% (31/120), 43% (20/47), 59% (13/22), and 60% (6/10) for those with none, >0%, >10% and ≥50% lpf w/ ≥1 WxCs, respectively (p = 0.0003 for chi-square for trend).
Conclusion
WxCs can be found in a significant proportion of patients with AKI, even among those without preexisting CKD. Among patients with ATI, the presence and abundance of WxCs are associated with a greater risk for need for RRT, suggesting that WxCs carry similar and potentially additive prognostic value to that of granular casts.