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Kidney Week

Abstract: FR-PO017

Diagnostic Utility of Serial Microscopic Examination of the Urinary Sediment in AKI

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical, Outcomes, and Trials

Authors

  • Alghamdi, Ayman M., Ochsner Clinic Foundation, New Orleans, Louisiana, United States
  • Rivera, Maria Soledad, The University of Queensland, New Orleans, Louisiana, United States
  • Velez, Juan Carlos Q., Ochsner Clinic Foundation, New Orleans, Louisiana, United States
Background


Urine microscopy is a clinical tool of diagnostic and prognostic value in acute kidney injury (AKI). However, the natural history and timing of cast formation remains underexplored. A single inspection of a urine specimen during the course of AKI is a mere snapshot that depends on the day of inspection. We hypothesized that longitudinal inspection of the urinary sediment provides additional diagnostic information otherwise not identified in a single inspection.

Methods

Microscopic examination of the urinary sediment (MicrExUrSed) +/- Sternheimer-Malbin stain was undertaken in all patients with AKI stage ≥ 2 who were seen on consultation in an inpatient nephrology service during a 6-month period. MicrExUrSed were done on the day of consult (day 1), 48 hours later (day 3) and 96 hours later (day 5). Urinary cast scores (based on Chawla et al and Perazella et al) were assigned to each specimen. Chawla scores (CS) 3-4 and Perazella scores (PS) 2-3 were categorized as consistent with acute tubular injury (ATI), whereas CS 1-2 and PS 0-1 were categorized as non-diagnostic for ATI (non-ATI). Worsening AKI was defined as a rise in serum creatinine (sCr) ≥ 0.3 mg/dL at either day 3 or 5.

Results


At least 2 serial specimens were collected in 60 patients (mean age 58, 32% women, mean sCr at day 1 3.8 mg/dL). Overall, CS and PS category changed over time in 16 (27%) patients, and the change was observed at day 3 in almost all cases (15 of 16). On day 1, a CS and PS consistent with non-ATI was assigned to 31 (52%) patients. Among those 31 patients, CS and PS changed from non-ATI category to ATI in 9 (24%) at day 3. Those 9 patients accounted for 32% of the total 38 with ATI score. Patients with worsening AKI were more likely to change their score from non-ATI to ATI compared to those with stable or improved AKI [relative risk 3.3 (CI: 1.0 – 10.9) for CS (p = 0.047); 8.3 (CI: 1.1 – 63.1) for PS (p = 0.041)].

Conclusion


Serial MicrExUrSed reveals diagnostic findings of ATI otherwise not identified in a single examination, particularly in specimens of patients with worsening AKI. A repeat MicrExUrSed within 48 hours may be warranted in cases of worsening AKI with unclear etiology.