Urinary sediment microscopy in COVID-19-associated AKI

Background: Acute kidney injury (AKI) is a complication of COVID-19 that is not fully understood Microscopic examination of the urinary sediment (MicrExUrSed) is a valuable diagnostic tool in AKI Thus far, there has been scarcity of data about MicrExUrSed in COVID-19-associated AKI (CoV-AKI) We hypothesized that MicrExUrSed provides diagnostic clues in CoV-AKI Methods: We conducted a prospective observational study in patients seen for inpatient nephrology consultation with KDIGO AKI stage ≥ 1 and COVID-19 over a 1-month period Urine specimens were collected with personal protective equipment to perform MicrExUrSed Slides were assessed for presence of white blood cells (WBC) [≥ 2+ dipstick, ≥ 6 per low power field (LPF)], red blood cells (RBC) (≥ 2+ dipstick, ≥ 8 per LPF), acanthocytes, granular casts (GC), renal tubular epithelial cell casts (RTECC) and waxy casts (WxC) Slides were assigned to a category of acute tubular injury (ATI) based on either a Perazella cast score ≥ 2 or a Chawla cast score ≥ 3 Results: Among 161 cases of AKI, MicrExUrSed was performed in 20 (12 4%) Anuria and contact precautions were barriers to obtain specimens GC were found in 17 (85%) of which 16 (80%) had 'muddy' brown GC (MBGC) A median 5 MBGC per LPF (1-20) were found in a median 40% (10-95%) of LPFs WxC were found in 10 (50%) cases with a median 2 (1-5) per LPF, all of whom had MBGC also present RTECC were found in 3 (15%) cases with a median 1 (1-4) per LPF Altogether, ATI score was assigned to 17 (85%) patients, of which 12 (60%) had AKI either after a hemodynamic/ischemic insult (9) or after a toxic insult (3) (rhabdomyolysis, vancomycin, contrast) and 3 (15%) had biopsy-proven ATI along with collapsing glomerulopathy;for a total of 15 (75%) patients with either clinical or histological evidence on ATI matching the MicrExUrSed findings Ten (50%) and 5 (25%) had WBCs and RBCs, respectively Acanthocytes were found in 1 (5%) patient with presumptive proliferative endocapillary glomerulonephritis Conclusions: MicrExUrSed in most patients with CoV-AKI showed overt evidence of ATI with an abundance of MBGC and WxC, including in cases of coexisting glomerulopathy Pyuria was observed in half The diagnostic utility of MicrExUrSed in CoV-AKI was comparable to that demonstrated in other forms of AKI