Recommendations for the standardization and clinical reporting of urinary sediment in the clinical laboratory

Abstract Microscopic examination of urinary sediment is a highly valuable diagnostic tool in the clinical laboratory, as it enables the direct identification of formed elements originating from different segments of the urinary tract and the kidney, providing relevant information for the detection and characterization of a wide range of renal and urological conditions. However, its clinical utility depends not only on the accurate morphological identification of these elements, but also on their appropriate interpretation and consistent reporting in the laboratory report. This document reviews the clinical relevance of the main urinary sediment findings, including epithelial cells, erythrocytes, leukocytes, casts, crystals, spermatozoa, and microorganisms, as well as virus-infected cells and cells suspicious for malignancy. Practical recommendations are proposed for their inclusion in laboratory reports, distinguishing findings of limited clinical significance or likely contaminant origin from those with high diagnostic value, such as renal tubular epithelial cells (RTECs), dysmorphic red blood cells (RBCs), cellular casts, specific crystalluria, decoy cells, and neoplastic cells. Furthermore, the importance of incorporating interpretative comments for clinically significant findings is emphasized, as well as the integration of sediment morphological information with other laboratory parameters, particularly urinary protein biomarkers. Standardization of urinary sediment reporting may reduce interobserver variability, improve communication between laboratory professionals and clinicians, and enhance the diagnostic utility of urinalysis in routine clinical practice.