Urinary Diagnostic Cytology Beyond the Research of Neoplastic Cells: Usefulness of Erythrocyte Morphology Evaluation to Recognize Microhematuria Source

Background: Urine cytology is useful to diagnose urinary neoplasms, whereas its role in the study of microhematuria is debatable. Usually, standard urinalysis (dipstick test and sediment examination with bright field microscope) detects the presence of microhematuria, but only urinalysis with phase-contrast microscopy (PCM) (dipstick test and sediment examination with PCM) allows the observation of red blood cell (RBC) morphology and identify their source. Usually glomerular diseases show RBCs with morphological alterations in high percentages, whereas on urologic bleeding, RBCs are rather homogeneous without morphological alterations. Aims: We compare, for the first time, RBC morphology observed in urine cytology and in urinalysis with PCM, to verify whether urinary cytology allows the recognition of the source of bleeding. Methods and material: A total of 60 patients who had performed both urine cytology and urinalysis with PCM for microhematuria, detected with standard urinalysis, were investigated. Urine cytology showed RBCs and were negative for neoplastic cells or for inflammatory events. Urine samples were processed with the automated method ThinPrep®. RBCs with abnormal and variable shapes were defined as deformed. RBCs of the same spherical shape were defined as non-deformed. Results: Fifty-six urine cytology with RBCs deformed were confirmed in 55 urinalysis with PCM. One case showed RBCs non deformed in urine cytology and in urine sediment. Overall, agreement, between RBC morphology in urine cytology and urinalysis with PCM, was found in 56/60 cases (93%). Conclusions: Therefore, since sediment examination with PCM is available in only few laboratories, we propose that cytopathologist always reports, in urine cytology, any morphological abnormalities of RBCs in order to provide information of the hematuria origin and correctly refer the patient to a nephrologist rather than a urologist.