During endoscopic procedures for suspected urothelial tumors of the upper urinary tract, radiographic imaging using an iodinated contrast medium is often required. However, following ureteropyelography, we detected changes in cytology characteristics not correlating with real cytology findings in naive urine. The aim of our study was to assess cytology changes between naive and postcontrast urine according to The Paris System of cytology classification. Methods: We prospectively assessed urine samples from 89 patients (23 patients with histologically proven urothelial cancer and 66 healthy volunteers). The absence of malignancy was demonstrated by CT urography and/or ureteroscopy. The study was single blind (expert cytopathologist) and naïve Paris system for urine cytology assessment was used. Furthermore, additional cytological parameters were analyzed (e.g., specimen cellularity, degree of cytolysis, cytoplasm and nucleus color, chromatin and nucleo-cytoplasmic ratio). Results: Our study showed statistically significant differences when comparing naïve and postcontrast urine in healthy volunteers (only 51 % concordance, p = 0.001) versus malignant urine specimens (82 % concordance). The most important differences were in the shift from The Paris System category 2 (negative) to 1 (non-diagnostic) and from category 2 (negative) to 3 (atypia). Other significant changes were found in the assessment of specimen cellularity (p = 0.0003), degree of cytolysis (p = 0.001), cytoplasm color (p = 0.003), hyperchromasia (p = 0.001), course chromatin (p = 0.002), nucleo-cytoplasmatic ratio (p = 0.001) and nuclear borders' irregularity (p = 0.01). Conclusion: Our unique study found crucial changes in the cytological assessment of naive and postcontrast urine and we confirm that postcontrast urine is more often assessed as abnormal, suspect or non-diagnostic. Therefore, before urine collection for cytology, the clinician should avoid administration of iodinated contrast into the urinary tract.

Department of Clinical and Molecular Pathology Institute of Molecular and Translational Medicine Medical Faculty Palacký University 77900 Olomouc Czech Republic

Department of Clinical and Molecular Pathology University Hospital Olomouc 77900 Olomouc Czech Republic

Department of Medical Biophysics Medical Faculty Palacký University 77900 Olomouc Czech Republic

Department of Urology University Hospital Olomouc 77900 Olomouc Czech Republic

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