[Filling defects in the upper urinary tract: update on the etiologic diagnosis and review of the specific value of urinary cytology].

We present 3 cases with upper tract filling defect and exfoliative cytology positive for malignant cells in 2 of these cases (micturition and via ureteral catheter, respectively). The initial suspicion of urinary tract tumor was discarded by subsequent work up in 2 patients who were managed conservatively and followed closely. The third patient was submitted to nephroureterectomy. The histopathological examination disclosed chronic pyelonephritis and a deposit of amorphous mucoid material but no evidence of tumor. We review the etiologies of upper tract filling defects and present a useful diagnostic algorithm for the study of these conditions and the etiopathogenic and physiopathologic evaluation of the false positives in urinary cytology.