Synchronous and bilateral inverted papilloma of the kidney pelvis. Conservative treatment

: Contribution of a new case of inverted papilloma (IP) of the upper urinary tract (UUT) with the idiosyncrasy of being bilateral and synchronic, a fact not found in the reviewed literature, treated with radical surgery on the left side and conservatively on the right one. Discussion on this pathology is addressed, emphasising its benign biological behaviour, which does not eliminate some cases of malignization. Treatment has to be conservative, and so we stress the relevance of defining a suspicion state to make pre- and peri- operative diagnosis in which endourological methods, that allow both direct visualization and the taking of a biopsy, play a preeminent role. Subsequent strict monitoring is essential due to the likelihood of relapse and malignant changes.