Case Report: Ureteral obstruction reveals rare underlying fibro-inflammatory, infiltrative, and proliferative disorders: report of four cases.

Introduction: Ureteral wall thickening or a periureteral "sleeve" on imaging often raise concern for malignancy, but rare non-carcinomatous disorder can mimic this presentation. We report radiology and pathology findings of four prototypical cases of ureteral obstruction due to rare diseases. Case presentation: We describe four cases presenting with nonspecific urological symptoms such as flank pain, hydronephrosis, and variable degrees of renal dysfunction, in whom computed tomography revealed segmental or circumferential periureteral thickening suggestive of an infiltrative process. Given the absence of specific clinical or laboratory findings, a biopsy was required to confirm the diagnosis in all cases. Four different and rare diseases were diagnosed, namely light-chain amyloidosis, idiopathic retroperitoneal fibrosis, Erdheim-Chester disease, and Gardner's syndrome. Key imaging and pathology features are presented. Discussion and conclusions: Obstructive nephropathy may reveal rare fibro-inflammatory, infiltrative and proliferative diseases that require a thorough diagnostic work-up. Raising awareness of these rare conditions is crucial to guarantee timely diagnosis and effective treatment.