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Foreign body mimicking neoplasia of the renal pelvis on magnetic resonance imaging.

A 65-year-old male presented with an incidental magnetic resonance imaging (MRI) finding of a right renal pelvis (RP) tumor-like mass. He was subjected to nephrostomy tube (NT) placement due to hydronephrosis secondary to an impacted ureteral stone. NT was removed after successful Ho:YAG laser lithotripsy. Abdominal MRI performed 19 months later for another indication showed RP wall thickening/enhancement and an intrapelvic low-intensity linear structure presenting as a magnetic susceptibility artifact. He underwent diagnostic ureterorenoscopy/retrograde intrarenal surgery. A calcified NT locking suture remnant was found within the pelvis surrounded by reactive edema without evidence of tumor. Foreign body (FB) was removed after disintegration of surrounding calcifications using Ho:YAG laser. This is the first case of a calcified NT locking suture remnant mimicking RP tumor on MRI. The case underlies the importance of safe NT removal. Specific MRI findings may prove valuable for preoperative diagnosis of intrarenal FBs in cases with history of endourological interventions evaluated for upper urinary tract masses. Multidisciplinary-uroradiological approach of such cases is essential.