SUMMARY
We present a ten-year-old boy with episodic left flank pain, vomiting and microscopic hematuria. Imaging showed hydronephrosis characteristic for ureteropelvic junction (UPJ) obstruction. Pyeloplasty revealed a ureteral polyp, histopathologic examination confirmed the diagnosis of a fibroepithelial polyp. Fibroepithelial polyps of the ureter are a rare cause of UPJ obstruction in children. The most common presentation is episodic flank pain and/or hematuria. Imaging can be guiding, but pre-operative diagnosis is difficult. After surgical resection recurrence is rare.