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Antenatally diagnosed, intermittently worsened hydronephrosis caused by a ureteral polyp

Congenital hydronephrosis is commonly caused by a ureteropelvic junction obstruction (UPJO), which is caused by a developmental anomaly of the ureter in fetal life. This results in stenosis, kinking or vessel compression in the upper part of the ureter. A ureteral polyp is a very rare cause of UPJO and was first reported in 1958. In 2007 two case reports were published, bringing the total now to approximately 40 reported pediatric cases of ureteral polyps in the UPJ. Here we report a new case of ureteral polyp that caused hydronephrosis. This case was antenatally diagnosed as a left hydronephrosis and several episodes of intermittent worsening of hydronephrosis were experienced since infancy.