Intrarenal cystic mass with pelviureteral junction obstruction

An abdominal mass in the first year after birth most commonly originates from the kidney. Renal masses in this age group are often cystic and may be associated with other abnormalities. We describe an unusual benign unilateral cystic lesion and coexisting pelviureteral junction obstruction in a newborn male with an otherwise morphologically and functionally normal urinary tract. A near normal kidney resulted from subsequent resection of the cyst wall combined with pyeloplasty.