Persistent hydronephrosis after pyeloplasty is a common finding. Depending on the definition used, as few as 13.8% of children who undergo pyeloplasty achieve complete resolution of hydronephrosis on the affected side. A clinical challenge is determining if persistent renal swelling is indicative of a recurrent obstruction. Worsening hydronephrosis, decreasing renal function, increasing flank pain, developing urinary tract infections, or growing new kidney stones can all be clinical indicators of obstruction. Dynamic investigations, including renal scintigraphy, retrograde pyelography, and ureteroscopy, can provide additional information. Treatment of recurrent ureteropelvic junction obstruction can involve endoscopic management with incision or dilation, or redo pyeloplasty. Adjunctive techniques utilizing grafts or flaps, or ureterocalycostomy, may be necessary based on individual anatomy.