Is it always necessary to treat a ureteropelvic junction syndrome?

The term ureteropelvic junction (UPJ) obstruction covers different morbid entities, and the old aphorism, "A UPJ is not a UPJ" remains true. Hydronephrosis is readily seen on antenatal ultrasonography but does not necessarily imply obstruction. Although most cases will resolve spontaneously, the probability of a significant pathology is related to the degree of pyelectasis, as seen on the third trimester study. Criteria of obstruction are difficult to define with precision, but two that are well-accepted are size of the renal pelvis (> 15 mm) and relative renal function, as determined by adequate isotopic studies. A new therapeutic standard has been established, and minimally invasive surgery has finally dethroned its open rival. Possibly facilitated by robotic assistance, laparoscopic dismembered pyeloplasty is the present gold standard, albeit endopyelotomy remains the least invasive with similar results in carefully selected patients.