Ureteropelvic junction obstruction in the fetus.

Ureteropelvic junction (UPJ) obstruction is being detected with increasing frequency before birth. To clarify the natural history of fetal UPJ obstruction, we reviewed our experience managing 28 fetuses; there were 16 bilateral cases for a total of 44 renal units. None required decompression before birth. We found that fetal bilateral UPJ obstruction is associated with significant morbidity and mortality; resolution of fetal hydronephrosis secondary to UPJ obstruction is rare; antenatal diagnosis of UPJ obstruction improves clinical management by allowing early detection and appropriate treatment of otherwise clinically undetectable disease; oligohydramnios in the mature fetus with bilateral UPJ obstruction is an indication for early delivery and immediate repair; and prenatally diagnosed UPJ obstructions should be repaired as early as possible after birth.