CASE REPORTA 36-year-old primigravida with an unremarkable medical history was referred to our center at 25 + 3 weeks' gestation. At 21 weeks, she had been diagnosed with a fetal intravesical ureterocele associated with right renal duplication and progressive bilateral hydronephrosis, which was visualized in consecutive scans (Figure 1). Fetal karyotype was normal (46,XX). Because of progressive megacystis, due to urethral obstruction with bilateral hydronephrosis, associated with increasing oligohydramnios, referral for evaluation for fetal therapy was recommended. Ultrasound evaluation at admission confirmed severe bilateral hydronephrosis with pelvic and calyceal dilatation. Surprisingly, the amniotic fluid index (AFI) was within normal range and the cystic mass could not be visualized in the bladder. In fact, the bladder was normal in size with hypertrophic walls. The cystic mass was located between the labia of the vulva and was seen connecting with the bladder in an hourglass shape (Figure 2 and Videoclip S1). A full anatomical survey and detailed echocardiography were performed, excluding associated anomalies. Fetal growth was within the normal range for gestational age and location of the placenta was posterior.A presumptive diagnosis of prolapsed ureterocele causing intermittently severe obstruction of the urethra was suggested. Although AFI was normal at this time, oligohydramnios had been observed previously (Figure 1). Given the early gestational age and the unpredictable