Megaureters due to bilateral duplex kidneys (prenatal and neonatal imaging)
This is a case of megaureters in a female fetus. The most important differential diagnosis to rule out in such clinical context in prenatal diagnosis is a persistent cloaca, for it bears a poor prognosis (severe perineal malformation with bladder exstrophy and a common urogenitorectal sinus with or without sacral and spinal cord defects). The detailed US is critical, and MRI has a significant plus-value to assess the meconial physiological colon filling and spine cord examination. In this case, cloaca has been ruled out.
The bladder remained normally filled, non-distended: this is not a case of lower urinary tract obstruction (LUTO) (i.e below bladder obstacle), but rather a case of bilateral lower ureter obstacle or ectopic insertion. On strict axial scan, the ureteral end-pouches were seen lower than the bladder. The uterus was not seen on prenatal imaging (no obvious hydrometrocolpos). The amniotic fluid remained oddly normal throughout pregnancy, indicating normal diuresis.
The bilateral kidney duplex system was not properly identified on prenatal imaging: it has been diagnosed on the neonatal US. However, normal amniotic fluid and normal blood creatinine levels at day 3 are easily explained by the duplex collecting system and are additional clues leading to right diagnosis. Moreover, with a retrospective examination, a lower normal pyelix could be seen on both US and MRI on the right side. Still very hard to see on the left.
Dr F Cuillier and Dr M Balu also significantly contributed to this case.