Megaureters due to bilateral duplex kidneys (prenatal and neonatal imaging)

Bilateral megaloureterasmegaureters as seen on US.The most important findings of MRI are :-well limited bladder within pelvic area (no extrophy)-normal meconial filling of the colon with physiological rectal pouch-normal spinal cord and no sign of sacral defect-no obvious hydrometrocolposThese findings are important to rule out cloacal malformationassociated malformations in the spectrum of a persistent cloaca in a female fetus.A sharp eye may witness a separate pyelix at the lower pole of the right kindney on the coronal T2w image…

Stable situation at 31WG:Bilateral megaloureterasmegaloureters followed all the way from the renal pelvis to below the bladder. Bladder is identified thanks to the ombilicalumbilical arteries at its borders drawing a Y shape.Bladder does not appear distended, no internal image of ureterocele.This is a female fetus.Enlarged kidneys, with normal parenchymal thickness and differentiationparenchyma : no thinning, no hyperechoic aspect.A sharp eye may witness a separate pyelix at the lower pole of the right kindney on the axial US scan…Oddly, calyces are non dilated and amniotic fluid remains normal, while oligohydramnios/anhydramnios/anamnios might be expected in urinary obstacles.Careful US examination reveals normal small bowel. LargeThe transverse large bowel is clearly seen, normal, non dilated. Fetal anal sphincter is normal (not shown).

Duplex pelvis, with dilation of the superior pelvis and ureteraureters on both kidneys.Normal bladder.Normal uterus anatomy. 

• This is a case of Lower Urological Tract Obstruction (LUTO)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 extrophy and a common uro-genito-rectal tractsinus with or without sacral and spine cord defects). Detailed US is critical, and MRI has a significant plus-value to assess the meconial physiological colon filling and spine cord examination. In;In this case, cloaca has been ruled out.
• The bladder remained normally filled, non distended-distended: this is not a case of Lower Urinary Tract Obstruction (LUTO) (i.e below bladder obstacle), which indicated an ureterovesical junctionbut rather a case of bilateral lower ureter obstacle or ectopic insertion. On strict axial scan, the ureteral end-pouches endedwere seeb lower than the bladder. Uterus was not seen on prenatal imaging (no obvious hydrometrocolpos). The amniotic fluid remained oddly normal throughout pregnancy, indicating normal diuresis and likely preserved kindey function.

  US and MRI prenatal imaging could

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• We did not in this casehonestly properly identify the bilateral kidney duplex system, which was only seen in prenatal imaging: it has been diagnosed at neonatal US. Duplex collecting system hence easily relates toHowever, normal amniotic fluid and normal blood creatinine levels at dayDay 3 are easily explained by the Duplex collecting system and are additional clues leading to right diagnosis. Moreover, with retrospective examination, a lower normal pyelix could be seen on both US and MRI on the right side. Still very hard on the left :)…