Flower vase ureter | Radiology Signs

Answer:

The flower vase or drooping lily appearance of the ureters describes the course of the ureters in a horseshoe kidney: they arise from anteriorly placed renal pelves, course laterally over the fused lower poles and then curve medially and inferiorly, so that the pair resembles the stems of flowers in a vase. The associated findings are the classic ones of a horseshoe kidney: low-lying, medially rotated kidneys with an isthmus crossing the midline, usually of functioning parenchyma, at the level of the third to fourth lumbar vertebra, the ascent of the kidneys during development having been arrested by the inferior mesenteric artery. The clinical relevance is in the complications, which is why the anomaly is worth reporting carefully: pelviureteric junction obstruction from the high insertion and the anterior pelvis, stasis leading to calculi and infection, an increased incidence of vesicoureteric reflux, and a raised risk of certain tumours including Wilms tumour in children and transitional cell carcinoma and, notably, renal carcinoid. The variable and often multiple arterial supply, which may arise from the aorta, the iliac arteries or the inferior mesenteric artery, must be mapped with CT angiography before surgery or before aortic aneurysm repair, since the isthmus lies directly over the aorta. The anomaly is also associated with Turner syndrome and trisomy 18.

Why is it called so?

The laterally displaced, gently curving ureters resemble the stems of flowers splaying out of a vase.

Pathophysiology

During the sixth week of development the two metanephric blastemas lie close together in the pelvis and their lower poles may fuse across the midline. The resulting isthmus prevents normal ascent and normal rotation, because the fused kidney is caught beneath the inferior mesenteric artery as it rises. The renal pelves therefore remain directed anteriorly rather than medially, and the ureters, which arise anteriorly and must pass over the bulk of the isthmus and the lower poles, take a laterally displaced and elongated course before descending to the bladder. That course impairs drainage and predisposes to obstruction, stasis, calculus formation and infection, and the anterior position of the kidneys makes them more vulnerable to blunt abdominal trauma.

Alternative names: Flower vase ureters; horseshoe kidney ureteric course

Other associated named signs: Drooping lily sign of a duplex system and the isthmus sign of the fused lower poles

References

1. Houat AP, Guimarães CTS, Takahashi MS, Rodi GP, Gasparetto TPD, Blasbalg R, et al. Congenital Anomalies of the Upper Urinary Tract: A Comprehensive Review. Radiographics. 2021;41(2):462-486. PMID: 33513074.