PMC3737622_01
MRU appearance of circumcaval ureter. (A) The "sea horse" appearance of a type 1 circumcaval ureter seen on thick slab T2 turbo spin echo coronal MRU image. (B) axial T2-weighted HASTE MRU depicting the ureter coursing around the IVC
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F1
MRU was performed. MRU showed grade 4 hydronephrosis with the medialized segment of the ureter coursing around the IVC, and axial sections clearly depicted the anatomy [Figure 1].
PMC3737622_02
PMC3737622_03
PMC3737622_04
PMC3737622_05
Circumcaval ureter with calculus in the proximal obstructed ureter. (A) IVU showing grade-4 hydronephrosis and an opacity adjacent to L3 vertebral pedicle (arrow). (B) Axial MRU section clearly showing the ureteric segment posterior to the IVC with a signal void of a calculus in that segment (arrow). (C) T2-turbo spin echo coronal thick slab MRU showing the calculus as a signal void (upper arrow) and the circumcaval course of the ureter (lower arrow)
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F2
MRU unequivocally depicted the circumcaval course of the ureter and two calculi proximal to the obstruction [Figure 2].
PMC3737622_06
Grade-2 hydronephrosis with circumcaval ureter seen on thick slab T2-turbo spin echo coronal MRU image. The hooking of the proximal ureteric segment can be appreciated (arrow)
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F3
MRU showed grade 2 obstruction due to hooking of the proximal ureter around the IVC [Figure 3].
PMC3737622_07
Crossing vessel causing ureteric compression. (A) IVU showing grade-2 to -3 hydronephrosis with a grossly dilated pelvi-urteric segment and no cause for obstruction. (B) retrograde pyelography showing the catheter tip (upper arrow) to be superior and medial to the obstructed ureter (lower arrow) suggesting that this segment might be hooked around the IVC. (C) coronal MRU section showing a vessel (arrow) crossing at the site of ureteric narrowing, yielding the diagnosis
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F4
MRU was performed, and though the procedure had to be terminated prematurely owing to the patient's claustrophobia, the obtained sections excluded a circumcaval course of the ureter and were suggestive instead of a crossing vessel [Figure 4].