General Considerations

• Refers to the retrograde flow of contrast material out of the intrarenal collecting system due to a small rupture of a calyceal fornix
• Almost always seen with increased pressure in the collecting system such as from
  • Retrograde pyelography
    • Majority of cases
  • Antegrade pyelography (urogram), due to obstruction of the collecting system almost always by a ureteral calculus
    • Less common
• Obstruction is usually in the ureter
• Rupture decompresses collecting system
• Rarely, from vesico-ureteral reflux

Clinical Findings

• Patients with acute ureteral obstruction may report relief of symptoms when rupture of collecting system occurs

Imaging Findings

• Types of backflow include
  • Pyelotubular
    • Backflow into terminal collecting ducts (papillary ducts)
    • Produces wedge-shaped striated area or blush extending from a calyx
    • Usually considered normal phenomenon
  • Pyelointerstitial
    • Interstitium of kidney
    • Like pyelotubular, produces wedge-shaped striated area or blush extending from a calyx, sometimes out to the edge of the renal cortex
  • Pyelosinus
    • Most common form
    • Contrast enters the renal sinus and tracks along infundibulae, renal pelvis and proximal ureter
    • Can obscure the collecting system
    • May be seen with excretory urography (antegrade)
  • Pyelolymphatic
    • Contrast enters peripelvic lymphatics
    • Multiple small channels in the hilum of kidney directed towards the para-aortic lymph node chain are visualized
    • May be seen with excretory urography (antegrade)
  • Pyelovenous
    • Rare
    • Contrast enters interlobar, arcuate renal veins
    • Static radiographs rarely catch this swift-moving event but rapid sequence images may

Treatment

• None usually required

Complications

• Urinoma
• Retroperitoneal fibrosis

 

 

Pyelovenous Backflow. Single image from a retrograde pyelogram shows the catheter
(dotted white arrow) in the left ureter. There is a slightly dilated collecting system (dotted yellow arrow).
There is extraluminal contrast in venous structures (yellow arrow), including the left renal vein (white arrow).
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For this same photo without the annotations, click here

Medcyclopedia

Pyelovenous Backflow Seen on CT Urography  Nemeth A and Patel S: AJR 2004; 182:532-533