Learning Radiology xray montage

Pyelovenous Backflow

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


  • None usually required


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