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Ureteral Obstruction

The ureter is the tube between the kidney and bladder

Ureter size

  • Canine ureter 1-3 mm internal diameter
  • Feline ureter approximately 0.5 mm internal diameter

Causes of Obstruction

  • Ureteroliths (kidney stones lodged in the ureter)
  • Strictures (scar tissue)
  • Neoplasia (tumor)
  • Extraluminal compression (obstruction caused by something outside of the ureter compressing it)

Consequences of Obstruction

  • Blood flow to the kidney is diminished immediately
  • Permanent damage in less than a week
  • Medical therapy should be attempted for no more than 24 hours
  • if no resolution, need to be more aggressive to save kidney
  • Bilateral obstruction can be fatal within hours to days
    • Inability to eliminate potassium leads to fatal cardiac arrhythmia (irregular heart rhythm)


  • Ureterotomy – cutting into the ureter to remove obstruction
  • Stricture or leakage in 20-40% of cases even in the most experienced hands
  • Ureteronephectomy – removing the kidney and ureter
  • Low short-term complication rate, but poor option long-term
  • 20-40% of pets may develop new stones within 4 months
  • Ureteral stents – recommended treatment for dogs
  • Subcutaneous Ureteral Bypass (SUB) - recommended treatment for cats (and dogs in some cases)