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)
Options
- 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)