A subcutaneous ureteral bypass — a SUB — costs roughly $4,000 to $9,000 for a cat, including imaging, surgery and several days of intensive care.
It is a large sum, usually presented urgently, and the decision has to be made within a day or two. This page exists to make that decision an informed one.
"Big kidney, little kidney"
If someone has used that phrase, this is why.
A cat blocks one ureter — the tube from kidney to bladder — usually with a tiny calcium oxalate stone. It causes little obvious illness, and that kidney slowly dies over months while the other one compensates. The cat seems fine.
Then the second ureter blocks. Now there is no functioning drainage at all, the cat becomes acutely unwell, and the bloodwork looks catastrophic. On ultrasound one kidney is swollen and obstructed and the other is small and scarred — big kidney, little kidney.
The number that misleads
The kidney values on admission are not the prognosis.
Much of the apparent kidney failure is back pressure, not permanent damage. Relieve the obstruction and function frequently recovers substantially over the following days and weeks. Cats whose creatinine looked hopeless often go home with values that are manageable, or close to normal.
Owners are regularly asked to make a decision while looking at the worst number they will ever see. Knowing that the number is expected to improve changes that conversation entirely.
What a SUB is
Two tubes and a port.
One tube goes into the kidney, one into the bladder, and they are joined by a small titanium port that sits just under the skin on the body wall. Urine bypasses the blocked ureter completely.
The port is the clever part. It can be accessed with a needle in a conscious or lightly sedated cat, which is how the system is flushed at intervals to keep it clear of mineral debris — every few months for the rest of the cat's life.
Stent or SUB?
Ureteral stents are used more in dogs. In cats, stents obstructed and caused problems often enough that the SUB has largely replaced them at most centres.
If two hospitals quote you different devices, that is why, and it is a fair question to ask.
Outcomes
Genuinely good, which is what makes this worth its price.
Most cats survive the surgery, and the majority live for years afterwards with stable chronic kidney disease that is managed with diet and monitoring. For a cat that is completely obstructed, the alternative is death or euthanasia within days.
The risks and the ongoing commitment
Be clear-eyed about both.
- Blockage of the device with mineral debris — the commonest problem, and the reason for lifelong flushing
- Infection, which can require the device to be removed
- Leakage in the early period
- Ongoing cost: regular flushing, bloodwork and imaging for years
An owner who cannot commit to that follow-up should say so, because an unmonitored SUB fails.
Can it be managed medically?
For 24 to 48 hours it is reasonable to try — intravenous fluids, pain relief, and sometimes medication to relax the ureter — in the hope the stone passes.
But a stone lodged in a feline ureter, which is about the width of a pencil lead, usually does not move. And calcium oxalate stones cannot be dissolved by diet. Owners who know that struvite bladder stones dissolve often assume these will too and wait. They do not, and waiting is the one thing this situation does not allow.
Getting there
Availability is genuinely limited — a number of specialist referral centres and university hospitals, not general practices. If your cat is obstructed and your practice does not offer it, ask about referral immediately rather than at the next recheck. Time matters here.
Who isn't a candidate
- Concurrent condition: End-stage chronic kidney disease where the blocked kidney has no recoverable function and the other kidney is also failing — relieving the obstruction changes nothing.
- Other: Active untreated urinary tract infection, which markedly raises the risk of the device becoming infected and needing removal.
- Other: An owner unable to commit to lifelong follow-up — a SUB needs periodic flushing and monitoring for years, and an unmonitored device fails.
Common questions
How much does SUB surgery cost for a cat?
Roughly $4,000 to $9,000, covering ultrasound and radiographs, stabilisation, the device and surgery, and several days of intensive care afterwards. Ongoing costs follow — the device is flushed at intervals for the rest of the cat's life, with bloodwork and imaging alongside.
What is a subcutaneous ureteral bypass in cats?
A device that bypasses a blocked ureter. One tube enters the kidney, another enters the bladder, and they are joined by a small port sitting just under the skin. Urine flows around the obstruction. The port can be accessed with a needle to flush the system, which is done periodically for the rest of the cat's life.
What is the life expectancy of a cat with a SUB device?
Most cats survive the surgery and the majority live for years afterwards, generally with stable chronic kidney disease managed by diet and monitoring. Outcomes are better where the surgery is done promptly and where the owner keeps up with the flushing and monitoring schedule.
What is the difference between a ureteral stent and a SUB?
A stent is a tube placed inside the ureter to hold it open; a SUB bypasses the ureter entirely. Stents are used more in dogs. In cats they obstructed often enough that most centres now prefer the SUB, so two hospitals may quote different devices for the same problem.
Can a blocked ureter in a cat be treated without surgery?
It is reasonable to try 24 to 48 hours of fluids, pain relief and medication in the hope the stone passes. Most do not — a feline ureter is about the width of a pencil lead — and the calcium oxalate stones that cause the great majority of these obstructions cannot be dissolved by diet, so waiting rarely helps and can cost the kidney.
Sources
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