When your beloved pet faces a complex medical issue, understanding the procedures involved is crucial. At Melbourne Animal Referral Services, our internal medicine veterinary team, led by specialists like Dr. Abigail Brough, is dedicated to providing clarity and expert care. Today, we’ll delve into the Subcutaneous Ureteral Bypass (SUB) procedure, a vital intervention for pets with ureteral obstructions. If you suspect your pet needs specialized care, don’t hesitate to contact our internal medicine veterinary team for a consultation.

What does the vet mean by SUB procedure? Our internal medicine team has the answer.

Subcutaneous Ureteral Bypass

Ureteral obstruction (from a stone, debris or ureteral stricture) is an uncommon but potentially catastrophic cause of acute renal failure. This condition can affect both species but is more commonly diagnosed in cats.

Cats with acute ureteral obstruction present with a condition we refer to as “Big kidney, little kidney syndrome”. This is because one kidney has usually become obstructed in the past and has become small and non-functional, but no symptoms were detected because the other kidney was able to compensate. However, when the second kidney becomes obstructed, patients go into acute renal failure.

This is diagnosed using a combination of ultrasound and a technique called EXCRETORY UROGRAPHY – whereby contrast is introduced directly into the renal pelvis and then a series of xrays are taken to observe the passage (or absence) of contrast down the ureter and into the urinary bladder.

If the obstruction is confirmed (as evident in the below radiograph) by a specialist veterinarian, then the best option available for treatment is to surgically implant a device called a SUBCUTANEOUS URETERAL BYPASS or “SUB”. This is a specialised device that shunts urine from the renal pelvis to the urinary bladder, thus bypassing the non-functional ureter (see radiograph below). The SUB has an access port located under the surface of the skin but outside the abdominal cavity that enables us to flush the SUB at three monthly intervals to prevent debris accumulation and infection.

Patients who have a SUB placed are often very sick in vet hospitals and need intensive care management post-operatively, but the vast majority (~90%) go on to make a full recovery and experience a good quality of life.

“Fitz” (pictured here recovering from surgery) is a beautiful 3yo male neutered Domestic Shorthair who underwent investigation with our Internal Medicine Specialist, Dr Abigail Brough, and then had surgery with Specialist Surgeon Dr Ben Mielke, to place a SUB in his obstructed right kidney in January 2025. He has gone on to make a complete recovery, and the internal medicine veterinary team are looking forward to seeing him again for his regular SUB flush procedures.