Feline Ureteral Obstruction: Are SUBs the Answer?
Ureteric obstruction is an increasingly common diagnosis in cats and is usually secondary to ureteroliths. Calcium oxalate urolithiasis is the most common cause of the condition. Cats with calcium oxalate urolithiasis have the propensity to form more stones and cats can present with “big kidney little kidney“ syndrome with the larger kidney currently obstructed and the smaller kidney previously obstructed. As a result, these cats often have loss of a large proportion of their nephrons and as such are at risk of chronic renal failure.
Recent management of ureteric obstruction has involved the placement of ureteric stents. These were first described in humans and are currently used for the management of people following ureteroscopy and lithotripsy and following renal transplantation. Previous experience of placing ureteric stents was associated with a relatively high rate of complications in particular dysuria post-operatively.
Therefore, a novel device was developed. The subcutaneous ureteric bypass (SUB) device is an extra-anatomic device, which consists of a pigtail nephrostomy catheter connected to a cystostomy tube via a subcutaneous port.
Pre-operatively, haematology, biochemistry, urinalysis and stabilisation of the cat is performed as routine. Abdominal ultrasound is used to document the obstruction and to measure the size of the renal pelvis; the diameter of the pelvis needs to be more than 5mm to allow the locking loop of the nephrostomy tube to sit in the pelvis. Also, cats who have chronic renal failure and no evidence of an obstruction or renal pelvis dilatation are not candidates and so ultrasound is important for case selection. If there is any doubt in the diagnosis, an antegrade pyelogram can be performed, although it is not performed routinely prior to SUB placement.
Post-operative care is as for any animal with ureteric obstruction whereby fluid ins and outs are monitored. It is not necessary to place urethral catheters unless urine output measurement is essential.
Complications include leakage, tube obstruction and infection. In addition, it is impossible in some cats to detect if there is severe underlying renal failure pre-operatively as the cats are already azotaemic as a result of the obstruction.
We have been placing these devices for 5 years and found initially there was a steep learning curve. Overall, we have found a median survival time of over 500 days and cats have a good quality of life.
BVetMed (Hons) MVetMed CertVDI DipECVS MRCVS European Specialist in Small Animal Surgery
Nicola graduated from The Royal Veterinary College in 2006 and worked for 12 months in general practice. She returned to the RVC in 2007 as Junior Clinical Training Scholar (intern). After another year in practice in Caterham she obtained the position of a Senior Clinical Training Scholar (Resident) in Small Animal Surgery in 2009. Nicola passed the board certifying examination of the European College of Veterinary Surgeons (ECVS) in 2013 and is now a European Specialist in Small Animal Surgery. She has also completed a clinical masters programme (MVetMed) and obtained her certificate in Veterinary Diagnostic Imaging (CertVDI) in 2011.