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Evaluating the results of ureteral surgeries in cats

Wormer C, Clarke DL, Aronson LR.  Outcomes of ureteral surgery and ureteral stenting in cats:  117 cases (2006-2014). J Am Vet Med Assoc 2016;248:518-25.

Feline ureters are small and fragile, and damage to or obstruction of these vital conduits between kidneys and urinary bladder can result in permanent and irreversible impacts on kidney function.  Ureteral surgery, which is technically difficult, is required for animals with congenital abnormalities, trauma, and ureteral obstructions.  Lately, increasing numbers of cats have been diagnosed with obstructive ureterolithiasis, so there is also an increased need for ureteral surgery in this species.

Various techniques have been described for ureteral surgery:  ureteral stenting, subcutaneous ureteral bypass, ureterotomy, neoureterocystostomy.  Significant perioperative complication rates and perioperative mortality rates for ureterotomy and neoureterocystostomy in cats have been reported in the literature.  Many surgeons now have a preference for ureteral stenting because it is perceived as being less invasive and having fewer complications than ureterotomy or neoureterocystostomy, yet will accomplish the same results.  Ureteral stenting, however, is also not without complications, including stent migration, chronic urinary tract infections, signs of lower urinary tract discomfort, and accumulation of and crusting of the stent with particulate debris.  Subcutaneous urethral bypass surgery (SUB) is another technique that has been developed recently, but information regarding long-term efficacy and complications with SUB is limited.

This retrospective case series of 117 cats undergoing various types of ureteral surgeries (ureterotomy, neoureterocystostomy, and ureteral stent placement) at a veterinary teaching hospital in the USA reports on perioperative complication rates, mortality rates, and short-term and long-term outcomes in these patients.  Some of the animals required bilateral ureteral surgery, while in others, the surgery was unilateral; board-certified surgeons either personally performed or supervised all surgeries.  Domestic shorthair cats comprised 76% (89/117) of the patients; 9% (11/117) were domestic longhairs, and the rest represented a variety of pedigreed breeds.  The median age of the patients was 8 years (range 1-17 years).  Half of the cats (51%) were neutered males; 49% were females (55 spayed and 2 intact).

Common clinical signs of ureteral disease in these cats included inappetence (45/117; 38%), lethargy (32/117; 27%), signs of lower urinary tract disease (27/117; 23%), vomiting (17/117; 15%), and weight loss (17/117; 15%), and there were multiple signs in some cats.  Of the 117 cases, 46 (39%) had undergone previous medical management of urinary tract disease prior to referral to the teaching hospital.  Previously diagnosed and treated urinary tract diseases in these patients included chronic kidney insufficiency (24/117; 21%), urethral obstruction (8/117; 7%); acute kidney injury (2/117; 2%), polycystic kidney disease, renal agenesis, idiopathic cystitis, or ureteral obstruction due to ureteroliths (each 1/117; 0.9%). Of the 117 patients, five had had previous urinary tract surgery (cystotomy for cystolith removal, ureterotomy for ureterolith removal, ureteronephrectomy for renal carcinoma, and ureteronephrectomy for pyelonephritis).

Clinicopathologic findings included azotemia in 86/117 cats (74%), anemia in 79/117 (68%), hyperphosphatemia in 39/117 (33%), and hyperkalemia in 23/117 (20%).  The majority of the cats had a urine specific gravity <1.012 (72/117; 62%).  A microbial urine culture was obtained in 95/117 (81%) of the patients, and 30 of these animals had a positive bacterial urine culture.  Escherichia coli was far and away the most common pathogen cultured, found in 87% of cats with urinary tract infections. The median systolic blood pressure obtained by Doppler was 140 mm Hg (range 90-190 mm Hg), and 26/117 cats (22%) had readings > 150 mm Hg, which the authors define as hypertensive.  A cardiac murmur was ausculted in 63/117 (54%) of the cats, and 14 of these animals were found to have cardiomyopathy upon echocardiographic evaluation.  Almost all of the cats (115/117) were evaluated with abdominal ultrasonography prior to surgery, and about half (63/117; 54%) also had pre-surgical abdominal radiographs; a few also had contrast urography or abdominal CT scans.

Most of the patients (102/117; 87%) had ureterolithiasis; 10/117 (9%) had focal ureteral strictures at the level of the urinary bladder trigone.  There were bilateral ectopic ureters in one cat, and another had bilateral distal ureteral obstruction secondary to neoplasia.  Two of the cats had iatrogenic ureteral transection during ovariohysterectomy following dystocia.  Nephroliths, renal mineralization, and chronic renal changes were noted in 38/117 (32%), 21/117 (18%), and 85/117 (73%) of the patients, respectively.

All of the cats received IV fluids and antimicrobials prior to surgery.  Most cats (69/117; 59%) had a single ureterotomy incision on the left ureter (32/117), right ureter (27/117), or both ureters (10/117). Three of the cats required multiple ureterotomies.  All ureterotomies were performed to remove ureteroliths, and in 63 of the cats undergoing ureterotomies, no stents were placed.  Neoureterocystostomy was performed in 12/117 (10%) of the patients; 10 of these surgeries were unilateral, and 2 were bilateral, and only one cat undergoing this procedure received a stent.  Ureteral stents were placed in 43/117 (37%) of patients; 37 of these were unilateral, and 6 were bilateral.  The stents were used in conjunction with ureterotomy in 9 cats, in one cat undergoing neoureterocystostomy, and in 33 animals as sole treatment for ureteral obstruction.  The majority of the animals had other surgical procedures along with the ureteral surgery, mostly cystotomy (76), esophagostomy feeding tube placement (17), nephrostomy tube placement (5), perineal urethrostomy (3), gastrointestinal biopsy (2), renal biopsy (1), and cystopexy (1).  A packed red blood cell transfusion was given to 44/117 (38%) patients perioperatively.

Based on the above data, a large number of these patients had concurrent diseases and abnormal clinicopathologic findings, which could predispose them to significant perioperative complications and mortality, as well as poorer short- and long-term outcomes than otherwise healthy patients.  Uroabdomen was the most common complication that occurred (8/117; 7%) in these cats.  In 6/8 of the cats with uroabdomen, the urine leakage resolved with conservative treatment, which involved urinary catheter placement to keep the urinary bladder decompressed.  Two of the 43 cats (5%) who received ureteral stents experienced migration of the stent, and in both cases, surgery was performed to correct this.  Congestive heart failure due to volume overload (n = 4), pancreatitis (n =3), hepatic lipidosis (n =3), and sepsis (n =2) were other complications reported; all of these problems developed postoperatively, and all resolved with medical treatment.

Ten of the 117 patients (9%) did not survive to hospital discharge; 4/10 had ureteral stent placement.  Perioperative mortality rate did not differ for cats receiving ureteral stents from those not receiving stents in conjunction with ureterotomy or neoureterocystostomy.  Seven of these cats were euthanized due to progressive renal failure, and one was euthanized because of uroabdomen.  The other two cats died from respiratory distress of unknown etiopathogenesis.

Of the 107 cats that survived to hospital discharge, follow-up information was available for only 87.  Median follow-up time was 742 days (range 34-2,800 days).  Over half of the patients (48/87; 55%) were still alive at last follow-up. The surgical treatment modality did not have any significant effect on survival time.  Out of the 87 cats with follow-up information, there was a high incidence of ureteral reobstruction (19/87; 22%), also regardless of surgical technique.

A substantial number of cats in the study had signs of lower urinary tract disease unrelated to infection (17/87; 20%) and chronic lower urinary tract infection (10/87; 11%) during the follow-up period.  These lower urinary tract diseases were significantly more common in those cats who received stents than in those that did not.  This is also found to be true in humans, and in people, infections are attributable to bacterial colonization of the stents and subsequent biofilm formation.  The authors counsel clinicians to consider the possibility of implant-related urinary tract infections in patients for whom they are considering stent placement or SUB surgery, and to discuss this possibility and potential further complications such as the necessity for implant replacement or removal.

When there was recurrent upper urinary tract obstruction in the patients, it was usually caused by recurrent urethrolithiasis (14/19 cats with ureteral reobstruction) , but urethral stricture and ureteritis were also reported.  Given the high incidence of ureteral reobstruction noted in the study population, the authors recommend regular post-treatment follow-up, including abdominal imaging, regardless of the treatment modality utilized.

Twenty-five of the 87 cats (29%) for whom follow-up information was available ultimately died of progressive renal failure; owners should be advised to be prepared for a guarded long-term prognosis following ureteral surgery; this may be especially true in cats with pre-existing chronic renal disease. In this and other studies, chronic renal disease has been found to be common in cats with obstructive ureterolithiasis.  The authors speculate that cats with chronic kidney disease may be more susceptible to kidney injury secondary to obstruction by nephroliths or ureteroliths and acute renal failure than cats without chronic kidney disease.

This study was retrospective, and a number of patients (20/107) that survived to hospital discharge were lost to follow-up.  Given the variety of urinary tract diseases and other concurrent health conditions in the patients, the fact that pre- and postoperative treatments were not standardized, that the choice of surgical procedure used was based on clinician preference, and that surgeon experience with ureteral surgeries varied, results of this study are most likely somewhat confounded.  The authors recommend a prospective, randomized study that would compare ureteral surgical techniques to give further insight as to which technique might most benefit feline patients with particular ureteral disease problems. [PJS]

See also:
Palm CA, Culp WTN.  Nephroureteral obstructions: the use of stents and ureteral bypass systems for renal decompression.  Vet Clin Small Anim 2016;46(6):1183-92.

Horowitz C, Berent A, et al.  Predictors of outcome for cats with ureteral obstructions after interventional management using ureteral stents or a subcutaneous ureteral bypass device. J Feline Med Surg 2013;15:1052-62.