Survival and complications in cats treated with subcutaneous ureteral bypass

Medical and Surgical Management of Ureteral Obstructions

Many patients with ureteral obstructions are critically ill at the time of diagnosis, especially if there is dysfunction of the contralateral kidney. They may present with varying severities of uremia and acute kidney injury as well as systemic inflammation and sepsis secondary to infection. Medical management, which may consist of rehydration and restoration of intravascular volume with intravenous fluid therapy, osmotic diuresis, ureteral muscle relaxation, and antimicrobials for infection, is important in ureteral obstruction patients. Unstable patients may require more emergent intervention to relive the obstruction and address the life-threatening sequelae to acute kidney injury.

Assessing Ureteral Patency by Fluoroscopy and Ultrasonography After Subcutaneous Ureteral Bypass Device Placement for the Treatment of Benign Ureteral Obstruction in Cats

BACKGROUND

Limited information on the patency of native ureters after subcutaneous ureteral bypass (SUB) device placement is available.

OBJECTIVE

Evaluate the patency of native ureters in cats treated with SUB device placement for benign ureteral obstruction.

ANIMALS

Cats with SUB presented for routine evaluation.

METHODS

Routine ultrasound-guided SUB irrigations were performed, focusing on ureteral irrigation in the trigone and proximal urethra. Cats with obstructed nephrostomy catheters or subcutaneous ports were excluded. Fluoroscopic-guided SUB irrigations with iodinated contrast then were used to assess patency. Ureters were deemed patent if contrast filled the lumen evenly along their length, and obstructed if the contrast column was interrupted on consecutive images. Intraoperative fluoroscopy was reviewed to confirm the cause and location of the obstructions.

RESULTS

Overall, 18 cats (18 SUBs; 10 unilateral, 8 bilateral) were included. The causes of obstruction were ureteroliths (23 ureters) and presumed stricture (3 ureters). A trigonal irrigation was visible in 14/18 cats (77%; 95% confidence interval [CI]: 54.8%-91.0%); the patent side in bilateral SUBs could not be differentiated. Three ureters were excluded (nondiagnostic study, n = 1; obstructed nephrostomy, n = 2). Of the remaining 23 ureters, 19 (82.6%; 95% CI: 62.9%-93.0%) were patent: 16/20 patent ureters were obstructed with ureteroliths (80%; 95% CI: 58.4%-91.9%) and 3/3 with presumed stricture (100%; 95% CI: 43.9%-100%). Ureteral irrigations at the trigone were associated with patency.

CONCLUSIONS

A high patency rate of native ureters after SUB placement was observed. Ureteral irrigations at the trigone reliably indicate patency. Supraphysiologic SUB irrigations may result in underdiagnosed persistent partial obstructions.

Case Report: Long-term complications of subcutaneous ureteral bypass migration in an adult female Papillon

A 6-year-old spayed female 4.4-kg Papillon with only the left kidney presented with vomiting. Imaging unveiled ureterolithiasis and hydronephrosis, while serum chemistry displayed elevated creatinine, blood urea nitrogen, and C-reactive protein. Urinalysis revealed bacteria and bacterial phagocytes. After subcutaneous ureteral bypass (SUB) placement, kidney panels were normalized. The nephrostomy and cystostomy catheters had migrated into the renal parenchyma and bladder wall on postoperative day (POD) 212 and 369, respectively. As the migration advanced, they entered the ureter and bladder on POD 369 and 796, respectively. The SUB, excluding the nephrostomy catheter, was removed on POD 930 due to migration, obstruction, and extrusion of the SUB shunting port. On POD 937, creatinine and BUN levels remained normal. By POD 1063, the ureteroliths had disappeared. This case highlights the need for vigilant monitoring of catheter migration as a potential complication following SUB placement. Early identification and timely intervention are essential for reducing morbidity and improving patient outcomes.

Association of preoperative ultrasonographic parameters of the contralateral kidney with long-term serum creatinine in cats treated for unilateral ureteral obstruction

Introduction

Prediction of renal recovery after surgical management of feline unilateral ureteral obstruction (UO) is crucial to guide therapeutic decisions, but predictors of this outcome are still lacking. Despite the functional importance of the contralateral kidney, there is currently no precise description of its ultrasonographic (US) features. In addition, US parameters of both the renal collecting system and the renal parenchyma have been identified in human medicine as prognostic factors in the case of UO but have not been described in veterinary medicine. The aim of this study was to evaluate an association between preoperative structural US renal parameters and long-term International Renal Interest Society (IRIS) stage after successful renal decompression with subcutaneous ureteral bypass (SUB) device in cats with unilateral UO.

Methods

This retrospective study included 60 cats with unilateral UO and evaluated preoperative US parameters of both kidneys, including measurements of parenchymal and pelvic areas as well as a renal score. Cats were divided according to their serum creatinine at 3 months postoperatively into group A (IRIS stages I and II) and group B (IRIS stages III and IV).

Results

A higher US chronic kidney disease (US-CKD) score of the kidney contralateral to the UO was associated with long-term IRIS stages III and IV. It also appeared as a fair discriminator of long-term IRIS stage IV, with an area under the curve of 0.74. The optimal cutoff value for accurately identifying cats with long-term IRIS stage IV was a US-CKD score > 7, with a specificity of 98%, a sensitivity of 25%, and a positive likelihood ratio of 12.75. No preoperative US parameters regarding the obstructed kidney, including parenchymal and pelvic areas, were significantly associated with long-term creatinine.

Conclusion

Ultrasonographic scoring of contralateral chronic kidney disease abnormalities is associated with IRIS stage following treatment of feline unilateral UO with a SUB device and serves as a specific indicator of cats presenting with long-term IRIS stage IV.

Use of the subcutaneous ureteral bypass device and urethral stenting for treatment of malignant urinary outflow tract obstructions in cats

OBJECTIVES

The aim of this study was to describe the technical success and outcomes of ureteral and urethral decompression using the subcutaneous ureteral bypass (SUB) device and transurethral self-expanding metallic stents (SEMS) as a palliative treatment option for feline malignant urinary outflow tract obstructions.

METHODS

A retrospective study was conducted of 14 cats with ureteral and/or urethral obstructions secondary to diagnosed or suspected transitional cell carcinoma (TCC). In all cats, a SUB device and/or a SEMS was placed to relieve the obstruction(s). Group 1 consisted of cats with ureteral obstructions, with or without concurrent urethral obstructions, and group 2 consisted of cats with only urethral obstructions.

RESULTS

Eight cats were included in group 1 (seven with concurrent urethral obstructions) and six cats were included in group 2. TCC was confirmed in 8/14 cats. Repeat urethral obstruction due to tumor in growth occurred in 6/13 (46%) cats with a SEMS, and no cats developed recurrent ureteral obstructions after placement of the SUB device. Three cats had additional covered stents placed after urethral re-obstruction. The median survival time (MST) from the time of device placement was 52 days in group 1 (mean 92; range 14-349) and 80 days in group 2 (mean 96; range 7-209). The MST from the time of mass identification of the cats that did and did not receive adjunctive therapy was 349 days (mean 358; range 124-602) and 43 days (mean 113; range 14-423), respectively.

CONCLUSIONS AND RELEVANCE

The use of bypass devices for feline malignant urinary outflow tract obstructions is a viable option to provide immediate renal and urinary bladder decompression. TCC in cats is locally aggressive and can result in urethral re-obstruction, prompting consideration for placing a covered urethral stent. The use of adjunctive therapies for malignant neoplasia should be considered to improve overall survival once the obstruction has been relieved.

Surgical repositioning with omentalisation of an exposed subcutaneous ureteral bypass shunting port in a cat

Case summary

A 9-year-old, spayed, female domestic shorthair cat presented with an open wound approximately 1 cm in size with exposure of the left subcutaneous ureteral bypass (SUB) shunting port that was placed approximately 11 months before presentation. Primary closures were attempted twice before local wound management with omentalisation and repositioning of the port. The exposed port was lavaged topically with a polyhexanide and propylbetaine wound irrigation solution before omentalisation and repositioning, resulting in successful retention of the implant. Five months after revision and omentalisation, there was complete coverage and healing of the wound.

Relevance and novel information

Adequate topical treatment, repositioning and omentalisation could be a successful treatment option for the uncommon complication of SUB shunting port extrusion secondary to resistant local infection originating from the urinary tract.

Analysis of lower urinary tract signs and bacteriuria in cats with subcutaneous ureteral bypass systems

Objectives

Distinguishing bacterial cystitis from subclinical bacteriuria is necessary for feline treatment protocols and antimicrobial stewardship. This can be challenging in cats with subcutaneous ureteral bypass (SUB) systems because they may present with lower urinary tract signs without bacteriuria. We investigated the relationship between positive urine culture and lower urinary tract signs in cats with SUBs, including factors associated with each.

Methods

Clinical records were retrospectively reviewed to identify cats presenting with ureteral obstruction that underwent placement of a SUB device(s). The relationship between a positive urine culture and lower urinary tract signs was determined by chi-squared analysis. Univariable and multivariable logistic regression models were performed to identify factors associated with positive urine cultures and lower urinary tract signs.

Results

Two hundred and thirty visits were recorded for 61 cats, with 36 of 230 (16%) positive cultures in 21 of 61 (34%) cats. Lower urinary tract signs were documented at 97 of 230 (42%) visits, with 37 of 61 (61%) cats demonstrating lower urinary tract signs at some point. No relationship was found between culture results and lower urinary tract signs. Risk factors for a positive culture were higher urine pH, higher urine white blood cells and the presence of bacteriuria on microscopy. Risk factors for lower urinary tract signs were younger age and being a purebred cat (vs. non-purebred).

Conclusions

A high proportion of cats with SUBs exhibited sterile lower urinary tract signs, making differentiation between bacterial cystitis and subclinical bacteriuria difficult. This highlights the need for clearer guidelines on when to treat bacteriuria in cats with SUBs.

Extravesicular, two-layer, side-to-side ureteroneocystostomy combined with tension-relieving techniques for feline proximal ureteral obstruction: A retrospective study

OBJECTIVE

To describe the surgical technique for extravesicular, two-layer, side-to-side ureteroneocystostomy combined with tension-relieving techniques (ETSUTT) for feline proximal ureteral obstruction and report clinical outcomes.

STUDY DESIGN

Retrospective case series.

ANIMALS

Ten privately-owned cats with ureteral obstruction near the ureteropelvic junction (UPJ).

METHODS

Medical records were retrospectively reviewed for cats with ureteral obstruction close to the UPJ that underwent ETSUTT (2018-2021). The ETSUTT procedure consisted of a modified extravesicular technique (two-layer, side-to-side ureteroneocystostomy) and tension-relieving techniques (renal descensus, ureterocystopexy, and nephrocystopexy).

RESULTS

All cats survived through discharge. In all cats, postoperative blood urea nitrogen and creatinine concentrations were decreased, compared with preoperative concentrations. Perioperative complications included ureteral catheter dislodgement (3), transient pollakiuria (2), and dysuria (1), but no specific treatments were required. Urinary tract infection was observed postoperatively in three of the 10 cats. The median follow-up was 648 days (min-max: 86-1229 days). Seven of the 10 cats were alive without recurrent ureteral obstruction at the end of this retrospective study.

CONCLUSION

The ETSUTT procedure was successfully performed without major complications in cats with ureteral obstruction occurring near the UPJ. Use of ETSUTT provided a fair-to-good, long-term prognosis in cats that were otherwise difficult to manage.

CLINICAL SIGNIFICANCE

This novel procedure, ETSUTT, was feasible, safe, and could be a viable treatment option for feline proximal ureteral obstruction, including the UPJ, especially for obstructions caused by stricture.

Development of a burst wave lithotripsy system for noninvasive fragmentation of ureteroliths in pet cats

BACKGROUND

Upper urinary tract stones are increasingly prevalent in pet cats and are difficult to manage. Surgical procedures to address obstructing ureteroliths have short- and long-term complications, and medical therapies (e.g., fluid diuresis and smooth muscle relaxants) are infrequently effective. Burst wave lithotripsy is a non-invasive, ultrasound-guided, handheld focused ultrasound technology to disintegrate urinary stones, which is now undergoing human clinical trials in awake unanesthetized subjects.

RESULTS

In this study, we designed and performed in vitro testing of a modified burst wave lithotripsy system to noninvasively fragment stones in cats. The design accounted for differences in anatomic scale, acoustic window, skin-to-stone depth, and stone size. Prototypes were fabricated and tested in a benchtop model using 35 natural calcium oxalate monohydrate stones from cats. In an initial experiment, burst wave lithotripsy was performed using peak ultrasound pressures of 7.3 (n = 10), 8.0 (n = 5), or 8.9 MPa (n = 10) for up to 30 min. Fourteen of 25 stones fragmented to < 1 mm within the 30 min. In a second experiment, burst wave lithotripsy was performed using a second transducer and peak ultrasound pressure of 8.0 MPa (n = 10) for up to 50 min. In the second experiment, 9 of 10 stones fragmented to < 1 mm within the 50 min. Across both experiments, an average of 73-97% of stone mass could be reduced to fragments < 1 mm. A third experiment found negligible injury with in vivo exposure of kidneys and ureters in a porcine animal model.

CONCLUSIONS

These data support further evaluation of burst wave lithotripsy as a noninvasive intervention for obstructing ureteroliths in cats.

Modified endoluminal ureteral stenting for the management of proximal ureteral obstruction in two cats

Case series summary

Two cases of placement of modified endoluminal ureteral stents are described, for revision of a subcutaneous ureteral bypass (SUB) and for primary treatment of obstructive ureterolithiasis. Modified endoluminal stents were inserted through the ureterotomy, anchored in the renal pelvis with a single pigtail and shortened to a length sufficient to span the proximal ureter and ureterotomy site.

Relevance and novel information

The advantages of this approach as a surgical option for feline obstructive ureterolithiasis are demonstrated, including the avoidance of disruption, or bypass, of the ureterovesicular junction, minimisation of implanted foreign material and avoidance of intravesicular stent mass, maintenance of the physiological route of urine flow, including preservation of active distal ureteral function, and limitation of the potential complications of ureterotomy. The clinical efficacy of this adaptation of the previously published endoluminal stenting technique is demonstrated with its applicability de novo and in the revision of other stenting procedures.

Urinary Tract Trauma in Cats: Stabilisation, Diagnosis and Management

PRACTICAL RELEVANCE

Traumatic injury of the urinary tract may be caused by external accidental trauma or due to iatrogenic injury (typically as a result of catheterisation procedures). Thorough patient assessment and careful attention to patient stabilisation are essential, with diagnosis and surgical repair delayed until the patient is stable, if necessary. Treatment depends on the location and severity of the trauma. If diagnosed and treated promptly, the chance of survival of a patient without other concurrent injuries is good.

CLINICAL CHALLENGES

Following accidental trauma, at the initial presentation urinary tract injury can be overshadowed by other injuries, but if left undiagnosed or untreated it can lead to serious morbidity and potentially mortality. Many of the surgical techniques described for management of urinary tract trauma can be associated with complications, and so comprehensive communication with the owners is necessary.

PATIENT GROUP

The main population affected by urinary tract trauma is young, adult male cats, owing to their roaming behaviour, as well as their anatomy and the resulting increased risk of urethral obstruction and its associated management.

AIMS

This article aims to serve as a guide to all veterinarians who treat cats for the diagnosis and management of urinary tract trauma in cats.

EVIDENCE BASE

This review summarises the current knowledge available from a number of original articles and textbook chapters in the literature that cover all aspects of feline urinary tract trauma, and is supported by the authors' own clinical experience.

Risk factors for upper urinary tract uroliths and ureteral obstruction in cats under referral veterinary care in the United Kingdom

BACKGROUND

Cats presenting with upper urinary tract uroliths (UUTUs) and ureteral obstruction ("obstructive UUTU") are typically younger than cats with idiopathic CKD that often have incidental nephroliths.

HYPOTHESIS

Cats with upper urinary tract urolith have 2 clinical phenotypes; a more aggressive phenotype at risk of obstructive UUTU at a young age and a more benign phenotype in older cats, with reduced risk of obstructive UUTU.

OBJECTIVES

Identify risk factors for UUTU and for obstructive UUTU.

ANIMALS

Eleven thousand four hundred thirty-one cats were referred for care over 10 years; 521 (4.6%) with UUTU.

METHODS

Retrospective VetCompass observational cross-sectional study. Multivariable logistic regression models were performed to identify risk factors for a diagnosis of UUTU vs no UUTU and additionally, obstructive UUTU vs nonobstructive UUTU.

RESULTS

Risk factors for UUTU included female sex (odds ratio [OR] 1.6, confidence interval [CI] 1.3-1.9; P < .001), British shorthair, Burmese, Persian, Ragdoll or Tonkinese (vs non-purebred ORs 1.92-3.31; P < .001) breed and being ≥4 years (ORs 2.1-3.9; P < .001). Risk factors for obstructive UUTU were female sex (OR 1.8, CI 1.2-2.6; P = .002), having bilateral uroliths (OR 2.0, CI 1.4-2.9; P = .002) and age, with the odds of obstructive UUTU increasing as age at diagnosis of UUTU decreased (≥12 years, reference category; 8-11.9 years, OR 2.7, CI 1.6-4.5; 4-7.9 years, OR 4.1, CI 2.5-7.0; 0-3.9 years, OR 4.3, CI 2.2-8.6; P < 0.001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Cats diagnosed with UUTU at a younger age have a more aggressive phenotype with higher risk of obstructive UUTU compared to cats over 12 years of age diagnosed with UUTU.

Antegrade CT pyelography of right retrocaval ureter causing ureteral stenosis and ureterohydronephrosis in an exotic shorthair cat: A case report

Retrocaval ureter is a rarely reported congenital malformation of the caudal vena cava in veterinary medicine. In this report, a 2-year-old exotic shorthair cat weighing 3.4 kg was presented for depression and loss of appetite. Laboratory findings was unremarkable. Abdominal radiography revealed right renomegaly, and ultrasonography suggested right ureterohydronephrosis. Right retrocaval ureter was recognized by computed tomography. An antegrade pyelography was performed to identify the localization of obstruction and whether obstruction was complete or partial. Complete right ureteral stenosis was confirmed through right antegrade pyelography on computed tomography. The cat underwent right nephroureteroectomy and recovered well after surgery. This is the first report of successful diagnosis and treatment of retrocaval ureter in a cat with significant clinical and imaging signs, using ultrasonographically guided percutaneous antegrade pyelography and multimodal imaging such as radiography, ultrasonography, and computed tomography.

Multicenter retrospective evaluation of transmural migration of subcutaneous ureteral bypass devices within the digestive tract in catsone

BACKGROUND

Placement of a subcutaneous ureteral bypass (SUB) device is an effective method to relieve all causes of ureteral obstruction in cats. Complications involving migration within the gastrointestinal tract have been seldomly described.

OBJECTIVES

To characterize transmural migration of SUB devices within the digestive tract in cats.

ANIMALS

Eleven migrated SUB catheters identified in 8 cats between 2017 and 2021.

METHODS

Retrospective review of medical records of cats with a SUB device in which migration into the gastrointestinal tract was identified.

RESULTS

The median time from SUB device placement to implant migration was 928 days (201-2298 days). Seven cats had obstruction of the SUB device and a positive urine culture at diagnosis. The migration was identified by ultrasound in 6/11, pre-operative contrast radiography in 2/2, and only at time of surgery in 3 SUB devices. All cats underwent surgical correction. Four nephrostomy and 7 cystotomy catheters migrated. Migration occurred into the duodenum (3/11), jejunum (7/11), and colon (1/11). SUB devices were removed in 7 cats and replaced in 2 cats, with 1 cat diagnosed with 2 migration events. Gastrointestinal resection and anastomosis were performed in 7/8 cats and an enterotomy in 2 cats. Six cats survived to discharge. The median follow-up time after migration diagnosis was 365 days (range, 0-1114 days) and 2 cats are still alive.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although a rare complication, migration of SUB device should be considered in cats with SUB device obstruction and a positive urine culture.

Transmural migration of a subcutaneous ureteral bypass into the intestine in three cats

Subcutaneous ureteral bypass™ is a device placed in cats with ureteral obstruction. The most common complications include system occlusion, urinary tract infection and sterile cystitis. In this case series, we describe three cats with subcutaneous ureteral bypass devices placed where transmural migration of subcutaneous ureteral bypass catheters into the small intestine resulted in gastrointestinal signs, urinary infection and subcutaneous ureteral bypass occlusion. The system was changed in one case and removed in the other two. In all cases, an intestinal resection and anastomosis was performed. All cats had a good medium-term outcome, and urinary infection persisted in the case for which the subcutaneous ureteral bypass system was changed. Transmural migration of the device should be ​considered in cats with subcutaneous ureteral bypass presenting with persistent urinary tract infection, gastrointestinal signs or device obstruction, even if imaging studies such as ultrasound or contrast studies do not demonstrate any abnormalities.

Feline ureteral obstruction: a case-control study of risk factors (2016-2019)

OBJECTIVES

Ureteral obstruction (UO) in cats causes acute kidney injury and typically requires surgical intervention. Information is required about potentially modifiable risk factors to inform prevention strategies.

METHODS

A case-control study was performed to assess risk factors associated with feline UO. Cases were defined as cats with either of the following: (1) ureteral obstruction (ureteroliths: 13/18; unknown: 5/18) confirmed with pyelography; or (2) a creatinine concentration >140 µmol/l with both UO (ureteroliths: 6/10; blood clots: 3/10; pyonephrosis: 1/10) and pyelectasia ⩾5 mm on abdominal ultra sonography. Controls were defined as cats without evidence of UO on history, physical examination and abdominal ultrasound. Age, sex, breed (domestic shorthair/longhair), diet (predominantly dry, mixed or predominantly moist food), housing (indoors or mixed) and plasma total calcium were evaluated for their association with UO using multivariable logistic regression. A receiver operator characteristic (ROC) curve was created to evaluate the predictive ability of the final model.

RESULTS

In total, 168 cats (28 cases, 140 controls) were included. Age, sex, breed, housing and total calcium were not significantly associated with UO; however, diet was. Compared with cats eating a predominantly moist food diet, cats fed a predominantly dry food diet were 15.9 times more likely to develop a UO (95% confidence interval 2.9-295; P = 0.009). There was no difference in the association between diet and UO in cats fed a mixed diet vs cats fed a predominantly moist food diet (P = 0.25). The area under the ROC curve was 72%.

CONCLUSIONS AND RELEVANCE

Changes in diet formulation could provide a simple and economical method to reduce the risk of UO.

Complications and survival after subcutaneous ureteral bypass device placement in 24 cats: a retrospective study (2016-2019)

OBJECTIVES

The aim of this study was to document survival, complications and risk factors for the development of complications and mortality prior to discharge after placement of a subcutaneous ureteral bypass (SUB) device in cats.

METHODS

The medical records of cats with SUB placement between January 2016 and August 2019 were retrospectively analysed. The development of complications (overall, intraoperative, perioperative, short- and long-term complications) and risk factors for mortality prior to discharge were statistically assessed with univariate binary logistic regression. All variables with a P value ⩽0.10 in the univariate analysis were assessed in a multivariate model. Variables were significant if P <0.05.

RESULTS

Twenty-four cats were included; 12 (50.0%) received a unilateral SUB, 11 (45.8%) a bilateral nephrostomy tube with single cystostomy catheter and the remaining cat (4.2%) two unilateral SUBs. Nearly 80% of the cats developed complications, ranging from mild to fatal, including (partial) SUB obstruction (33.3% of complications), lower urinary tract infection (20.8%), pyelonephritis (20.8%) and sterile cystitis (12.5%). Five cats (20.8%) died prior to discharge. Six cats (25.0%) underwent revision surgery. The overall median survival time (MST) was 274 days (range 1-311 days). Complications were most common in the long-term period (14/16 cats), followed by the short-term (9/18 cats), perioperative (10/23 cats) and intraoperative (4/24 cats) periods. Older cats had an increased risk for developing perioperative complications (P = 0.045) and were less likely to survive to discharge (P = 0.033). An increased haematocrit at presentation was a risk factor for the occurrence of short-term complications (P = 0.03).

CONCLUSIONS AND RELEVANCE

Although complications similar to those previously described were observed, the complication rate was higher and the MST shorter than previously reported in cats undergoing SUB placement. Despite good short-term survival, the development of complications may necessitate regular and intensive control visits. Owners that consider SUB placement should be informed that follow-up can be strenuous and expensive.