Nephroureteral Obstructions: The Use of Stents and Ureteral Bypass Systems for Renal Decompression

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.

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.

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.

Urolithiasis in dogs: Evaluation of trends in urolith composition and risk factors (2006-2018)

BACKGROUND

Urolithiasis is a common and often recurrent problem in dogs.

OBJECTIVE

To evaluate trends in urolith composition in dogs and to assess risk factors for urolithiasis, including age, breed, sex, neuter status, urolith location, and bacterial urolith cultures.

SAMPLE POPULATION

A total of 10 444 uroliths and the dogs from which they were obtained.

METHODS

The laboratory database at the UC Davis Gerald V. Ling Urinary Stone Analysis Laboratory was searched for all urolith submissions from dogs between January 2006 and December 2018. Mineral type, age, breed, sex, neuter status, urolith location, and urolith culture were recorded. Trends were evaluated and variables compared to evaluate risk factors.

RESULTS

Calcium oxalate (CaOx) and struvite-containing uroliths comprised the majority of all submissions from dogs, representing 47.0% and 43.6%, respectively. The proportion of CaOx-containing uroliths significantly decreased from 49.5% in 2006 to 41.8% in 2018 (P = .006), with no change in the proportion of struvite-containing urolith submissions. Cystine-containing uroliths comprised 2.7% of all submissions between 2006 and 2018 and a significant nonlinear increase in this mineral type occurred over time (1.4% of all submissions in 2006 to 8.7% in 2018; P < .001). Of all cystine-containing uroliths, 70.3% were from intact male dogs. Age, breed, and sex predispositions for uroliths were similar to those previously identified.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although calcium oxalate- and struvite-containing uroliths continue to be the most common uroliths submitted from dogs, a decrease in the proportion of CaOx-containing uroliths and an increase in the proportion of cystine-containing uroliths occurred during the time period evaluated.

Interventions and experience after complicated total cystectomy in a dog with transitional cell carcinoma

OBJECTIVE

To report surgical and postoperative management of complicated total cystectomy in a dog with transitional cell carcinoma (TCC).

STUDY DESIGN

Case report.

ANIMALS

One male neutered Shetland sheepdog.

METHODS

The dog was presented after a 1-month history of stranguria, unresponsive to oral antibiotic therapy. A craniodorsal bladder mass was identified by computed tomography (CT), and partial cystectomy was performed with 1-cm gross lateral margins (day 1). Results of histopathology provided evidence for a diagnosis of TCC, and the dog was treated with adjuvant mitoxantrone. The dog presented with uroperitoneum on day 67 after recurrence and spontaneous perforation. Total cystectomy and ureterourethral anastomosis were performed. Ureteral obstruction developed after removal of catheters that had been placed intraoperatively. Surgical revision included resection of the anastomosis site, bilateral ureteral stenting, and transection and reorientation of the distal urethra to facilitate tension-free closure. Postoperative leakage was managed with bilateral percutaneous nephrostomy tube placement.

RESULTS

The dog was discharged on day 88. Adjuvant treatment with vinblastine was pursued. Local recurrence was noted at day 154. Subcutaneous ureteral bypass was performed on day 247 to manage repeat obstruction. Repeated urinary tract infections were subsequently encountered. The dog was euthanized on day 368 because of abdominal discomfort and inappetence, with evidence of progressive urethral, ureteric, and abdominal wall TCC.

CONCLUSION

Complicated cystectomy can be managed to provide survival comparable to previous reports regarding total cystectomy.

CLINICAL SIGNIFICANCE

Nephrostomy tube placement, ureteral stenting, and subcutaneous ureteral bypass may be considered to manage complicated cystectomy. Preemptive stenting or urinary diversion may help prevent complications.

Permanent Implantable Medical Devices in Exotic Pet Medicine

Medical devices are defined as implantable if they are intended to remain in the body after the procedure. In veterinary medicine, use of such devices is marginal but may find some indications. Use in exotic pet medicine is even more challenging due to size restriction and the limited data available. This review focuses on the esophageal and tracheal stent in the case of stricture, ureteral stent and subcutaneous ureteral bypass in the case of ureteral obstruction, permanent urinary diversion in the case of bladder atony, and pacemaker in the case of severe arrythmias. Comparative aspects are developed.

Use of a subcutaneous ureteral bypass device for treatment of bilateral proximal ureteral injury in a 9-month-old cat

Case summary

A 9-month-old male domestic longhair cat presented following iatrogenic ureteral trauma after an attempted laparoscopic ovariectomy. Prior to identifying that the cat was male, both ureters were transected approximately 4 mm from the renal pelves. Initial management involved a left-sided Boari flap neoureterocystostomy, cystonephropexy and right ureteronephrectomy. Thirty-six hours later, the cat developed uroabdomen due to leakage from the neoureterocystostomy site. At a tertiary referral institution, the ureter was reconstructed via end-to-end anastomosis and a left-sided subcutaneous ureteral bypass (SUB) device was placed in the event the anastomosis failed. Five weeks after SUB placement, the cat was dysuric and stranguric. A urine culture was negative and clinical signs were attributed to sterile cystitis secondary to device placement. Blood urea nitrogen (BUN) was 22 mg/dl and creatinine was 1.2 mg/dl. Contrast pyelography confirmed device patency, but no contrast was identified through the ureteral anastomosis. At 12 months, BUN and creatinine were 1.5 mg/dl and 25 mg/dl, respectively, and a subclinical urinary tract infection was identified (Enterococcus faecalis). Antibiotic therapy was not prescribed in order to prevent multidrug resistance. At 42 months, BUN was 38 mg/dl and creatinine was 2.0 mg/dl. The cat had occasional and intermittent signs of pollakiuria and stranguria but was otherwise doing well.

Relevance and novel information

To our knowledge, this is the first case report to describe the use of a SUB device for management of traumatic proximal ureteral injury in a cat with one kidney. The case outcome provides valuable information about the direct effect of the SUB device and the presence of chronic Enterococcus species infection on long-term renal function.

Ultrasound evaluation of the renal pelvis in cats with ureteral obstruction treated with a subcutaneous ureteral bypass: a retrospective study of 27 cases (2010-2015)

Objectives The objective of the study was to measure the preoperative and postoperative renal pelvic size and describe the ultrasound findings following successful decompression of a ureteral obstruction using the subcutaneous ureteral bypass (SUB) device in cats. Methods This retrospective study assessed the measurement of the renal pelvis of 27 cats with unilateral (n = 21) or bilateral (n = 6) ureteral obstruction before (pre-t0) and after placement of a SUB during short- (before t0 + 3 months) and long-term (after t0 + 3 months) follow-up. Several qualitative ultrasound parameters were recorded for each cat. At both intervals, the last ultrasound examination was used for qualitative criteria and the mean pelvic size was recorded. The complications observed during follow-up were divided into obstructive and non-obstructive. Results No qualitative ultrasound parameter was statistically significant. The presence of retroperitoneal or peritoneal effusion was rarely seen (n = 4/25 during the short term and n = 1/14 during the long term). Hyperechogenicity of the perirenal adipose tissue decreased in the long term. A statistically significant decrease in the width of the renal pelvis was noted in the short- (2.4 mm, range 0-7.0 mm) and long-term (1.7 mm, range 0-3.5 mm) follow-ups compared with the preoperative value (11.7 mm, range 0.9-41 mm). Three months following SUB placement, each cat without an obstructive complication had a pelvic width ⩽3.5 mm. Conclusions and relevance Renal pelvic distension is at least partially reversible when ureteral obstruction is treated by placement of a SUB. Ultrasound monitoring is a useful tool to detect obstructive complications.

Minimally Invasive Management of Uroliths in Cats and Dogs

Urolithiasis commonly affects cats and dogs. The American College of Veterinary Internal Medicine established guidelines for the treatment of uroliths that reflect modern techniques prioritizing minimally invasive procedures with an emphasis on prevention strategies to limit morbidity and mortality. Extracorporeal shockwave lithotripsy and endoscopic nephrolithotomy constitute some of the minimally invasive treatment modalities available for upper urinary tract uroliths. Cystoscopic-guided basket retrieval, cystoscopic-guided laser lithotripsy, and percutaneous cystolithotomy are minimally invasive options for the management of lower urinary tract uroliths. Following stone removal, prevention strategies are essential to help reduce morbidity and mortality associated with stone recurrence.