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.

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.

Subcutaneous ureteral bypass for treatment of proximal ureteral obstruction secondary to retroperitoneal fibrosis after renal transplantation in a cat

Case summary

A 5.5-year-old male neutered domestic shorthair cat was presented with a 2-year history of progressive chronic kidney disease. Abdominal ultrasonography revealed bilateral chronic renal degeneration, nephrolithiasis, cortical hyperechogenicity and infarction. Left orthotopic renal transplantation was performed using the Synovis vascular coupling system for end-to-end anastomosis of the renal arteries and veins. Two months after transplantation, renal values were elevated, and abdominal ultrasonography revealed hydronephrosis and hydroureter of the transplanted kidney. Fluoroscopic antegrade pyelography identified a proximal ureteral stricture. Proximal neoureterocystostomy was performed and renal values normalized postoperatively. The cat was re-evaluated for acute stranguria and severe azotemia 12 months later. Contrast-enhanced CT revealed severe hydronephrosis of the transplanted kidney, obstruction of the proximal ureter and adhesions to the urinary bladder. Upon exploration, retroperitoneal fibrosis was found covering the transplanted kidney. Given the clinical situation, a subcutaneous ureteral bypass device (SUB) was placed. Clinicopathologic analyses, trough cyclosporine levels, aerobic urine cultures and ultrasonographic evaluations of the transplanted kidney were monitored every 1-3 months. Patency of the SUB was reassessed every 3-6 months. At 15 months after placement, the SUB occluded due to kinking of the cystostomy catheter and was replaced. At 28 months after SUB placement, renal function and clinical status deteriorated, and the cat was euthanized.

Relevance and novel information

To the authors' knowledge, this is the first report of a SUB device being used for management of ureteral obstruction in a transplanted kidney in a cat.

Retroperitoneal fibrosis as a postoperative complication following renal transplantation in cats

OBJECTIVES

The aim of this report was to describe the clinical signs, diagnostic imaging findings, surgical management, histopathological findings, outcome and possible risk factors for cats that developed retroperitoneal fibrosis (RPF) following renal transplantation.

METHODS

Medical records of cats that underwent renal transplantation and developed clinically significant RPF between 1995 and 2019 were reviewed.

RESULTS

Eighty-one cats underwent 83 renal transplantations. Of these 81 cats, six developed clinically significant RPF. For all six cats, renal transplantation was performed using cold organ preservation solution and ureteral papilla implantation. Immunosuppression protocol included ciclosporin and prednisolone. All cats had at least one subtherapeutic trough ciclosporin level (<250 ng/ml) in the postoperative period. Cats presented with moderate-to-severe azotemia 39-210 days following renal transplantation. Abdominal ultrasonography and contrast pyelography revealed various degrees of hydroureter and hydronephrosis of the transplanted kidney. Surgical examination revealed a layer of dense fibrous tissue surrounding the transplanted kidney, ureter and bladder resulting in ureteral obstruction. Ureteral obstruction was managed by reimplantation of the proximal ureter or renal pelvis to the bladder. Histopathologic examination of the fibrous tissue and affected portion of the distal ureter revealed fibrous connective tissue with lymphoplasmacytic infiltration and perivascular inflammation suggestive of an autoimmune type reaction. Of the six cats, two died within 5 days after revision surgery, two developed signs consistent with recurrent partial ureteral obstruction (40 and 41 days after revision), one was euthanized 6 years later for an unrelated disease and one was lost to follow-up.

CONCLUSIONS AND RELEVANCE

The incidence of RPF in this population of cats was relatively low (7%), but still represents a significant cause of morbidity and mortality. The cause of RPF remains unknown, although investigation into suboptimal immunosuppression as a potential cause for local rejection reaction is warranted.

Case Report: Imaging Features and Successful Management of Ureteral Stenosis in a Kitten With Bilateral Atypical Papillary Transitional Mucosal Hyperplasia

A 3-month-old cat weighing 2.62 kg was brought to the VIP Animal Medical Center with vomiting, diarrhea, anorexia, and depression. Laboratory findings confirmed azotemia with elevated blood urea nitrogen (BUN) (168.9 mg/dl) and creatinine (5.9 mg/dl) and symmetric dimethylarginine (SDMA) (86 μg/dl). Abdominal radiography revealed bilateral renomegaly. Ultrasonography revealed bilateral hydronephrosis and left partial and right complete ureteral obstructions with bilateral focal irregular and circumferential thickenings at ureters. Reduction of bilateral renal function was confirmed through excretory urography on computed tomography. The cat underwent subcutaneous ureteral bypass surgery on the left kidney, right nephrectomy, and bilateral ureterectomy. Histopathology of bilateral ureteral irregular and circumferential thickening revealed bilateral atypical papillary transitional mucosal hyperplasia. Three days after surgery, the left hydronephrosis resolved, and azotemia was almost resolved. This is the first report of successful management of ureteral stenosis with congenital papillary transitional mucosal hyperplasia in a kitten using multimodality imaging.

Subcutaneous ureteral bypass device placement in 81 cats with benign ureteral obstruction (2013-2018)

Background

Benign ureteral obstructions (BUOs) present a therapeutic challenge in cats.

Hypothesis/Objectives

The purpose of this study was to determine the outcome and complications associated with placement of subcutaneous ureteral bypass (SUB) device in cats.

Animals

Eighty‐one client‐owned cats (117 kidneys) with BUO treated by placement of a SUB.

Methods

Retrospective study. Medical records of cats with BUO and treated by SUB device placement between 2013 and 2018 were reviewed. Outcome and complications were documented.

Results

Hospital discharge rate was 94% (76/81). Serum creatinine on admission and at the time of discharge was 5.3 mg/dL (range, 1.2 to >15 mg/dL) and 2.1 mg/dL (range, 1.1‐12.5 mg/dL), respectively. Luminal obstructions were documented in 17% (18/109) of the SUB devices of 16 cats discharged from the hospital. Infection was documented in 26% (20/76) of discharged cats. Kink of the device was documented in 10% (12/117) of devices. Time to luminal obstruction and kink were 204 days (range, 21‐1678 days) and 58 days (range, 2‐601 days), respectively. Fourteen of 81 (17%) cats required a revision surgery in order to restore patency of the device. At the time of writing, 53% (43/81) of cats were alive, with a mean survival time of 821 days (range, 1‐2170 days) after surgery. Of those that died, 52% (20/38) died of urinary related causes.

Conclusion and Clinical Importance

This study suggests that SUB device placement is associated with good outcomes and could be considered for the treatment of BUO in cats.

Feline abdominal ultrasonography: What's normal? What's abnormal? Renal pelvis, ureters and urinary bladder

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Ultrasound examination of the urinary tract provides important information useful in the investigation of several conditions including ureteral obstruction and cystitis.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even for the experienced ultrasonographer, differentiating between incidental findings, such as lipid droplets in the bladder, and pathological changes can be challenging.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses the ultrasonographic examination of the normal and diseased renal pelvis, ureters and urinary bladder. Aimed at general practitioners who wish to improve their knowledge of and confidence in feline abdominal ultrasound, this review is accompanied by high-resolution images and videos available online as supplementary material. Ultrasound examination of the kidneys and perinephric space was discussed in an article published in May 2020.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although the use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Treatment of congenital distal ureteral orifice stenosis by endoscopic laser ablation in dogs: 16 cases (2010-2014)

OBJECTIVE To determine characteristics of and outcomes for dogs with congenital distal ureteral orifice stenosis (CDUOS) treated by cystoscopic-guided laser ablation (CLA). DESIGN Retrospective case series. ANIMALS 16 client-owned dogs with CDUOS treated by CLA at 2 veterinary hospitals between 2010 and 2014. PROCEDURES Medical records were reviewed and data collected regarding clinical findings, imaging results, surgery characteristics, treatment, and outcome. Follow-up information was collected from dog owners and referring veterinarians via standardized interview. RESULTS Dogs included 10 males and 6 females; median age was 11.5 months (range, 4 to 112 months). Labrador Retriever (n = 6; 3 males) was the most common breed. Intramural ectopic ureteral openings were identified at the site of stenosis in 15 dogs (18/20 stenotic ureteral openings). Treatment with CLA to enlarge and relocate the stenotic opening was successful in all dogs. Median duration of anesthesia and hospitalization was 105 minutes and 24 hours, respectively. No complications were noted. Fourteen dogs remained alive (2 lost to follow-up) during a median follow-up period of 14.5 months. Owners of 11 of 13 dogs reported improvement in their dog's quality of life after CLA. The treated ureteral orifice remained patent in the 2 dogs that were reimaged. CONCLUSIONS AND CLINICAL RELEVANCE CDUOS should be considered as a differential diagnosis for dogs with idiopathic distal ureteral obstruction, particularly young male Labrador Retrievers, and was most often associated with an intramural ectopic ureter in this study. Treatment with CLA was safe and effective for opening the ureteral orifice.

Perioperative morbidity and long-term outcome of unilateral nephrectomy in feline kidney donors: 141 cases (1998-2013)

OBJECTIVE To evaluate the outcome associated with unilateral nephrectomy in feline kidney donors. DESIGN Retrospective case series. ANIMALS 141 cats. PROCEDURES Medical records of cats that underwent nephrectomy for renal donation were reviewed for information on signalment, date of renal donation, results of blood and urine analyses, infectious disease history, anesthetic protocols, intra- and postoperative complications, and postoperative analgesic protocols. Long-term follow-up data were obtained via client telephone interview and review of referring veterinarian medical records. RESULTS All donors were healthy young adult cats with a median age of 1.5 years (range, 0.8 to 2 years). No cats died or were euthanized during the perioperative period. Intraoperative complications occurred in 2 cats, and postoperative complications occurred in 17. Median time from nephrectomy to hospital discharge was 3.6 days (range, 2 to 8 days). Long-term follow-up information was available for 99 cats, with a median interval between nephrectomy and follow-up of 10 years (range, 0.25 to 15 years). Six cats had a history of urinary tract disease including stable chronic kidney disease (n = 3), acute kidney injury (2), and cystitis (1). Nine cats were dead at follow-up; death was attributed to chronic renal failure in 2 and acute ureteral obstruction in 4. CONCLUSIONS AND CLINICAL RELEVANCE Feline donor nephrectomy had an acceptably low perioperative morbidity in this series. Most cats (84%) for which follow-up information was available had no associated long-term effects. However, a small subset (7%) developed renal insufficiency or died of urinary tract disease.