Diagnostic imaging observations in cats treated with the subcutaneous ureteral bypass system

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.

Use of tetrasodium EDTA acid for the treatment of intraluminal obstruction of subcutaneous ureteral bypass devices

OBJECTIVES

The aim of this study was to evaluate the efficacy and tolerability of a 4% tetrasodium EDTA (tEDTA) infusion protocol in the subcutaneous ureteral bypass (SUB) devices of cats with intraluminal obstruction at a veterinary teaching hospital between July 2017 and April 2020.

METHODS

This was a retrospective controlled study. Cats with an obstructed SUB device underwent a 4% tEDTA infusion protocol. Obstruction of the device was diagnosed based on renal pelvic dilation, dilatation of the ureter, mineralized material within the device (cystostomy or nephrostomy catheters) seen on ultrasound, the absence of visible bubbles within the renal pelvis and/or urinary bladder following ultrasound-guided flushing of the device with saline.

RESULTS

A total of 16 tEDTA infusion protocols were performed in 14 cats. The infusion protocol was considered successful in 11/16 SUB devices (68.8%). Six devices (n = 6/11; 54.5%) had recurrence of obstruction with a median time of 87 days. One or more episodes of self-limiting pollakiuria and/or hematuria following infusion was seen in eight patients (n = 8/14; 57.1%).

CONCLUSIONS AND RELEVANCE

Infusions of 4% tEDTA successfully relieved intraluminal obstruction in patients with occluded SUB devices; however, the recurrence of obstruction was common. Additional studies evaluating case selection and optimal protocols are warranted.

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.

Comparison of nonenhanced computed tomography and ultrasonography for detection of ureteral calculi in cats: A prospective study

BACKGROUND

Radiographs and ultrasound (US) are the primary imaging modalities used to assess ureteral calculi in cats. Reports describing the use of nonenhanced computed tomography (CT) are scarce.

HYPOTHESIS/OBJECTIVES

To compare US and nonenhanced CT for detection, number and localization of ureteral calculi in cats.

ANIMALS

Fifty-one cats with at least 1 ureteral calculus, and 101 ureters.

METHODS

Prospective case series. All cats underwent an US followed by a nonenhanced CT. Cats were included in the study if at least 1 ureteral calculus was diagnosed on either modality. Number of calculi and their localization (proximal, middle, and distal) were recorded on both modalities. Pelvic dilatation and maximal ureteral diameter were recorded with US.

RESULTS

More calculi were detected by nonenhanced CT (126) compared to US (90), regardless of localization (P < .001). More ureters were affected on nonenhanced CT (70) compared to US (57; P < .001). The number of calculi detected was significantly different between US and nonenhanced CT in the proximal (P = .02) and distal ureteral region (P < .001). Bilateral calculi were more frequent with nonenhanced CT (19 cats) compared to US (9 cats; P < .001). A pelvic size superior to 5 mm and a maximal ureteral diameter value superior to 3 mm were always associated with ureteral calculi.

CONCLUSIONS AND CLINICAL IMPORTANCE

Computed tomography is an emerging imaging modality in cats with a suspected ureteral obstruction. Combination of CT and US can be beneficial for case management.

Survival and complications in cats treated with subcutaneous ureteral bypass

OBJECTIVES

To report the complications and factors affecting outcome for cats following placement of a subcutaneous ureteral bypass (SUB™).

MATERIALS AND METHODS

In this retrospective study, complications, the presence of a urinary tract infection and survival time were recorded following subctutaneous ureteral bypass placement. Factors affecting survival time were assessed using a Kaplan Meier curve and log rank test.

RESULTS

Ninety-five cats had 130 subcutaneous ureteral bypasses placed. Ten cats did not survive to discharge. Forty cats died or were euthanised after discharge (42%); the median survival time of these cats was 530 days (range 7 to 1915). Minor complications occurred in 18 cats (19%) and major complications occurred in 46 cats (48%), the majority of which were after hospital discharge. Twenty-seven cats were diagnosed with a urinary tract infection (UTI) post-operatively. A significant association between long-term survival and creatinine at presentation was identified. The median survival time for cats presenting with creatinine concentration ≥440 μmol/L (International Renal Interest Society stage acute kidney injury (AKI) 4 and 5) was 530 days (95% CI 273-787 days), compared to a median survival time of 949 days (95% CI 655-1243 days; Log Rank P=0.024) for those cats presenting with creatinine <440 μmol/L (International Renal Interest Society stage AKI 1-3).

CLINICAL SIGNIFICANCE

In this population of cats, subcutaneous ureteral bypass placement was associated with an approximately 10% in-hospital mortality and a high complication rate. Most complications were manageable, resulting in an overall median survival time of over 2 years.