Technical and clinical outcomes of ureteral stenting in cats with benign ureteral obstruction: 69 cases (2006�2010)

• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 244, Nº. 5, 2014, págs. 559-576
• Idioma: inglés
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• Resumen

  • Objective�To evaluate the technical, short-term, and long-term outcomes in cats with benign ureteral obstructions treated by means of double-pigtail ureteral stent placement.

    Design�Retrospective case series.

    Animals�69 cats (79 ureters).

    Procedures�The diagnosis of benign ureteral obstruction was made via abdominal ultrasonography, radiography, and ureteropyelography. Ureteral stent placement was attempted endoscopically, surgically, or both, with fluoroscopic guidance. The medical records were reviewed for pre-, intra-, and postoperative data; complications; and outcome.

    Results�69 cats (79 ureters) had stent placement attempted for various causes: ureterolithiasis (56/79 [71%]), stricture (10/79 [13%]), both ureterolithiasis and stricture (12/79 [15%]), or a purulent plug (1/79 [1%]). Stent placement was successful in 75 of 79 ureters (95%). Median number of stones per ureter was 4 (range, 0 to > 50), and 67 of 79 (85%) had concurrent nephrolithiasis. Preoperative azotemia was present in 95% (66/69) of cats (median creatinine concentration, 5.3 mg/dL [range, 1.1 to 25.8 mg/dL]), and 71% (49/69) remained azotemic (median, 2.1 mg/dL [range, 1.0 to 11.8 mg/dL]) after successful surgery. Procedure-related, postoperative (< 7 days), short-term (7 to 30 days), and long-term (> 30 days) complications occurred in 8.7% (6/69; 7/79 ureters), 9.1% (6/66), 9.8% (6/61), and 33% (20/60) of cats, respectively; most of these complications were minor and associated with intermittent dysuria or the need for ureteral stent exchange. The perioperative mortality rate was 7.5% (5/69), and no deaths were procedure related. The median survival time was 498 days (range, 2 to > 1,278 days). For patients with a renal cause of death, median survival time was > 1,262 days, with only 14 of 66 cats (21%) dying of chronic kidney disease. Nineteen (27%) cats needed a stent exchange (stricture in-growth [n = 10], migration [4], ureteritis [2], dysuria [2], pyelonephritis [1], or reflux [1]). No patient died of the procedure or recurrent ureteral obstruction.

    Conclusions and Clinical Relevance�Results of the present study indicated that ureteral stenting is an effective treatment for benign ureteral obstructions in cats regardless of obstructive location, cause, or stone number. The perioperative morbidity and mortality rates were lower than those reported with traditional ureteral surgery. The short- and long-term complications were typically minor but may necessitate stent exchange or use of an alternative device, particularly with ureteral strictures. The prognosis for feline ureteral obstructions after ureteral stenting could be considered good when the procedure is performed by trained specialists.

    Ureterolithiasis is the most common cause of ureteral obstruction in both canine and feline patients,1�5 although trigonal neoplasia,6,7 ureteral strictures (congenital or acquired),5,8,a�c and solidified blood clots and calculi9 have also been reported. The increasing incidence of ureteral obstructions in small animal patients, combined with the invasiveness and morbidity associated with traditional open surgical techniques,2,10 makes the use of newer interventional options appealing. Greater than 98% of ureteroliths in feline patients have been documented to be composed of calcium oxalate material.1,2,11 These types of stones will not dissolve with medical treatment and either need to pass spontaneously, be removed, or be bypassed to permit urine drainage and prevent renal damage. Once medical management fails, partial obstructions are often left untreated in many practices because of the risk-benefit ratio of attempted surgical removal.

    A study12 of normal dogs after a ureteral obstruction was created showed that renal blood flow diminishes to 40% of normal over the first 24 hours and to 20% of normal by 2 weeks. Furthermore, in another study of healthy dogs,13 the excessive back pressure was transmitted to the entire nephron, and a decrease in glomerular filtration rate occurred via concurrent vasoactive mediator release, leukocyte influx, and subsequent fibrosis. These and additional studies14�16 of experimental animals and human patients demonstrated that the longer the duration of ureteral obstruction, the more severe and irreversible the damage. In a study of dogs,13 after 7 days of obstruction, the glomerular filtration rate was permanently diminished by a mean of 35%, and when the obstruction lasted for 14 days, the glomerular filtration rate was diminished by 54%. These data were obtained from an experimental study13 in dogs with complete acute obstruction, without preexisting azotemia, chronic interstitial nephritis, or chronic obstruction. A worse outcome might be expected in patients that are azotemic and have exhausted their compensatory hypertrophy mechanisms prior to the obstruction. It was also shown13,15,16 to take > 4 months for residual renal function to return after an obstruction. Because many feline patients with ureteral obstructions have concurrent renal compromise1,2,4,5 and a history of chronic kidney disease, aggressive and early treatment is recommended to improve overall renal function and the likelihood of the best outcome.

    Studies2,17 suggest that surgical treatment is indicated when medical management fails. In 1 study of cats,2 there was an 8% documented and 13% presumptive stone passage rate, with a 33% mortality rate prior to discharge with medical management alone. This is compared with a 30% morbidity rate and 21% mortality rate after ureterotomy, ureteral reimplantation, ureteronephrectomy, or renal transplantation.2 The leading cause of perioperative complications was urinary leakage or ureteral re-obstruction due to a stricture at the surgical site, persistent ureteral calculi, or concurrent nephroliths that became ureterolith induced obstructions. Additionally, 40% of patients in that study2 had a ureteral obstruction recurrence, 86% of which had evidence of nephroliths at the time of the first surgery.2 Because of a high perioperative morbidity and mortality rate for feline patients undergoing medical or traditional surgical management for ureteral obstructions, other treatment modalities have been investigated.4,5,8,a�c In human patients, the development of and improvements in ureteroscopy, ureteral stenting, extracorporeal shockwave lithotripsy, laser lithotripsy, laparoscopy, and percutaneous nephroureterolithotomy have nearly eradicated the need for open ureteral surgery for stone disease, strictures, trauma, neoplasia, and congenital anomalies.18�27 Ureteroscopy, shockwave lithotripsy, and laparoscopic treatment of ureteral obstructions are not typically possible in feline patients because of the narrow diameter of the ureter in cats (0.3 to 0.4 mm).17,28,29 This anatomic limitation, and a report27 in human patients that ureteral stents cause passive ureteral dilation over a few days to weeks, have been the basis for investigation into ureteral stenting for the treatment of ureteral obstructions in feline patients.4,5,8,a,c Ureteral stenting was first introduced in 1967 for evaluation of human patients with malignant ureteral obstructions.23 Ureteral stents are still widely used to treat both benign and malignant obstructive disease in people, and this is now considered the standard of care in many clinical situations for either temporary or definitive treatment. The goals of ureteral stenting are to bypass a ureteral obstruction and stabilize concurrent azotemia, to allow passive ureteral dilation for improved urine flow, to manage edema following ureteroscopy or surgery, to improve the success of extracorporeal shockwave lithotripsy, and to aid in spontaneous stone passage.25,26 Ureteral stent placement in veterinary medicine was first reported in 2007 in canine and feline patients for the treatment of both benign and malignant disease.a Since that time, few reports4,5,8,c on their use in the management of canine and feline ureteral disease have been published. The objective of the study reported here was to describe the ureteral stenting procedure in feline patients in detail as well as the outcome for use of various ureteral stents for the treatment of a relatively large number of feline patients with naturally occurring benign ureteral obstructions.