Extramural Ectopic Ureter in a Domestic Ferret (Mustela putorius furo)

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Extramural Ectopic Ureter in a Domestic Ferret (Mustela putorius furo) Theresa A. MacNab, DVM, Brent T. Newcomb, DVM, Cornelia Ketz-Riley, DVM, Robert D. Pechman, DVM, Dip. ACVR, and Mark C. Rochat, DVM, MS, Dip. ACVS

Abstract Ectopic ureter is the most common cause of congenital urinary incontinence in the dog and cat. The occurrence of ectopic ureter in the dog has been estimated to be 0.016%. A 6-month-old ferret was evaluated for urinary incontinence and urine scalding around the perineal and inguinal areas. Ultrasonography showed a nondistended urinary bladder that contained a possible intraluminal blood clot. Excretory urography revealed a left ectopic ureter. The ferret was initially treated with oral amoxicillinclavulanate and topical silver sulfadiazine ointment for the perineal and inguinal dermatitis associated with the incontinence. Because of the potential for complications and additional surgery with ureteral transplantation, a left nephroureterectomy was performed. Surgical recovery was uneventful and the incontinence improved, although a small amount of incontinence-associated dermatitis was still present 24 days after discharge. Phenylpropanolamine therapy was initiated to address a suspected dysfunction of the urethral sphincter. Urinary incontinence improved with the phenylpropanolamine therapy; however, a small amount of incontinence persisted throughout the 3 months in which the ferret was evaluated. To the authors’ knowledge, this is the first report of an ectopic ureter in a domestic ferret. © 2010 Published by Elsevier Inc. Key words: ectopic ureter; extramural; ferret; Mustela putorius furo; surgery

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6-month-old spayed female domestic ferret (Mustela putorius furo) weighing 914 g was referred to the Oklahoma State University Boren Veterinary Medical Teaching Hospital for evaluation of urinary incontinence. A urinalysis performed by the referring veterinarian the week before presentation revealed no abnormalities, and a urinary culture was not performed at that time. On physical examination of the ferret, urine scalding was observed around the genitalia, inguinal area, and caudal ventral abdomen. The ferret appeared painful on palpation of the caudal abdomen. The results of a complete blood count and serum biochemistry profile were within normal limits. An ab-

dominal ultrasonogram revealed several enlarged mesenteric lymph nodes and a small bladder with an intraluminal mass. Because of deformability and ab-

From the Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK USA. Address correspondence to: Theresa A. MacNab, DVM, Department of Veterinary Clinical Sciences, Center for Veterinary Health Sciences, Oklahoma State University, 1 BVMTH, Stillwater, OK 74078-2041. E-mail: [email protected]. © 2010 Published by Elsevier Inc. 1557-5063/10/1904-$30.00 doi:10.1053/j.jepm.2010.10.012

Journal of Exotic Pet Medicine, Vol 19, No 4 (October), 2010: pp 313–316

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Figure 1. Right oblique view of the excretory urogram 10 minutes postcontrast administration. Note the accumulation of contrast material within the renal pelvis (K), excretion of contrast material via the ureter (U), a lack of urinary bladder filling, and urethral location of the ectopic ureter (E).

sence of attachment to the bladder wall, the mass was believed to be consistent with a blood clot. Ultrasonography was unable to confirm the presence or absence of an ectopic ureter. Although attempted, urine could not be collected for a recheck urinalysis. An excretory urogram was performed with the ferret under general anesthesia. Iohexol (Omnipaque 240; Amersham Health, Princeton, NJ USA) was administered at 880 mg/kg. Ventrodorsal, lateral, right, and left oblique views were obtained at 1, 10, 20, and 45 minutes postinjection of the contrast agent. The contrast study revealed a left ureter that extended well beyond the normal entrance into the urinary bladder and progressed to enter either the distal urethra or vagina (Fig 1). The findings of the excretory urogram were consistent with the diagnosis of a left extramural ectopic ureter. The right ureter appeared to enter normally into the trigone area of the bladder. Both ureteral diameters were less than 1 mm and were considered to be within normal size for the patient. The kidneys appeared to have normal morphology on all images. Amoxicillin/clavulanate (20 mg/kg, by mouth every 12 hours, Clavamox; Pfizer, New York, NY USA) and topical silver sulfadiazine (SSD cream; Watson

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Laboratories Inc., Corona, CA USA) were prescribed before surgery to address the dermal infection and suspected urinary tract infection. Amoxicillin/clavulanate was selected because of the broad spectrum of antimicrobial activity required to treat the dermal and suspected urinary tract infections, as well as the ease of administering a palatable liquid formulation. Surgery to address the ectopic ureter was postponed for 2 weeks to allow healing of the affected skin. When the ferret presented for surgery, the caudal ventral abdominal dermatitis had almost completely healed and the patient appeared less painful on abdominal palpation. The owner was unwilling to risk the need for a second surgical procedure should an ureteroneocystostomy fail; therefore, a left-sided nephroureterectomy was performed. Buprenorphine (10 ␮g/kg intramuscularly, Buprenex; Reckitt and Colman Pharmaceuticals, Richmond, VA USA) was administered for premedication before induction. Anesthesia was induced for tracheal intubation with isoflurane (IsoFlo; Abbott Labs, North Chicago, IL USA) through the use of an induction chamber. The ferret was intubated with a 2-mm uncuffed endotracheal tube. Anesthesia was maintained with 2% isoflurane and 1.5-L oxygen by precision vaporizer and a nonrebreathing circuit. A fentanyl constantrate infusion (10 ␮g/kg/h intravenously, Sublimaze; Taylor Pharmaceuticals, Decatur, IL USA) was administered throughout surgery for analgesia. A ventral midline laparotomy was performed and the left ureter was observed to cross dorsal to the bladder and enter the genitourinary tract at some point caudal to the brim of the pubis. The left kidney was dissected from the perirenal fossa and the renal vessels ligated at the renal pedicle. Next, the left ureter was ligated as far distal as could be visualized, just caudal to the pubic brim. Both ligatures were circumferential and placed with 3-0 polydioxanone suture (PDS II; Ethicon Inc., Somerville, NJ USA). The bladder was within normal limits via external palpation. The abdominal wall and subcutaneous tissue were each closed with a simple continuous pattern of 3-0 polydioxanone. The skin incision was closed with a continuous pattern of poliglecaprone (Monocryl; Ethicon Inc.). Recovery from anesthesia was uneventful. The amoxicillin-clavulanate and SSD cream were continued as described for 14 days, and meloxicam (0.2 mg/kg, by mouth every 24 hours for 5 days, Metacam; Boehringer Ingelheim, St. Joseph, MO USA) was added to the treatment protocol to provide analgesic and antiinflammatory effects. Ten days after surgery the primary dermatitis had resolved and the surgical incision was healed. Some urinary incontinence was still noted by the owner;

Extramural Ectopic Ureter in a Ferret

however, much less urine appeared to be present in the inguinal area and the ferret had been observed purposefully urinating. No abnormalities in kidney function were noted on a recheck serum chemistry panel. The ferret did develop a small area of perivulvar dermatitis, which was suspected to be associated with self-trauma secondary to licking the SSD cream. Because of this, the SSD cream was discontinued and the amoxicillin-clavulanate continued for another 7 days. Ideally, a urine culture would have been performed postoperatively; however, the patient was fractious at the recheck appointments and the owners declined sedation for a cystocentesis. Twenty-four days after the surgical procedure the ferret still had the perivulvar dermatitis and the owners reported some continued urinary incontinence. Phenylpropanolamine (2.2 mg/kg by mouth every 8 hours, Proin drops; PRN Pharmaceuticals, Pensacola, FL USA) was initiated to address suspected dysfunction of the urethral sphincter. Administration of phenylpropanolamine did decrease the incontinence and the ferret began purposefully using the litter box; however, a minimal amount of incontinence and some urine scald–associated dermatitis persisted through the recheck examinations. Follow-up abdominal ultrasonography or contrast cystography to determine the degree of urinary bladder distension and wall thickness was declined by the owner.

Discussion There are no reports of ectopic ureters in the domestic ferret. Reported urinary tract disorders that potentially cause incontinence in this species include urolithiasis, bacterial cystitis, and renal cysts.1 The disease conditions listed above commonly cause clinical signs that include pollakiuria and stranguria. Depending on the severity of these clinical signs, urine scalding may also develop in the inguinal region of the affected patient. On presentation, urine scalding was the most obvious clinical sign affecting the ferret described in this report. The number of more common conditions that result in urine scalding emphasizes the need to rule out diseases such as urinary calculi and cystitis before pursuing a diagnosis of ectopic ureter. Ectopic ureter is a developmental anomaly in which one or both ureters terminate at a location other than the trigone of the bladder. Urinary incontinence occurs when the abnormal termination of the ureter is caudal to the urethral sphincter. Clinical signs that may be observed in animals that have an ectopic ureter(s) include intermittent or persistent urinary incontinence, urine scalding, and

315 a history of episodic urinary tract infections. An ectopic ureter that terminates cranial to the urethral sphincter may result in no overt clinical signs.2-5 Ectopic ureters can occur intramurally or extramurally. The most common type of ectopic ureter diagnosed in dogs is intramural, where the ureter enters the urinary bladder wall dorsally near the trigone and then courses submucosally to open into the urethra in a more distal location.2 In cats, extramural ectopic ureters are commonly diagnosed and enter the urinary tract caudal to the trigone.4,6 The ectopic ureter in the ferret of this report extended extramurally, entering either the distal urethra or vagina. Ectopic ureters are the most common cause of congenital urinary incontinence in dogs and cats.5,7 In dogs, the occurrence of ectopic ureters has been estimated to be 0.016%.5 Some breed predilections have been proposed in the dog, and it has been suggested that a genetic relationship may exist in other animals too.3 Ureteral ectopia is diagnosed 20 times more often in female than male dogs, with a more even distribution between male and female cats.2 It has been hypothesized that the increased frequency of diagnosis in the female dog may be due to the anatomic differences from male dogs. The longer urethral length of a male dog allows termination of an ectopic ureter in the urethra, with enough residual urethral length to maintain continence.1,5 Ectopic ureter reports are rare in the cat.4 In domestic ferrets the only congenital anomalies of the urogenital tract that have been reported are renal and ureteral cysts.8 Because there are no other reports of ureteral ectopia in domestic ferrets and the genetic background of the ferret in this report is unknown, it is not possible to comment with confidence on the heritability of ureteral ectopia in ferrets; however, the fact that many ferrets available in the US pet trade originate from one of only a few breeding lines suggests that this disease is not likely to have a strong heritable component. Diagnostic testing used in obtaining a definitive diagnosis of ectopic ureters include survey radiography, ultrasonography, excretory urography, urethrocystography, pneumocystography, computed tomography (CT), contrast-enhanced CT, and urethral pressure profilometry.6 The diagnosis of ectopic ureters can also be achieved with transurethral cystoscopy in patients that have urethras of sufficient size.2,5 Cystoscopy has been performed with a 1-mm flexible endoscope in male cats.9 However, in this case, the smaller size of the ferret urethra precluded transurethral cystoscopy, ultrasonography was unable to confirm or rule out the presence of an ectopic

316 ureter, and the definitive diagnosis was ultimately made with excretory urography. A CT evaluation would have been ideal to further elucidate the location and nature of the ectopic ureters; however, because of financial constraints and the quality of information gained from the excretory urogram, the diagnosis was considered sufficient to proceed to the treatment options. The definitive treatment for an ectopic ureter is surgery. Approaches such as transurethral cystoscopicguided laser ablation to treat intramural ureteral ectopia have been performed in the dog and have proven to be effective.10 The most common procedure used for extramural ectopic ureters is ureteral reimplantation.3 A nephroureterectomy was performed in this case because there was concern that the small luminal diameter of the ureter may have increased the risk of postoperative ureteral stricture, and the owner was unwilling to pursue a second surgery should ureteral stricture occur and hydronephrosis develop. Postoperatively, 44% to 67% of dogs treated for ectopic ureters have some degree of urinary incontinence.2 Postoperative urinary incontinence has been found to be associated with concurrent dysfunction of the urethral sphincter, a hypoplastic urinary bladder, other related congenital abnormalities, or bacterial cystitis. In many of these cases, the postoperative incontinence remains idiopathic.1-3 The ferret of this report continued to have a small degree of urinary incontinence with much improvement observed after instituting oral phenylpropanolamine. Dosages for the phenylpropanolamine were extrapolated from published doses for the domestic cat. Consequently, the lack of complete remission may reflect an inability to achieve a therapeutic dose of this drug in the ferret. Other abnormalities in this ferret’s urinary tract, such as a hypoplastic bladder, may have also been present and contributed to the continued incontinence. This article serves to establish that ectopic ureter can occur in ferrets, and this species appears to share similar clinical features of ectopic ureters reported in cats. The authors recommend that ectopic ureters

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should be considered as a differential diagnosis whenever common lower urinary tract disease signs associated with urinary incontinence fail to respond or resolve with appropriate therapy. The diagnostic approach and treatment for ectopic ureters in ferrets are similar to those used for dogs and cats.

Acknowledgments The authors would like to thank John Hoover, DVM, MS, Dip. ABVP, Dip. ACVIM, for his help editing this manuscript, and Jill Murray, RVT, for going above and beyond in the management of this case.

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