Ectopic Ureters in Male Dogs: Review of 16 Clinical Cases (1999–2007)
Ureteral ectopia is a well-described cause of urinary incontinence in female dogs, but this condition has not been completely characterized in male dogs. Sixteen male dogs with ectopic ureters were evaluated between Jan 1999 and Mar 2007. Male dogs were similar to female dogs with ectopic ureters in terms of breed, presenting complaint, age of onset, and bilateral nature of the ectopia. Diagnosis was made by expert interpretation of imaging techniques such as excretory urography and contrast-enhanced computed tomography (CT). Overall, 11 of 13 dogs that had surgical correction of ectopic ureters were incontinent preoperatively. Urinary continence was restored in 82% of those dogs.
Introduction
Ureteral ectopia is a complex developmental abnormality of the urogenital system resulting from dysembryogenesis of the ureteral bud.1 It is the most common cause of either intermittent or continuous urinary incontinence in young female dogs.2 Ectopic ureters are defined by distal displacement of one or both ureteral orifices to a site distal to the expected anatomic position at the cranial border of the trigone.3 Two types of ectopic ureters are identified in female dogs based on anatomic pathway. Intramural ectopic ureters attach to the dorsolateral aspect of the bladder trigone, enter the bladder wall, but fail to open and drain into the lumen at this site. Instead, they extend distally from the trigone through a submucosal tunnel to open within the bladder neck, vesicourethral junction (VUJ), urethra, or vestibule.4 Extramural ectopic ureters exit the retroperitoneal space and fail to attach to any aspect of the bladder wall. Extramural ureters attach and open directly into the urethra, vagina, or vestibule.4 Intramural ectopic ureters are the most commonly reported type of ectopic ureter in both juvenile and adult female dogs, and the incidence of extramural ureters is considered rare.4–6 Ectopic ureters in dogs are documented with greater frequency in certain breeds of dogs including the Labrador retriever, golden retriever, Siberian husky, West Highland white terrier, wirehaired fox terrier, Newfoundland, poodle, and soft-coated wheaten terrier.6–9
In all species, including dogs, ectopic ureters are reported more commonly in females than in males.1,3 There is an overall 0.016% incidence of ectopic ureters in dogs, and affected female dogs are identified approximately 4–20 times more frequently than affected male dogs.2,7–11 It has been hypothesized that there may either be a true sexual predisposition for this anomaly or that ectopic ureters are underdiagnosed in male dogs due to lack of clinical signs of urinary incontinence.3 The longer length of the male urethra may oppose the distal flow of urine and prevent urine leakage.4,12 Alternatively, the increased pressure within the lumen of the prostatic urethra and external sphincter mechanism may oppose the passage of urine distally, resulting in retrograde bladder filling instead of incontinence.3
No complete characterization of ectopic ureters in male dogs has been published. Instead, there are single case reports and larger studies including, but not focusing on, male dogs. The purpose of this retrospective study was to provide a complete description of 16 male dogs with ectopic ureters, reporting the signalment, history, clinical presentation, clinicopathologic findings, method of diagnosis, surgical findings, treatment, and outcome. In addition, the authors compared the findings in the 16 included dogs to previous reports of male and female dogs in the veterinary literature.
Materials and Methods
Medical records of male dogs with a diagnosis of ectopic ureter between Jan 1999 and Mar 2007 at The Ohio State University Veterinary Teaching Hospital were reviewed. Dogs were identified by diagnostic classification in the computerized medical records and by a search of procedures in the surgery case logs. Dogs were included if the medical record contained a complete history, physical exam, results of laboratory findings and imaging studies, and a complete surgery report in cases when surgery had been performed.
Information summarized from the medical records included signalment (age, breed, sex, neuter status), presenting complaint, history, body weight and physical examination findings, laboratory findings (complete blood count [CBC], serum biochemical profile, urinalysis, results of aerobic bacteriologic culture of the urine), and the results of additional diagnostic procedures including contrast radiography, contrast-enhanced computed tomography (CT), abdominal ultrasonography, uroendoscopy, and determination of glomerular filtration rate (GFR) using nuclear scintigraphy. For patients that underwent surgical correction of ectopic ureters, the surgical report was summarized, including the description of anatomic findings and abnormalities, the specific location of each of the ureteral orifices, and the surgical procedures performed. Postoperative information included complications, length of hospital stay, and results of any postoperative laboratory work, urinalyses, or urine cultures. Follow-up phone calls to owners or referring veterinarians were made to assess case outcome, including characterization of urinary continence both before and after surgery based on a urinary incontinence scoring system (Table 1), complications associated with the surgical procedure, complications associated with the urogenital system, and owner satisfaction with their dog’s status.
Results
Sixteen male dogs diagnosed with ectopic ureters were included in this study. Of those, 15 of 16 (94%) dogs were diagnosed with bilateral ectopic ureters. One dog had a unilateral ectopic ureter affecting the right ureter. Ectopic ureteroceles (i.e., cystic dilatations of the submucosal portion of the distal ureter) were identified associated with the displaced ureters in four dogs, including the patient diagnosed with unilateral ectopic ureter.
Signalment
Affected breeds included nine Labrador retrievers (56%) and one each of the following: Shetland sheepdog, border terrier, rottweiler, West Highland white terrier, bichon frise, schipperke, and mixed-breed. The age at the onset of clinical signs, which led to referral for further diagnostics, ranged from 2 mo to 57 mo (median, 2 mo). Age at the time of diagnosis of ectopic ureters ranged from 3.5 mo to 66 mo (median, 15 mo). Body weight at the time of diagnosis ranged from 6.5 kg to 44 kg (mean, 23.2 kg; median, 21.6 kg). Seven of the affected male dogs (44%) were electively neutered before referral for symptoms of lower urinary tract disease. Six dogs (38%) were neutered at the time of surgical correction of ectopic ureters, including one dog that was bilaterally cryptorchid. One dog was neutered several months after surgical correction of ectopic ureters. One dog was neutered while under general anesthesia for advanced imaging procedures confirming the diagnosis of ectopic ureters, but corrective surgery was not performed. One dog was not neutered at the owner’s request.
Presentation
Overall, 13 of 16 (81%) male dogs with ectopic ureters presented for evaluation of urinary incontinence. Of those, 9 of 13 (69%) were puppies < 7 mo of age and 2 of 13 (15%) were young adults < 2 yr of age obtained from rescue organizations with no known history at the time of adoption. The remaining two dogs developed intermittent incontinence at approximately 5 yr of age (they were incontinent only when asleep or in a recumbent position).
No urinary incontinence occurred in 3 of 16 (19%) male dogs with ectopic ureters. Two of those dogs presented for evaluation of lower urinary tract disease and one presented for disorders unrelated to the urinary system (i.e., splenomegaly and a cardiac arrhythmia).
The frequency and severity of urinary incontinence at the time of presentation was variable. Clinical signs of urinary incontinence were scored for each patient using the urinary incontinence scoring system. The 16 male dogs with ectopic ureters were assigned the following continence scores based on owner history and clinical observations at the time of presentation: seven dogs (44%) were assigned a continence score of 1; two dogs (12%) received a continence score of 2; one dog (6%) received a continence score of 3; three dogs (19%) received continence score of 4; and three dogs (19%) with no signs of urinary incontinence were assigned a continence score of 5.
Overall, 11 of 13 (85%) dogs with urinary incontinence had been treated medically without resolution before referral. Four (31%) dogs had been treated with antibiotic therapy for either a suspected or confirmed urinary tract infection. The α-adrenergic agonist, phenylpropanolamine hydrochloride, was administered as the sole treatment of continuous urinary incontinence in two (15%) dogs. An additional four (31%) dogs were treated with an antimicrobial and phenylpropanolamine hydrochloride simultaneously. One dog (8%) received multiple trials of a variety of drugs, including antimicrobials, phenylpropanolamine hydrochloride, ephedrine sulfate, diphenhydramine, and testosterone cipionate in an attempt to control incontinence. Only two incontinent dogs (15%) received no medical treatment prior to referral.
Results of the physical examination were within normal limits for 10 of 16 (62%) dogs except for a variable amount of urine leakage during the examination indicated by their continence score. Additional physical examination abnormalities were identified in five dogs, including a palpable midabdominal mass suspected to be an enlarged kidney in three dogs, prostatomegaly in one dog, and bilateral cryptorchidism in one dog.
Diagnostics
A CBC and serum biochemistry were submitted for 15 of 16 (94%) affected dogs. No clinically relevant hematologic abnormalities were identified in any of those patients. A mild increase in the blood urea nitrogen concentration (21–31 mg/dL; reference range, 5–20 mg/dL) was present in three dogs. A concomitant mild increase in serum creatinine concentration (1.8 mg/dL; reference range, 0.6–1.6 mg/dL) was found in only one of those three dogs.
A urinalysis was performed as part of the diagnostic evaluation in 14 of 16 (88%) dogs. Urine samples were routinely collected by cystocentesis. Results of urinalyses were unremarkable except for isosthenuria (urine specific gravity 1.008–1.012) in one dog and hyposthenuria (urine specific gravity < 1.007) in one dog. Both of those dogs had normal CBCs and serum biochemistry profiles. Aerobic bacteriologic culture of urine collected via cystocentesis was performed at the time of presentation in all dogs. A positive bacterial culture was documented in only one dog. Pseudomonas spp. was isolated, but that dog had a history of two positive urine cultures before referral in which the bacterial isolate was E. coli spp. That patient had been treated previously with oral cephalexin and enrofloxacin.
Imaging
Imaging modalities such as excretory urography with and without fluoroscopy, retrograde urethrocystography, contrast-enhanced CT, abdominal ultrasonography, and uroendoscopy were variably used to confirm the diagnosis of ectopic ureters in the dogs included this study. All dogs had more than one form of imaging as part of their diagnostic evaluation.
Excretory urography
In total, 11 of 16 (69%) dogs in this study had excretory urography performed one or more times for a total of 16 procedures. Of those, three were performed at private specialty referral practices and 10 procedures were performed at The Ohio State University Veterinary Teaching Hospital and were evaluated by a single radiologist (V.S.). The remaining three excretory urograms were performed by local referring veterinarians and the results were sent with the patient at the time of referral.
A definitive diagnosis of ectopic ureter was made based on the findings from 11 of 16 (69%) excretory urograms. Unilateral right ectopic ureter with an ectopic ureterocele was diagnosed in one dog. The specific locations of the 21 ectopically displaced ureteral orifices identified by excretory urography included the distal trigone (one ureter), VUJ (eight ureters), and preprostatic urethra (12 ureters). Two ectopically displaced ureteral orifices were not identified based on results of excretory urography due to reduced renal function of the associated severely hydronephrotic kidney minimizing uptake of the contrast. The associated ectopic ureters never sufficiently contrast-enhanced due to their extreme dilation, resulting in further dilution of the contrast by urine pooling within the dilated, tortuous structure.
The five remaining excretory urograms were from local veterinary practices and were considered inconclusive for the diagnosis of ectopic ureters. Insufficient patient preparation was noted in two studies resulting in failure to visualize the course of the ureters due to fecal distention of the colon.
Additional associated abnormalities of the urogenital system identified from the excretory urograms included right hydronephrosis (two kidneys), left hydronephrosis (four kidneys), right ureteral dilatation (two ureters), left ureteral dilatation (four ureters), prostatomegaly (two prostates), dilation of right renal diverticulum (one kidney), and a small left kidney (one kidney).
Excretory urography was performed in 9 of 13 (69%) dogs that went to surgery. Excretory urography accurately predicted the location of 13 of 17 (76%) displaced ureteral orifices that were later verified at surgery.
Retrograde urethrocystography
Retrograde urethrocystography was performed in three dogs and lead to definitive diagnosis of ectopic ureters in one. Retrograde urethrocystography was not used as the sole imaging method in any dog in this study.
Contrast-enhanced CT
Contrast-enhanced CT was performed in 8 of 16 (50%) male dogs to evaluate structures of the urogenital system. All contrast-enhanced CT imaging was performed using the same protocol.13 Briefly, the bladder was emptied of urine and 60 mL of room air was infused into the bladder prior to removal of the urethral catheter. A series of 10 mm transverse and helically acquired images from the right kidney to the tuber ischium were obtained using a standard algorithm. Additional thin slice sections were obtained in the region of the trigone through the prostatic urethra to document ectopic status (Figure 1).
Citation: Journal of the American Animal Hospital Association 48, 6; 10.5326/JAAHA-MS-5302
Based on the results of contrast-enhanced CT alone, ectopic ureters were diagnosed in all eight dogs studied. The specific locations of 15 displaced ureteral orifices included the distal trigone (two orifices), VUJ (four orifices), preprostatic urethra (seven orifices), and prostatic urethra (two orifices). One ureter was judged to be ectopic, but the exact location of termination was not determined.
In addition to ectopic ureters, associated abnormalities of the urogenital tract identified from contrast-enhanced CT included right pyelectasia (one kidney), right hydroureter (three ureters), left hydronephrosis (four kidney), left hydroureter (six ureters), small left kidney (one kidney), abdominal testicles (two testicles), asymmetric prostate with cystic regions (one prostate), ectopic ureterocele (one ureter), and an amorphous mineralizing mass surrounding the proximal ureter without resultant dilatation (one ureter).
Contrast-enhanced CT was used in the evaluation of 6 of 13 (46.1%) dogs that went to surgery. Contrast-enhanced CT accurately identified the specific locations of 10 of 12 (83%) displaced ureteral orifices in those six dogs.
Ultrasound
Ultrasound examination of the abdomen was performed to evaluate the urogenital system in 9 of 16 (56%) male dogs. The definitive diagnosis of ectopic ureters could not be made in any of those dogs as ureteral jets in an ectopic location were not identified; however, identification of structural abnormalities of the upper or lower urinary system provided supportive information to assist in the preoperative assessment of patients with ectopic ureters. Additional abnormalities identified on ultrasound examination included right hydronephrosis (three kidneys), right hydroureter (three ureters), right pyelectasia (three kidneys), right ectopic ureterocele (two ureters), left hydronephrosis (three kidneys), left hydroureter (four ureters), left pyelectasia (two kidneys), small left kidney (one kidney), abdominal testicles (two testicles), prostatomegaly (one prostate), and a single band or tissue fold at the neck of one bladder.
Uroendoscopy
Endoscopic examination of the urethra and bladder was performed in 9 of 16 (56%) male dogs. A flexible ureteroscopea with an outer diameter of 2.7 mm was passed transurethrally in eight dogs to visualize the entire length of the urethra and luminal surface of the bladder. Uroendoscopy of the bladder and prostatic urethra was performed using a 2.7 mm rigid endoscopeb through a minimally invasive approach to the bladder in one dog that was too small to accommodate the flexible ureteroscope.
The recorded anatomic locations of the ureteral orifices in seven of the nine dogs visualized endoscopically were normal (one ureter), VUJ (one ureter), preprostatic urethra (eight ureters), and prostatic urethra (two ureters). It was not possible to visualize two ureters, and endoscopic examination of two dogs was inconclusive due to hemorrhage obscuring the visual field. Repeated attempts to clear the hemorrhage and control bleeding with cold fluid infusion were not successful.
Additional abnormalities of the lower urinary tract identified endoscopically included mucosal changes of the urethra (ranging from mild to severe urethritis) with areas of either focal hemorrhage or ulceration in three dogs.
Uroendoscopy was performed in 6 of 13 (46%) dogs that went to surgery. Direct visualization of the ureteral orifices using endoscopy accurately identified the location of 5 of 12 (41%) displaced ureters verified later at surgery.
GFR studies
Differential nuclear scintigraphy using technetium-99m diethylenetriaminepentaacetic acid was performed to determine GFR in 2 of 16 (13%) dogs, both with severe hydronephrosis. One dog diagnosed with severe unilateral left hydronephrosis and hydroureter had a total GFR of 3.71 mL/min/kg (reference range, 2.66–5.67 mL/min/kg).14 The GFR of the right kidney was determined to be 3.639 mL/min/kg and the GFR of the left kidney was 0.071 mL/min/kg. Nuclear scintigraphy was also performed on a second dog diagnosed with moderately severe, bilateral hydronephrosis and hydroureter based on excretory urography, contrast-enhanced CT, and ultrasonography. The total GFR was determined to be 2.578 mL/min/kg. GFR of the right kidney was 2.327 mL/min/kg and the GFR of the left kidney was 0.25 mL/min/kg.
Surgical Procedure
Surgical correction of 25 ectopic ureters was performed in 13 of 16 (81%) male dogs. Two of the 13 dogs that went to surgery had no signs of urinary incontinence and instead had lower urinary tract signs. The owners of the three dogs that did not go to surgery declined surgery for various reasons, including the following: financial concerns, pet had no signs of incontinence (continence score of 5), or the owner could tolerate occasional incontinence (continence score of 4).
Specific surgical correction was based on the location of the ureteral orifice and the associated abnormalities of the urinary system. A ventral midline celiotomy extending to the pubis was performed on all dogs to expose the upper and lower urinary system, permitting examination of each kidney and ureter. Ventral midline cystotomy and urethrotomy were performed to identify the specific anatomic termination of each ureteral orifice. Appropriately sized red rubber urethral catheters (3.5–8 French)c were used to catheterize each of the ureteral orifices, aiding in visualization of the submucosal aspect of the distal ureter. Ureteral transposition was performed if the site where the ureter entered the bladder wall was distal to the cranial border of the trigone. Neoureterostomy was elected if the site where the ureter entered the bladder was appropriately positioned, but the opening was distal to the cranial border of the trigone. The distal submucosal ureteral remnants were excised from surrounding tissues as they passed through the trigone, preprostatic, or prostatic urethra (where indicated) with reconstruction of the resulting defects in all 13 dogs.
Surgical procedures performed on the 25 ectopic ureters included ureteral transposition of displaced ureters (n = 8), neoureterostomy of displaced ureters (n = 13), and unilateral ureteronephrectomy of displaced ureters (n = 4). Ureteronephrectomy was elected based on poor renal function in the affected kidney as determined by preoperative GFR using nuclear scintigraphy (n = 2) or excretory urography (n = 2). The left kidney was removed in all four dogs.
Surgical Findings
Overall, 12 of 13 (92%) dogs that went to surgery had bilateral ectopic ureters. All were intramural ectopic ureters with submucosal tunnels of varying length. As illustrated in Figure 2, the specific sites of the displaced ureteral orifices included six located distal to the cranial border of the trigone (24%), eight in the VUJ (32%), nine in the preprostatic urethra (36%), and two within the prostatic urethra (8%). Ectopic ureteroceles were identified in 3 of 13 (23%) dogs at surgery. Two of those dogs required ureteronephrectomy because of ureteral dilation and hydronephrosis.
Citation: Journal of the American Animal Hospital Association 48, 6; 10.5326/JAAHA-MS-5302
Postoperative Complications
All dogs were hospitalized postsurgically. The average length of hospitalization was 3.7 days (range, 2–5 days). Overall, 11 of 13 dogs had a balloon-tipped urethral catheter attached to a closed urine collection system placed after surgery. The average length of time the urinary catheters were maintained was 1.7 days postsurgically (range, 1–3 days). Urethral obstruction did not occur in any patient after catheter removal.
Seven dogs had aerobic bacteriologic cultures of urine samples obtained via cystocentesis submitted before discharge from the hospital, including the dog with a Pseudomonas spp. urinary tract infection diagnosed preoperatively. Only one urine sample was positive and grew Staphylococcus spp. postoperatively. Antibiotic therapy indicated by sensitivity results was continued for 21 days after surgery. No urine culture was performed on this dog preoperatively, so it is unknown whether this was a persistent or new infection.
No postoperative complications resulting in additional surgery, extended hospitalization, death, or euthanasia occurred in any male dog after surgical correction of ectopic ureters.
Outcome
Overall, 12 of 13 owners were available for a follow-up telephone interview. The average length of time between surgery and follow-up was 28 ± 6.5 mo (range, 1–62 mo). Of the 12 owners that were contacted, 11 (92%) were satisfied with the results of surgery. An excellent outcome was noted in 9 of 11 of those dogs (continence score was 5). Clinical signs of urinary incontinence initially improved in both of the two remaining dogs. One of those two dogs improved and was assigned a continence score of 5 initially, but approximately 8 wk after surgery, that dog experienced urine leakage associated with exercise. Daily medical therapy with oxybutynin (0.2 mg/kg per os q 12 hr) was instituted, which improved clinical signs so intermittent urine leakage was only noted once q 7 days at the most. The owners were satisfied with the results of surgery even though oral medication was required. That dog had bilateral ectopic ureters at the distal trigone and had bilateral neoureterostomy and trigonal/urethral reconstruction. The second dog’s clinical continence score changed from 1 presurgically to only 2 postsurgically. Phenylpropanolamine therapy was attempted with no improvement. Reevaluation 12 mo after surgery demonstrated no evidence of urinary tract infection based on results of urine culture obtained by cystocentesis. This is the only dog considered to have an unsatisfactory surgical outcome. Ectopic ureter terminations were at the VUJ and preprostatic urethra. Neoureterostomy and ureteronephrectomy, including removal of an ureterocele, were performed at surgery.
Five dogs had follow-up serum biochemistry profiles provided by the referring veterinarian 1–5 yr after surgery. None of those dogs were azotemic before surgery or at follow-up. Four dogs had aerobic bacteriologic cultures of urine collected by cystocentesis between 2 wk and 10 wk after surgery, including the dog with the Staphylococcus spp. infection. No bacterial growth was identified from any urine sample.
Discussion
Between 1968 and 2006, there were a total of 12 reports in the veterinary literature describing 35 male dogs with ectopic ureters. Those reports were either single case studies (n = 6) or as part of a larger retrospective review (n = 29).4,6,7,12,15–22 The breed of male dog was designated in many, but not all, of the previously published studies. Those breeds included Labrador retrievers (9 of 35, 26%), golden retrievers (6 of 35, 17%), Siberian huskies (3 of 35, 9%), and mixed-breeds (5 of 35, 14%). A breed predisposition for Labrador retrievers (56%) was also identified in this current report of male dogs with ectopic ureters. It has been suggested that a genetic basis exists for ectopic ureters, and its prevalence in the Labrador retriever and golden retriever populations supports this. To date, no controlled breeding studies, pedigree analysis, or DNA evaluation for gene mutations have been performed.10
A clinical history, including the reason for referral or presentation, was available for 27 of 35 male dogs with ectopic ureters reported in the literature.4,6,7,12,15–17,19,22 Of those, 25 (93%) presented for urinary incontinence, and the median age at diagnosis was 2.4 yr.4,6,7,12,16,17,22 The age at onset of incontinence was stated for only two of those dogs, which was 5 wk and 2.5 yr.15,19 Thirteen of the dogs in the current study presented for urinary incontinence, and the median age at onset was 2 mo and the median age at diagnosis was 15 mo. The current study supports the finding appreciated after reviewing the previously published studies that most male dogs with ectopic ureters present with urinary incontinence. The group of male dogs included in the current study, however, was younger at both age of onset and diagnosis. The reason for this discrepancy may represent a change in disease characteristics. Alternatively, the discrepancy in age of onset could also be explained by a lack of reporting in previous publications because the literature states the age at onset for only two dogs.
It is impossible to determine the frequency and severity of the incontinence in affected dogs previously reported due to incomplete characterization. In the current study, more than two-thirds of the incontinent dogs were severely affected (continence scores were 1 or 2), indicating incontinence > 50% of the time when sleeping or awake. Ectopic ureters were confirmed by surgery in two dogs without urinary incontinence, suggesting there are nonsymptomatic male dogs that remain undiagnosed. These undiagnosed affected male dogs may contribute to the perpetuation of this anomaly when used in breeding programs if ectopic ureters are genetic.
Of the 35 previously reported male dogs, 16 had ectopic ureters that were specified as either bilateral (56%) or unilateral (44%).7,12,15–17,19–22 Of the 13 dogs that had ureteral terminations verified at surgery in the current study, 12 had bilateral ectopic ureters (92%). Although it is possible that changing disease characteristics may have contributed to the increased number of dogs currently identified with bilateral ectopic ureters, it is more likely that advances in anatomic knowledge of this anomaly and improved diagnostic imaging have played a role in identifying displaced ureters at surgery that were previously missed.
Location of ureteral termination in the group of dogs included in the current study differed from previous reports; however, it should be noted that the specific locations were not included in most of the published reports. Holt and Moore (1995) reported 19 male dogs that all had ectopic ureters terminating in the prostatic urethra.4 In addition, three male dogs were described with ureteral terminations at the preprostatic urethra (n = 1) and prostatic urethra (n = 2).15,20,22 The specific locations of the ureteral orifices in the male dogs in the current study were determined by diagnostic imaging and subsequently verified at surgery in 81% of the included dogs. Direct visualization at surgery verified the prostatic urethra was the termination site in only 8% of the displaced ureteral orifices, making it the least common site of ureteral termination. The remaining 23 displaced ureteral orifices were distributed fairly evenly among the distal trigone (24%), VUJ (32%), and preprostatic urethra (36%). This difference in ureteral termination location is most likely related to the technical advances and type of preoperative imaging modalities that are currently available to guide the surgical explore. Excretory urography and urethrocystography were the only imaging modalities used in the preoperative assessment of previously reported male dogs with ectopic ureters.4,6,7,12,15–22 Both of those imaging modalities can obscure the ureteral orifice by the presence of contrast in the urethra or superimposition of pelvic structures, leading to concluding the ureteral termination is further distal than in it truly is.
One recent report has shown the diagnostic utility of contrast-enhanced CT in female and male dogs with ectopic ureters.13 The improved spatial and temporal resolution of helically or axially acquired transverse imaging through CT allows a more detailed evaluation of lower urinary tract anatomy because the view is not obscured by overlying structures.13 Thin slice sections through the trigone and distal urinary tract are necessary to document the ectopic status.13 Contrast-enhanced CT correctly identified the specific location of ureteral termination in > 80% of the dogs included in the current study that had contrast-enhanced CT and subsequent surgery for verification. This study supports the use of contrast-enhanced CT as a main imaging technique to guide surgical exploration and repair of ectopic ureters in male dogs.
The value of uroendoscopy could have been construed as equal or even better than contrast-enhanced CT based on a recent study in which all displaced ureteral orifices in 24 female dogs that were correctly diagnosed using a rigid cystoscope.5 Instead, in this study of male dogs, transurethral uroendoscopy using a 2.7 mm flexible ureteroscope accurately predicted the specific locations of < 50% of the displaced ureters. Endoscopic imaging of the urogenital system permits direct visualization of the luminal surface of the urethra and bladder under magnification through an optically clear fluid.3,5,10 Rigid endoscopy used in female dogs provides superior imaging compared with the same size flexible endoscope used in male dogs based on image clarity and the amount of illumination of the visual field, perhaps accounting for part of the discrepancy in diagnostic utility between uroendoscopy in females and in the group of male dogs included in the current study.3,5,10 Additionally, operators are far more experienced in evaluating female lower urinary tract anatomy compared with males. In males, there are many small openings located along the dorsal aspect of the prostatic urethra, including the seminal colliculus, deferent ducts, and numerous prostatic ducts, making it difficult to decipher normal anatomic structures from a displaced ureteral orifice.23 Further, magnification, although helpful, can distort measurements when attempting to determine the specific location.
Findings of concurrent urinary tract abnormalities such as ureteral dilatation and hydronephrosis were consistent with what has been previously reported in both male and female dogs with ectopic ureters.3,4,6,7,12,15–22 Ureteral dilatation is the most commonly identified abnormality secondary to ureteral displacement, and ureteral dilations were evident in 45.1% of the ectopic ureters in male dogs in this study.6,9,24 Ureteral dilatation is typically associated with intramural ureters that are displaced into the urethra. Changes in intraluminal urethral pressure can result in either partial or intermittent obstruction of urine flow through the displaced ureter by compression or collapse of the submucosal tunnel.10 Hydroureter, pyelectasia, and hydronephrosis can occur either due to sustained increased intrapelvic pressures or secondary to bacterial infection. In this study, hydronephrosis was identified in 25.8% of the kidneys associated with ureteral displacement, but only one positive bacteriologic urine culture identified at presentation. Based on the results of the two excretory urography studies and two nuclear scintigraphy studies, renal function was significantly compromised in four kidneys with severe hydronephrosis. Ureteronephrectomy was performed and microscopic evaluation of these kidneys revealed severe cortical and medullary compression and atrophy with areas of either mild neutrophilic or lymphocytic inflammation. Evidence of segmental zones of immature glomeruli within the atrophic cortex was identified in one of the four kidneys. Immature mesenchymal tissue was associated with those regions, suggesting concurrent renal dysplasia. The etiology of hydronephrosis was not determined histopathologically in any of the samples submitted.
Ureteroceles have been reported infrequently in the veterinary literature, with only one report of a male dog with an ectopic ureterocele.22,25–28 Four ectopic ureteroceles were identified in male dogs included in the current study. Three were verified at surgery and one was seen on ultrasound in a dog that did not have surgery performed. The prevalence of ureteroceles identified in this group of 16 male dogs with ectopic ureters supports an association between the dysembryogenesis of the ureteral bud resulting in the development of ectopic ureters and the formation of ureteral ectasia or ureteroceles in male dogs.
In this study, surgical correction of ectopic ureters resulted in urinary continence in 82% of the male dogs that were previously incontinent. This rate of surgical success is higher than the 44–67% previously reported for female dogs.2,4,6,7,21,29 In previous reports of male dogs that include surgical outcomes, a surgical success rate of 75% was achieved (based on one surgery leading to resolution of clinical signs in 6 of 8 male dogs with preoperative incontinence).6,7,12,16,18–20,22 It is possible that the improved postoperative continence in male dogs with ectopic ureters is due to less frequent concomitant urethral sphincter mechanism incompetence than female dogs with ectopic ureters. The authors believe that the most significant contributor to the surgical success rate noted in the current study is reconstruction of the bladder neck and proximal urethra after complete excision of tunneling terminal ureteral segments. This restores the anatomy of the bladder neck and proximal urethra and may improve function of the high-pressure zone or sphincter mechanism. Further study, including urethral pressure profilometry, is required to prove this hypothesis.
Conclusion
It has long been understood that male dogs are less frequently diagnosed with ectopic ureters than female dogs; however, until now, a complete evaluation of affected male dogs has not been described in the veterinary literature. This study comprehensively characterized male dogs with ectopic ureters that presented most often for severe, juvenile, urinary incontinence and were bilaterally affected. Labrador retrievers comprised over half of the male dogs diagnosed with ectopic ureters in this group. No other breed had more than one representative. Contrast-enhanced CT and excretory urography were reliable methods of diagnosis when expertly interpreted. Unlike previous descriptions, the prostatic urethra was not the most common site of ureteral termination. It was, in fact, the least common. Instead, there was a fairly even distribution of ureteral terminations at the distal trigone, VUJ, and proximal urethra. These findings show that a high number of male dogs with ectopic ureters have additional abnormalities such as hydronephrosis, hydroureter, and ureterocele. This may suggest that a closer look for ectopic ureters in male dogs is indicated when such abnormalities are noted. Surgical repair of ectopic ureters in male dogs can be more successful than previously described in female dogs because of less frequent concomitant urethral sphincter mechanism incompetence in male dogs. Additional studies are needed to prove the value of reconstruction of the proximal urethra and trigone when performed with ureteronephrectomy, ureteral transposition, or neoureterostomy for repair of ectopic ureters in male dogs.
Postcontrast, 3 mm, transverse contiguous computed tomography (CT) image at the level of the body of the seventh vertebral body of a 5 yr old male Labrador retriever. The prepuce (Pr) is appreciated ventrally with the central opacity of the os penis. The colon (Co), containing mineral material and gas, is dorsal to the contrast-enhanced ureters, which are identified with white arrows. Both ureters are dilated and continue past the caudal aspect of the urinary bladder (UB). Note the tortuous nature of the left ectopic ureter. A CT diagnosis was made of bilateral intravesicular ectopic ureters, both terminating at the proximal urethra (not shown in this image). L7, seventh lumbar vertebra; R, right.
Schematic drawing of the trigone area of the urinary bladder, bladder neck, urethra, prostate, normal ureteral opening, ectopic ureteral pathways (white tubular structures), and the locations of the 25 ectopic ureteral openings verified by surgery (dark gray circles). Ureteroceles are identified with an asterisk (*). L, left; R, right.
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