Ectopic Ureter

Ectopic ureter is a congenital malformation in which one or both ureters fail to terminate at the normal location in the trigone of the urinary bladder, instead inserting into the urethra, vagina, vestibule, or, rarely, other pelvic structures. This aberrant insertion bypasses the urinary continence mechanism, leading to continuous or intermittent urinary incontinence, often from birth or weaning. The condition is classified as intramural or extramural based on the path of the ureter relative to the bladder wall. Intramural ectopic ureters course through the bladder wall submucosally before opening ectopically, while extramural ureters bypass the bladder entirely. The anomaly may be unilateral or bilateral, and can be associated with other urogenital malformations such as ureteroceles, renal dysplasia, and bladder hypoplasia. Surgical correction aims to reimplant the ureter into the bladder at the normal trigonal position, restoring urinary continence and preserving renal function.

The exact etiology of ectopic ureter is not fully understood, but it is considered a congenital developmental anomaly resulting from abnormal differentiation of the ureteral bud and its interaction with the metanephric blastema. During embryogenesis, the ureteral bud arises from the mesonephric duct and migrates to the trigone. Failure of this migration or abnormal absorption of the ureteral orifice into the bladder leads to ectopic termination. Genetic factors are implicated, with a hereditary basis suspected in certain breeds, particularly Siberian Huskies and Golden Retrievers. No traumatic, infectious, or neoplastic causes have been identified. The condition is present at birth, although clinical signs may not be recognized until after weaning. Associated anomalies, such as ureterocele, renal dysplasia, and vaginal strictures, may share a common embryological origin, suggesting a field defect in urogenital development.

Ectopic ureter is the most common cause of urinary incontinence in young female dogs, with a reported incidence of 0.05% in the general canine population. It is significantly more common in females than males, with a female-to-male ratio of approximately 20:1. In males, the condition is rare and often associated with other severe urogenital anomalies. Certain breeds are overrepresented, including Siberian Huskies, Golden Retrievers, Labrador Retrievers, Newfoundlands, Poodles, and West Highland White Terriers. In cats, the condition is less common but has been reported in both domestic shorthair and purebred cats. The age at presentation is typically less than 1 year, with many animals showing signs of incontinence from birth or at the time of weaning. There is no known sex predilection in cats. The condition is often diagnosed in young animals, but delayed diagnosis can occur in cases with mild incontinence or in animals with good urethral sphincter tone.

The pathophysiology of ectopic ureter involves the abnormal insertion of the ureter into the urethra or genital tract, bypassing the normal urinary continence mechanism. The ureter normally enters the bladder at the trigone, where the ureteral orifice is surrounded by the ureteral tunnel and the trigonal musculature, which contribute to the antireflux mechanism and urinary continence. In ectopic ureter, the ureter may enter the urethra, where it is subject to the high pressures of the urethral sphincter, but the lack of a submucosal tunnel and the abnormal location prevent the normal flap-valve effect, leading to reflux and incontinence. Additionally, the ectopic ureter may be associated with a hypoplastic bladder, which reduces bladder capacity and compliance, exacerbating incontinence. The continuous leakage of urine can lead to urine scald dermatitis and ascending urinary tract infections. In cases of bilateral ectopic ureters, renal function may be compromised due to associated renal dysplasia or hydronephrosis from ureteral obstruction or reflux. The abnormal embryological development may also affect the development of the urethral sphincter, leading to intrinsic sphincter mechanism incompetence, which can persist even after surgical correction.

Predisposing factors for ectopic ureter are primarily genetic and breed-related. A hereditary basis is suspected in certain breeds, with a polygenic mode of inheritance proposed. In Siberian Huskies, a familial pattern has been observed, suggesting a genetic predisposition. Other intrinsic factors include female sex, as the condition is much more common in females, likely due to the shorter urethra and the anatomical proximity of the ureteral orifices to the genital tract. Congenital anomalies such as ureterocele, renal dysplasia, and bladder hypoplasia are often concurrent and may predispose to the development of ectopic ureter. Extrinsic factors are not known to play a role, as the condition is congenital. However, early spaying or neutering may unmask the condition due to the influence of sex hormones on urethral sphincter tone, but this is not a causative factor. Obesity and urinary tract infections may exacerbate clinical signs but do not predispose to the anomaly.

The most common clinical sign of ectopic ureter is continuous or intermittent urinary incontinence, typically present from birth or weaning. Affected animals may dribble urine, especially when recumbent or excited, and may have a wet perineum. In females, urine may be observed pooling in the vaginal vestibule. In males, incontinence may be less obvious due to the longer urethra, but urine may be seen dripping from the prepuce. Some animals may have normal urination but also experience incontinence, as the bladder may fill and empty normally, but urine also leaks through the ectopic ureter. In cases of unilateral ectopic ureter, the contralateral kidney and ureter may be normal, and the animal may have normal bladder function, but still be incontinent. Other clinical signs include perivulvar or preputial dermatitis due to urine scald, and recurrent urinary tract infections. In animals with associated renal dysplasia or hydronephrosis, signs of chronic kidney disease such as polyuria, polydipsia, and weight loss may be present. Physical examination may reveal a distended bladder, but often the bladder is small and contracted due to the constant leakage. In females, vaginal examination may reveal the ectopic ureteral orifice, but this is not always possible without anesthesia.

Differential diagnoses for urinary incontinence in young animals include: 1) Urethral sphincter mechanism incompetence (USMI) - more common in spayed females, typically presents later in life, and responds to medical therapy with phenylpropanolamine or estrogen. 2) Urinary tract infection (UTI) - may cause incontinence, but usually associated with dysuria and pollakiuria; urinalysis and culture are diagnostic. 3) Ureterocele - a cystic dilation of the intramural ureter, which may cause obstruction or incontinence; diagnosed by ultrasound or contrast radiography. 4) Bladder hypoplasia - a small, contracted bladder that cannot store urine; often associated with ectopic ureter. 5) Neurogenic bladder - due to spinal cord disease or trauma; associated with other neurological deficits. 6) Ectopic ureter in males - rare, but should be considered in young male dogs with incontinence. 7) Vaginal stricture or persistent hymen - may cause urine pooling and incontinence. 8) Psychogenic polydipsia - may cause polyuria and secondary incontinence, but not true incontinence. 9) Congenital urethral anomalies such as urethral duplication or hypospadias. 10) Renal disease causing polyuria and secondary incontinence. Definitive diagnosis of ectopic ureter requires imaging studies such as cystoscopy, contrast radiography (excretory urography, retrograde vaginourethrography), or advanced imaging (CT or MRI).

The diagnostic algorithm for ectopic ureter begins with a thorough history and physical examination, including a neurological examination to rule out spinal cord disease. A complete blood count, serum biochemistry, and urinalysis with culture are performed to assess renal function and rule out urinary tract infection. If the animal is incontinent, a urine sample should be obtained by cystocentesis to avoid contamination. Imaging is essential for diagnosis. Abdominal radiographs may reveal a small bladder or evidence of renal abnormalities, but are not diagnostic. Ultrasonography is useful to evaluate the kidneys, ureters, and bladder, and may identify hydroureter, hydronephrosis, or a ureterocele. However, the definitive diagnosis is made by contrast radiography or cystoscopy. Excretory urography (intravenous pyelography) can outline the ureters and their termination, but may be inconclusive in some cases. Retrograde vaginourethrography or urethrography can delineate the urethra and vaginal vestibule, and may show the ectopic ureteral orifice. Cystoscopy is the gold standard, allowing direct visualization of the ureteral orifices and the ectopic opening. In cases where cystoscopy is not available, CT urography or MRI can provide high-resolution images of the urinary tract. Once the diagnosis is confirmed, surgical planning is based on the location and type (intramural vs. extramural) of the ectopic ureter, as well as the presence of concurrent anomalies.

Laboratory findings in ectopic ureter are often unremarkable unless there is concurrent urinary tract infection or renal disease. Complete blood count may show leukocytosis or neutrophilia if there is a secondary infection. Serum biochemistry may reveal elevated blood urea nitrogen (BUN) and creatinine if there is significant renal dysfunction, which can occur with bilateral ectopic ureters or associated renal dysplasia. Electrolyte abnormalities may be present if there is chronic kidney disease. Urinalysis may show dilute urine (low specific gravity) if renal concentrating ability is impaired, and may reveal hematuria, pyuria, or bacteriuria if there is a urinary tract infection. Urine culture should be performed to identify the causative organism and guide antibiotic therapy. In cases of chronic urinary tract infection, a urine culture and sensitivity is essential. Coagulation panel (PT/aPTT) is not routinely indicated unless there is a bleeding disorder or if surgery is planned. Inflammatory biomarkers such as C-reactive protein (CRP) or serum amyloid A (SAA) may be elevated in cases of pyelonephritis or systemic inflammation, but are not specific for ectopic ureter.

Imaging is crucial for the diagnosis and surgical planning of ectopic ureter. Abdominal radiography may show a small, contracted bladder, but is not diagnostic. Excretory urography (intravenous pyelography) is a traditional method that involves intravenous injection of iodinated contrast medium, followed by serial radiographs to visualize the kidneys, ureters, and bladder. In ectopic ureter, the ureter may be seen to bypass the bladder and terminate in the urethra or vagina. However, this technique may be limited by poor visualization due to overlying bowel gas or feces, and may not clearly delineate the exact location of the ectopic orifice. Retrograde vaginourethrography or urethrography involves the injection of contrast medium into the vaginal vestibule or urethra, which can outline the urethra and may show reflux of contrast into the ectopic ureter. Ultrasonography is non-invasive and can identify hydroureter, hydronephrosis, and a ureterocele, but may not reliably identify the ectopic orifice. Cystoscopy is the gold standard for diagnosis, allowing direct visualization of the bladder and urethra, and identification of the ectopic ureteral orifice. It also allows assessment of the trigone and the presence of a ureterocele. CT urography or MRI with contrast provides high-resolution, three-dimensional images of the urinary tract, and is particularly useful in complex cases or when cystoscopy is not available. CT urography has been shown to have high sensitivity and specificity for diagnosing ectopic ureter, and can also evaluate the kidneys for concurrent anomalies.

Cytology and histopathology are not typically required for the diagnosis of ectopic ureter, as the condition is a macroscopic anatomical anomaly. However, if a ureterocele is present, aspiration of its contents may yield urine or mucoid fluid. Histopathological examination of the ectopic ureter may be performed after surgical excision or reimplantation, and may show a normal ureteral wall with transitional epithelium, but may also reveal signs of chronic inflammation, fibrosis, or muscular hypertrophy due to chronic urinary reflux or obstruction. In cases of associated renal dysplasia, renal biopsy may show characteristic histopathological features such as persistent metanephric ducts, primitive tubules, and cartilage. These findings are important for prognosis, as renal dysplasia may lead to progressive renal failure. In cases of suspected neoplasia, which is extremely rare in young animals, histopathology would be indicated, but this is not a consideration in typical ectopic ureter cases.

The definitive treatment for ectopic ureter is surgical correction, with the goal of reimplanting the ectopic ureter into the bladder at the normal trigonal position. The surgical approach depends on the type of ectopic ureter (intramural vs. extramural) and its location. For intramural ectopic ureters, a cystotomy is performed, and the ureter is dissected from its ectopic location, preserving its blood supply. The ureter is then reimplanted into the bladder using a submucosal tunnel technique to prevent reflux. For extramural ectopic ureters, the ureter is transected at its ectopic insertion and reimplanted into the bladder. In cases of bilateral ectopic ureters, both ureters are corrected in a single surgery. Preoperative stabilization includes correction of any urinary tract infection with appropriate antibiotics, and management of any renal dysfunction. The surgical technique involves a ventral midline celiotomy, followed by a cystotomy. The bladder is opened, and the ectopic ureteral orifice is identified. For intramural ureters, the ureter is dissected from the bladder wall, and a new opening is created in the trigone. The ureter is then pulled through a submucosal tunnel and sutured to the bladder mucosa using fine absorbable suture material (e.g., 4-0 or 5-0 polydioxanone or polyglactin 910). For extramural ureters, the ureter is transected and reimplanted directly into the bladder using a similar technique. Postoperative care includes pain management, antibiotics, and monitoring for complications such as urine leakage, stricture, or persistent incontinence. In cases where the bladder is hypoplastic, the prognosis for continence may be guarded, and additional medical therapy with phenylpropanolamine or estrogen may be needed. In severe cases, urinary diversion procedures such as ureterocolonic anastomosis or cystostomy tube placement may be considered, but these are rarely necessary.

The prognosis for ectopic ureter is generally good to excellent for resolution of urinary incontinence, with reported success rates of 70-90% for achieving continence after surgical correction. Factors that influence prognosis include the type of ectopic ureter (intramural vs. extramural), the presence of concurrent urogenital anomalies, the degree of bladder development, and the presence of renal disease. Intramural ectopic ureters have a better prognosis than extramural, as they are more amenable to surgical correction. The presence of a hypoplastic bladder is a negative prognostic indicator, as it may not have the capacity to store urine normally. Concurrent renal dysplasia or hydronephrosis may lead to chronic kidney disease, which can affect long-term survival. Postoperative complications include urine leakage, ureteral stricture, and persistent incontinence. Persistent incontinence may occur in up to 30% of cases, and may be due to concurrent urethral sphincter mechanism incompetence, which can be managed medically. Overall, the long-term prognosis for quality of life is good, with most animals achieving acceptable continence with or without medical management.

Postoperative follow-up for ectopic ureter surgery is essential to monitor for complications and assess renal function. The animal should be hospitalized for 24-48 hours postoperatively for pain management and monitoring of urine output. A urinary catheter may be placed during surgery and removed within 24 hours. The incision should be checked daily for signs of infection or urine leakage. Suture removal is typically 10-14 days postoperatively. A urinalysis and urine culture should be performed 2-4 weeks postoperatively to rule out urinary tract infection. Serum biochemistry should be checked to monitor renal function, especially in animals with pre-existing renal disease. Imaging, such as ultrasonography or contrast radiography, may be repeated at 4-8 weeks postoperatively to assess ureteral patency and bladder healing. Restricted activity is recommended for 4-6 weeks to allow proper healing. Physical therapy, such as controlled leash walks, can be initiated after the initial healing period. Long-term follow-up should include regular monitoring for urinary incontinence, as some animals may develop delayed incontinence due to urethral sphincter mechanism incompetence. In such cases, medical therapy with phenylpropanolamine (1-2 mg/kg PO q8-12h) or estrogen (diethylstilbestrol 0.1-1 mg/dog PO q24h) may be initiated. Annual urinalysis and serum biochemistry are recommended to monitor for urinary tract infections and renal function.

Clinical pearls: 1) Always perform a thorough diagnostic workup, including cystoscopy or CT urography, to accurately identify the type and location of the ectopic ureter. 2) In female dogs, a vaginal examination under anesthesia may reveal the ectopic orifice, but this is not always reliable. 3) Preserve the blood supply to the ureter during dissection to prevent ischemia and stricture. 4) Create a submucosal tunnel for reimplantation to prevent vesicoureteral reflux. 5) Consider concurrent urethral sphincter mechanism incompetence in animals that remain incontinent postoperatively. 6) In cases of bilateral ectopic ureters, correct both in a single surgery to avoid a second anesthetic episode. 7) Use fine, absorbable suture material (e.g., 4-0 or 5-0 polydioxanone) for ureteral anastomosis to minimize tissue reaction. 8) Place a urinary catheter during surgery to decompress the bladder and aid in identification of the ureteral orifices. 9) Administer perioperative antibiotics to prevent infection, especially if there is a urinary tract infection. 10) Monitor for postoperative urine leakage by observing for subcutaneous swelling or drainage from the incision. Pitfalls: 1) Failure to identify a concurrent ureterocele, which may require marsupialization or excision. 2) Inadequate dissection of the intramural ureter, leading to incomplete correction. 3) Tension on the ureteral anastomosis, which can cause stricture. 4) Accidental ligation of the ureter during surgery. 5) Failure to recognize a hypoplastic bladder, which may require additional medical management. 6) Inadequate postoperative pain management, leading to increased stress and delayed healing. 7) Discharging the animal without proper follow-up instructions, leading to missed complications. 8) Using non-absorbable suture material in the bladder lumen, which can act as a nidus for stone formation. 9) Overlooking a urinary tract infection, which can lead to pyelonephritis. 10) Performing surgery without advanced imaging, leading to incomplete correction of the anomaly.

Perioperative drug protocols for ectopic ureter surgery are based on Plumb's Veterinary Drug Handbook. Preoperative antibiotics: Cefazolin (22 mg/kg IV) administered 30 minutes before incision, and repeated every 90 minutes during surgery. Postoperative antibiotics: Amoxicillin-clavulanic acid (13.75-22 mg/kg PO q12h) for 7-10 days, or based on culture and sensitivity. Analgesics: Preoperative opioid: Hydromorphone (0.05-0.1 mg/kg IV) or Methadone (0.1-0.3 mg/kg IV). Intraoperative: Fentanyl CRI (5-10 mcg/kg/hr IV) for balanced anesthesia. Postoperative: Buprenorphine (0.01-0.02 mg/kg IV or IM q6-8h) or hydromorphone (0.05-0.1 mg/kg IV or IM q4-6h) for 24-48 hours. Non-steroidal anti-inflammatory drugs (NSAIDs): Carprofen (2.2 mg/kg PO q12h) or Meloxicam (0.1 mg/kg PO q24h) for 3-5 days, starting after recovery from anesthesia, provided renal function is normal. Local anesthesia: Epidural morphine (0.1 mg/kg) or lumbosacral epidural with bupivacaine (0.5-1 mg/kg) for intraoperative and postoperative analgesia. Muscle relaxants: Not routinely used, but if needed, diazepam (0.2-0.5 mg/kg IV) or methocarbamol (15-20 mg/kg PO q8h) for ureteral spasm. Chondroprotectants: Not applicable. For persistent incontinence postoperatively: Phenylpropanolamine (1-2 mg/kg PO q8-12h) or diethylstilbestrol (0.1-1 mg/dog PO q24h) for urethral sphincter mechanism incompetence. For urinary tract infection: Antibiotics based on culture and sensitivity, such as enrofloxacin (5-10 mg/kg PO q24h) or amoxicillin-clavulanic acid (13.75-22 mg/kg PO q12h) for 14-21 days. For renal support: If azotemia is present, consider fluid therapy with balanced electrolyte solutions, and possibly mannitol (0.5-1 g/kg IV over 20 minutes) to promote diuresis. Always adjust dosages based on renal function and monitor for adverse effects.

The surgical management of ectopic ureter has evolved significantly over the past few decades. Historically, nephroureterectomy was performed for unilateral ectopic ureters, but this is now reserved for cases with non-functional kidneys. Modern surgical techniques focus on ureteral reimplantation, with success rates for continence reported between 70% and 90%. A landmark study by McLaughlin and Bjorling (1990) reported a 75% success rate for ureteral reimplantation in dogs. More recent studies have evaluated the use of cystoscopy for diagnosis and minimally invasive techniques such as laser ablation of intramural ectopic ureters. A study by Smith et al. (2010) reported that laser ablation was effective in achieving continence in 80% of cases, with fewer complications than open surgery. However, open surgery remains the gold standard for extramural ectopic ureters and cases with concurrent anomalies. A systematic review by Berent et al. (2012) concluded that both open and minimally invasive techniques have similar outcomes, but patient selection is critical. The presence of a hypoplastic bladder is a negative prognostic factor, and adjunctive medical therapy with phenylpropanolamine may be needed in up to 30% of cases. The ACVS consensus statement on urinary incontinence recommends that all animals with suspected ectopic ureter undergo advanced imaging (CT or cystoscopy) for accurate diagnosis and surgical planning. Overall, the evidence supports surgical correction as the treatment of choice, with a good prognosis for resolution of incontinence and preservation of renal function.