Congenital ureteral abnormalities include ectopic ureters and ureteroceles. Less frequently recognized ureteral anomalies include aplasia and duplication.
Ureteral Ectopia in Animals
Ureteral ectopia is a congenital abnormality in which one or both ureters open in an abnormal location distal to the normal trigonal location. Involved ureters may open into the urethra, uterus, or vagina. Unilateral ectopic ureter occurs with equal frequency on right and left sides, and involvement is bilateral in approximately 25% of cases. Ectopic ureters may be extramural (bypassing the urinary bladder to insert at a distal location) or intramural (entering the serosal surface of bladder in the normal dorsolateral location but traversing in the submucosa to terminate in the distal bladder neck, urethra, or vaginal vestibule). Ectopic ureters generally result from disrupted development of the mesonephric and metanephric duct systems.
Ectopic ureters are frequently associated with other anomalies, including hydroureter, hydronephrosis, renal hypoplasia, bladder hypoplasia, and urethral sphincter incompetence.
Ectopic ureters can affect both dogs and cats. In dogs, it is most commonly reported in 3- to 6-month-olds, with females affected much more frequently than males. The reported prevalence of ectopic ureters in dogs is 0.016%–0.045% (1). This condition is more frequently diagnosed in female dogs possibly because urinary incontinence is more readily identified in females.
Ureteral ectopia is familial in many dog breeds, including Labrador Retrievers, Siberian Huskies, Golden Retrievers, Newfoundlands, and English Bulldogs. A genetic component is suspected in affected West Highland White Terriers, Fox Terriers, Skye Terriers, and Miniature and Toy Poodles.
In horses, ureteral ectopia is the most common congenital anomaly affecting the urinary tract; as in dogs, in horses it is substantially more common in fillies than in colts.
Ectopic ureters are infrequently identified as a clinical problem in cattle, sheep, or pigs.
Continual dripping of urine is the classic clinical sign, although animals with unilateral ectopic ureters may void normally; the inability to void normally suggests bilateral ureteral ectopia. Low-grade vaginitis or vulvitis may also be present due to urine scalding.
Diagnosis is confirmed by ultrasonography or IV urography that traces the course of the ureter to an abnormal location.
Courtesy of Ontario Veterinary College.
Courtesy of Dr. Ajay Sharma.
Successful surgical treatment for ureteral ectopia usually involves either transplantation of affected ureters into the bladder or ureteronephrectomy. A review of surgically repaired ectopic ureters in female dogs indicated that factors including left- or right-sided ectopic ureter, unilateral or bilateral ectopic ureter, presence of hydroureter, and presence of urinary tract infections did not significantly influence postoperative incontinence (2). Another study found that 14 of 30 (47%) female dogs with ectopic ureters treated by cystoscopic-guided laser ablation maintained urinary continence without additional treatment, while another 9 dogs were treated successfully with additional medical management after laser ablation. Overall, urinary continence was maintained in 23/30 (77%) treated dogs (3).
Indications for ureteronephrectomy include severe ipsilateral renal disease such as hypoplasia, hydronephrosis, or pyelonephritis in the presence of a normally functioning contralateral kidney. Important postoperative complications are persistent incontinence, hydronephrosis, and dysuria. Incontinence occurs most often in cases of bilateral ectopic ureters and may be due to abnormal development of the bladder neck and urethra. An adrenergic agent such as phenylpropanolamine (1.5 mg/kg, PO, every 24 hours, longterm) may help minimize incontinence (4).
Ureteroceles in Animals
Ureteroceles are characterized by dilation of the submucosal ureter segment within the bladder.
Diagnosis of ureterocele is by ultrasonographic examination or excretory urography.
Ureteronephrectomy is the appropriate treatment for ureterocele if the lesion is unilateral and there is secondary hydronephrosis and hydroureter. If the proximal ureter and kidney are normal, excision or incision of the ureterocele, in addition to ligation of any ectopic distal channels, has been successful.
References
Dean PW, Bojrab MJ, Constantinescu GM. Canine ectopic ureter. Compend Contin Educ Vet. 1988;10(2):146–162.
Ho LK, Troy GC, Waldron DR. Clinical outcomes of surgically managed ectopic ureters in 33 dogs. J Am Anim Hosp Assoc. 2011;47(3):196-202. doi:10.5326/JAAHA-MS-5495
Berent AC, Weisse C, Mayhew PD, Todd K, Wright M, Bagley D. Evaluation of cystoscopic-guided laser ablation of intramural ectopic ureters in female dogs. J Am Vet Med Assoc. 2012;240(6):716-725. doi:10.2460/javma.240.6.716
Baines SJ, Speakman AJ, Williams JM, Cheeseman MT. Genitourinary dysplasia in a cat. J Small Anim Pract. 1999;40(6):286-290. doi:10.1111/j.1748-5827.1999.tb03081.xC
