Ureteral atresia

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Characteristic macroscopic appearance of congenital ureteral atresia in a mouse[1]

Congenital ureteral atresia is a ureteral disease of dogs characterized by a blind-ending ureter anywhere between the ureteropelvic junction (kidney) and ureterovesicular junction (bladder)[2].

In distal atresia, the ureter fails to communicate with the bladder and terminates close to it as a cul-de-sac. Proximal atresic ureters generally presents as a cystic mass[3].

This disease usually occurs unilaterally, and less commonly, bilaterally in dogs, and is observed secondary to renal dysplasia[4], renal agenesis[5], ectopic ureters[6] and ureteral duplication, where malformations of the mesonephric duct (Wolffian duct) results in deformed ureteral buds[7].

It can also occur secondary to pyelonephritis, penetrating wounds[8] or ovariohysterectomy[9], leading to ureteral trauma, cicatrization, stenosis and atresia.

This rare anomaly is caused by a variable degree of failure of the ureteral bud development.

CLinically affected dogs with congenital ureteral atresia usually present with symptoms referable to chronic renal disease, such as anorexia, poor weight gain, vomiting, renal pain and abdominal distension.

Blood tests may show hyperkalemia and azotemia.

Diagnosis is usually established based on hematological tests (which usually show azotemia and hyperkalemia due to renal dysplasia), urinalysis (hematuria) and diagnostic imaging, including ultrasonography[10] and excretory urography, which usually shows varying degrees of hydronephrosis.

A differential diagnosis would include other causes of hydronephrosis such as ureteroliths, nephroliths, pyelonephritis, urothelial carcinoma, ureteral stenosis, circumcaval ureter, ureteral duplication[11] and ectopic ureter[12].

In congenital atresia, treatment is usually difficult in these cases and the prognosis is usually dependent on the severity of the obstruction.

Surgical techniques associated with secondary atresia include ureterotomy, partial ureterectomy and ureteroneocystostomy, and ureteral resection and anastomosis[13].

Ureteral stenting may be attempted in unilateral cases.

Severely hydronephrotic congenital cases may be resistant to therapy and require euthanasia.

References

  1. Nishimura H et al (1999) Role of the angiotensin type 2 receptor gene in congenital anomalies of the kidney and urinary tract, CAKUT, of mice and men. Mol Cell 3(1):1-10
  2. Lamb CR & Gregory SP (1994) Ultrasonography of the ureterovesicular junction in the dog: a preliminary report. Vet Rec 134(2):36-38
  3. Bhattacharjee PK etal (2004) Distal ureteric atresia presenting as an abdominal lump in an adult. Indian J Surg 66:175-177
  4. Yoon HY et al (2010) Bilateral ureteral ectopia with renal dysplasia and urolithiasis in a dog. J Am Anim Hosp Assoc 46(3):209-214
  5. Agut A et al (2002) Unilateral renal agenesis associated with additional congenital abnormalities of the urinary tract in a Pekingese bitch. J Small Anim Pract 43(1):32-35
  6. Thomas PC & Yool DA (2010) Delayed-onset urinary incontinence in five female dogs with ectopic ureters. J Small Anim Pract 51(4):224-226
  7. Ruano-Gill D et al (1975) Obstruction and normal recanalization of the ureter in the human embryo. Its relation to congenital ureteric obstruction. Eur Urol 1:287–293
  8. Menard J & Schoeffler GL (2011) Colonic, ureteral, and vascular injuries secondary to stick impalement in a dog. J Vet Emerg Crit Care (San Antonio) 21(4):387-394
  9. Ruiz de Gopegui R et al (1999) Bilateral hydroureter and hydronephrosis in a nine-year-old female German shepherd dog. J Small Anim Pract 40(5):224-226
  10. Lamb CR & Gregory SP (1998) Ultrasonographic findings in 14 dogs with ectopic ureter. Vet Radiol Ultrasound 39(3):218-223
  11. Esterline ML et al (2005) Ureteral duplication in a dog. Vet Radiol Ultrasound 46(6):485-489
  12. North C et al (2010) Congenital ureteral ectopia in continent and incontinent-related Entlebucher mountain dogs: 13 cases (2006-2009). J Vet Intern Med 24(5):1055-1062
  13. Hardie EM & Kyles AE (2004) Management of ureteral obstruction. Vet Clin North Am Small Anim Pract 34(4):989-1010