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Hydronephrosis in the dog and cat

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Category: Schede
Hits: 10
  • Disciplina: Urologia
  • Specie: Cane e Gatto

DEFINITION

Hydronephrosis is the dilatation, unilateral or bilateral, of the renal pelvis as a result of obstruction of urinary flow.

 

PATHOGENESIS

The obstruction may be congenital or acquired and occur at any part of the urinary tract. The congenital causes include urethral atresia, stenosis, ureteral torsion and ureterocoele: these abnormalities are often associated with an ectopic ureter.1-4 The acquired causes include neoplasms,5-9 the presence of a clot of blood or urinary tract stone, inflammatory masses,10,11 trauma, stenosis12 and accidental surgical ligation of a ureter.13,14

Both kidneys can be affected when the obstruction is in the urethra or involves both ureters: in these cases the greatest risk is the patient’s death following the rapid development of acute post-renal failure. In the case of unilateral obstruction the parenchyma of the affected kidney atrophies because of the compression until becoming, in the most extreme cases, a fibrous sac containing fluid.

 

CLINICAL SIGNS

The clinical signs are very varied and depend on numerous factors such as the anatomical location of the obstruction, the degree to which urinary flow is compromised, the duration of the disorder and the possible presence of a secondary infection. If the obstruction is bilateral the clinical signs are predominantly those due to uraemia and hyperkalaemia. In contrast, in unilateral hydronephrosis there may be no clinical signs at all and the first finding is often an abdominal mass detected by palpation during a routine clinical examination; if the cause is ureteral obstruction, the animal may manifest signs of abdominal and/or lumbar pain.

In chronic cases the animal usually develops polyuria and polydipsia as a consequence of the decreased mass of functioning kidney; in the more advanced cases the patient may be uraemic. Finally, since the urinary stasis resulting from an obstruction is a factor predisposing to the development of infections, the clinical signs may be those typical of a lower urinary tract infection such as strangury, pollakiuria and urinary tenesmus.

 

DIAGNOSIS

Since bilateral hydronephrosis leads rapidly to death (from acute renal failure) the diagnosis must be made quickly (from the history, clinical signs, radiography and biochemistry screen: urea, creatinine, potassium) and treatment commenced promptly. The clinical examination can provide important information: in a patient with obstruction of the lower urinary tract, a full bladder, a mass palpable at the level of the bladder trigone, a notably enlarged prostate, acute flank pain on palpation and increased size of one or both of the kidneys are suggestive of hydronephrosis. When the disorder is unilateral the earliest clinical finding is an abdominal mass and, in this case, the diagnosis is reached through the use of imaging techniques.

Radiographically the affected kidney may be normal sized or small (chronic or mild obstruction) or its volume variably increased, its borders are rounded and the hilar sulcus is less evident. Intravenous urography can show the increase in the size of the renal pelvis as well as the presence of any diverticula. In the more severe cases most of the kidney is radiolucent and only a thin band of functioning, radio-opaque tissue is seen; X-rays performed 24 hours after administration of a contrast agent may show persistent radio-opacity due to the delayed excretion of the dye. In chronic cases, if the damage is extensive, the residual functional tissue is scarce and does not filter the contrast agent, making the diagnosis more difficult.

Ultrasonography, which is often chosen as the diagnostic imaging technique because it is non-invasive, is less discriminatory with respect to intravenous urography,15-17 although very accurate.18 There are distinctive ultrasonographic features such as the presence of anechoic dilatation of the pelvic cavity (pyelectasis) together with flattening of the pelvic recesses. Hydronephrosis is classified on the basis of ultrasound findings into three grades of increasing severity: if the condition is moderate, the pelvic recesses have a mammillated border, but, gradually, as the hydronephrosis progresses, the mammillation is lost and the atrophy of the parenchyma continues until the kidney has the appearance of a septate cystic mass (Figs. 1, 2 and 3).

The cause of the obstruction must be searched for carefully, following the pathway from the ureter to the bladder: in most cases the obstruction is at the bladder neck. Masses or other lesions that involve the ureters may be identified in the retro-peritoneal space. 

 

TREATMENT

Since hydronephrosis is a secondary condition, the treatment consists essentially of removing the cause of the obstruction. Unfortunately, most of the unilateral cases are not diagnosed until the condition has reached a point of no return: in these cases the only feasible treatment is surgery, that is, removal of the affected kidney by nephrectomy.18

 

References

  1. Bebko RL, Prier JE, Biery DN: “Ectopic ureters in a male cat.”  J Am Vet Med Assic. 1977 Oct 15;171(8):738-40.
  2. D’Ippolito P, Nicoli S, Zatelli A: “Proximal ureteral  ectopia causing hydronephrosis in a kitten.” J Feline Med Surg.2006 Dec;8(6):420-3. Epub 2006 Jul 18.
  3. Ross LA, Lamb CR: “Reduction of hydronephrosis and hydroureter associated with ectopic ureters in two dogs after ureterovesical anastomosis”J Am Vet Med Assoc.1990 May 1;196(9):1497-9.
  4. Shires PK, Teer PA, Sparrow JW: “Hydroureter and hydropenhrosis caused by unilateral ureteral ectopia in a male dog”J Am Vet Med Assoc.1980 Jun 1;176(11):1254-6.
  5. Benigni L, Lamb CR et al: “Lymphoma affecting the urinary bladder in tree dogs and a cat.” Vet Radiol Ultrasound. 2006 Oct-Nov;47(6):592-6.
  6. DeschampsJY, Roux FA, Fantinato M, Albaric O: “Ureteral sarcoma in a dog”  J Small Anim Pract. 2007 Dec;48(12):699-701. Epub 2007 Apr 13.
  7. Hattel AL, Diters RW, Snavely DA: “Ureteral fibropapilloma in a dog” J Am Vet Med Assoc. 1986 Apr 15;188(8):873.
  8. Hurov L, Ellett EW, O’Hara PJ: “Bilateral hydronephrosis resulting from a transitional epithelial carcinoma in a dog.” J Am Vet Med Assoc. 1966 Aug 15;149(4):412-7.
  9. Winter MD, Locke JE, Penninck DG: “imagingdiagnosis--urinary obstruction secondary to prostaticlymphoma in a young dog.”Vet Radiol Ultrasound.2006 Oct-Nov;47(6):597-601.
  10. Kanazono S, Aikawa T, Yoshigae Y: “Unilateral hydronephrosis and partial ureteral obstruction by entrapment in a granuloma in a spayed dog. J Am Anim Hosp Assoc.2009 Nov-Dec;45(6):301-4.
  11. Ragni RA, Fews D: “Ureteral obstruction and hydronephrosis in a cat associated with retroperitoneal infarction.” J Feline Med Surg.2008 Jul;10(3):259-63. Epub 2008 Feb 20.
  12. Leib MS, Allen TA, Konde LJ, JokinenMP: “Bilateral hydropenhosis attributabe to bilateral ureteral fibrosis in a cat.” J Am Vet Med Assoc.1988 Mar 15;192(6):795-7.
  13. Ruiz de Gopegui R, Espada Y, Malò N: “Bilaterla hydroureter and hydronephrosis in a nine-year-old female German sheperd dog” J Small Anim Pract.1999 May;40(5):224-6.
  14. Thun R, Smith CW, Goodale RH, McCracken MD, Stowater J: “Iatrogenic hydronephrosis in a bitch” J Am Vet Med Assoc.1975 Sep 1;167(5):388-90.
  15. Cartee RE, Selcer BA, Patton CS: “Ultrasonographic diagnosis of renal disease in small animals.” J Am Vet Med Assoc.1980 Mar 1;176(5):426-30.
  16. D’Anjou MA, Bédard A, Dunn ME: !Clinical significance of renal pelvic dilatation on ultrasound in dogs and cats.” Vet Radiol Ultrasound.2011 Jan-Feb;52(1):88-94.
  17. Konde LJ, Park RD, Wrigley RH, Lebel JL: “Comparison of radiography and ultrasonofraphy in the evaluation of renal lesions in the dog” J Am Vet Med Assoc.1986 Jun 15;188(12):1420-5.
  18. Dodd GD 3rd, Kaufman PN, Bracken RB: “Renal arterial duplex Doppler ultrasound in dogs with urinary obstruction.”J Urol.1991 Mar;145(3):644-6.

 

Letture consigliate

  1. BSAVA Manual of Canine and Feline Nephrology and Urology Second edition, Edited by Johnathan Elliot and Gregory F. Grauer, 2007.
  2. OsborneCA, Finco DR: Canine and feline nephrology and urology. Williams & Wilkins, Philadelphia, 1995