Contributors: Lori Ludwig, Julien Bazelle

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Cause: urolithiasis, mass, prostatic disease, pyelonephritis, proliferative urethritis, iatrogenic ligation of ureters during spay, stricture, dyssynergia.
  • Signs: dysuria, stranguria, hematuria, lethargy, anorexia, signs of renal disease, abdominal pain.
  • Diagnosis: signs, urinalysis, imaging.
  • Treatment: catheterize, balloon dilation, stenting or surgically remove urethral obstructions; medical treatment, ureteral stents, subcutaneous ureteral bypass devices or surgery for ureteral obstruction.
  • Prognosis: dependent on underlying cause:
    • Neoplasia (grave).
    • Urolithiasis, urethritis, dyssynergia, prostatic disease (good if treatment initiated promptly).

Presenting Signs

  • Dysuria Dysuria investigation, hematuria Hematuria, stranguria or tenesmus for urethral obstruction.
  • Abdominal pain, turbid urine, hematuria, signs of post-renal renal failure for ureteral obstruction, especially if bilateral. 
  • Anuria.

Acute Presentation

Breed Predisposition

  • Breed-related risk for urolithiasis: Dalmatian Dalmatian with urates, English Bulldog Bulldog with cysteine. 

Special Risks

  • Reflex dyssynergia Dyssynergia most commonly occurs in large and giant-breed male dogs.

Pathogenesis

Etiology

Predisposing Factors

General

  • Male dogs more frequently obstruct secondary to urolithiasis.
  • Struvite urolithiasis and proliferative urethritis most commonly associated with infection.
  • Urethral neoplasia is more common in female dogs.
  • Specific breed disposition, eg Dalmatian/urate, for urolithiasis.
  • Reflex dyssynergia most commonly occurs in large and giant-breed male dogs. 

Pathophysiology

  • Urethral obstruction Urethra: obstruction commonly occurs in dogs as a result of urolithiasis, neoplasia or trauma.
  • Acute urethral obstruction is seen most commonly in male dogs due to obstruction by calculi lodged at the base of the os penis.
  • Prolonged ureteric obstruction Ureter: urolithiasis (>7 days in experimental studies) → dilation of proximal segment and hydronephrosis Hydronephrosis / hydroureter , eg correction of obstruction at 4 weeks: renal function 25% of normal.
  • If obstruction is relieved within 7 days - little permanent damage in experimental studies.
  • Complete urethral obstruction can result in hydroureter, hydronephrosis, and bladder rupture → azotemia, hyperkalemia, acidosis.

Timecourse

  • Days.
  • Correction of ureter obstruction within 7 days: little permanent damage.
  • Complete urethral obstruction results in death in 3-5 days.

Diagnosis

Presenting Problems

  • The presenting clinical signs and pathophysiology depend on the site, degree, and duration of obstruction.
  • Complete obstruction results in life threatening uremia Uremia, and may progress to rupture of the urinary tract.

Client History

  • Stranguria.
  • Pollakiuria.
  • Hematuria.
  • In severe cases the owner may report:
    • Vomiting.
    • Lethargy.
    • Anorexia.

Clinical Signs

  • Urethral obstruction: large bladder - unable to express.
  • May be able to palpate uroliths, masses or pelvic fractures, per rectum.
  • Collapse, hypothermia, bradycardia, abdominal pain, or ventricular tachycardia secondary to hyperkalemia Hyperkalemia.

Diagnostic Investigation

Radiography 

  • Abdominal radiography Radiography: abdomen : some uroliths Bladder calculi - cystogram Ureter calculi - radiograph Urethra calculi (male) - radiograph lateral may be seen on plain films.
  • Neoplasia Urethra calculi (male) - radiograph lateral Urethra neoplasia  stricture -  retrograde vaginourethrogram (if normal Urethra normal retrograde urethrogram (male) - lateral Urethra normal retrograde vaginourethrogram (female) - lateral ).
  • Prostatomegaly

Contrast radiography

2-D Ultrasonography

Computed tomography

  • High definition of lesions. 
  • Possibility to perform CT urography.

Gross Autopsy Findings

  • The following may be present:
    • Hydronephrosis.
    • Hydroureter.
    • Secondary urinary tract infection Cystitis.
    • Bladder distension or rupture.
    • Prostatic disease.
    • A complete examination of urethra is required, may need opening along its full length through the prostate and penis in the male.
  • Check for:
  • Anuria may also be due to intrinsic renal disease, eg acute tubular necrosis, so examine kidneys carefully and fix samples for histology.
  • Chronic unilateral urinary obstruction may cause renal atrophy. Contralateral kidney may show compensatory hypertrophy.
  • Secondary infection of hydronephrotic kidney causes pyonephrosis (pus-filled dilated kidney).

Histopathology Findings

  • Depends on the cause.
  • Urinary obstruction causes:
    • Tubular atrophy.
    • Apoptosis.
    • Interstitial edema.
    • Fibrosis.
    • Dilation of proximal convoluted tubules.
  • There may be inflammation if secondary infection has occurred.
  • Glomeruli often persist among fibrous remains of cortex.
  • Proliferative urethritis was associated with lymphocytic-plasmacytic, or neutrophilic inflammation and was frequently associated with positive fluorescence in situ hybridization (FISH) results. 

Differential Diagnosis

  • For cause of obstruction - see etiology (intraluminal, intramural, extramural, functional).
  • For dysuria/stranguria other than above:
    • Constipation.
    • Perineal hernia.
    • Inflammation/urethrospasm from prolonged or traumatic catheterization.
    • Urinary tract rupture.
    • Behavioral.

Treatment

Initial Symptomatic Treatment

Treatment should involve

  • Relief of obstruction/decompression of bladder for urethral obstruction:
  • Relief of obstruction/decompression of ureteral obstruction: 
  • Evaluation and treatment of:
  • Definitive diagnosis and treatment of underlying cause.

Standard Treatment

Intraluminal

Intramural

Monitoring

Subsequent Management

Treatment

  • Chemotherapy for neoplasia.
  • Antibiotics for proven urinary tract infections, pyelonephritis Kidney: pyelonephritis. May be needed for proliferative urethritis. 
  • Muscle relaxants (eg prazosin Prazosin, terazosin, phenoxybenzamine Phenoxybenzamine), pain reliefs (eg opioids) for ureteral obstruction and dyssynergia. 
  • Surgical or chemical castration for prostatic diseases. 
  • Balloon dilation or stenting have been described for benign or malignant urethral obstruction. 
  • Ureteral stenting or subcutaneous ureteral bypass devices have been used in patients with ureteral obstructions. 
  • Surgery may be necessary for some causes.

Monitoring

  • Monitor for recurrence uroliths (following cystotomy for uroliths). Preventive urinary diets may be recommended. 
  • Monitor for subsequent stricture using excretory urography, ultrasonography, at 4 and 8 weeks (for trauma to ureter or calculi in ureter).

Outcomes

Prognosis

  • Complete obstruction of the urethra usually results in death in 3-5 days without treatment.
  • Ureteroliths can pass without surgical intervention.
  • In experimental studies: <7 days obstruction ureter: little permanent damage.
  • >7 days obstruction ureter: permanent kidney damage likely, eg 25% renal fuction after 4 weeks.
  • Chronic obstruction ureter: may lead to ureteral rupture/urine leakage/retroperitonitis. See also trauma of ureter Ureter: trauma.

Expected Response to Treatment

  • Adequate urine production with resolution of uremia, electrolyte abnormalities, and underlying cause.

Reasons for Treatment Failure

  • Rupture of urinary tract due to aggressive catheterization or neglect of obstructed patient.
  • Stricture of the ureter or urethra as previous site of trauma, surgery, calculi.
  • Inability to control the cause. 
  • Secondary urinary tract infection. 

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Caywood D D, Osbourne C A (1986) Surgical removal of canine uroliths. Vet Clin North Am Small Anim Pract 16 (2), 389-407 PubMed.
  • Osbourne C A, Polzin D J (1986) Non-surgical management of canine obstructive urolithopathy. Vet Clin North Am Small Anim Pract 16 (2), 333-347 ScienceDirect.
  • Ibrahim A, Musa B, Zein M (1984) Changes in urinary pH and glomerular filtration rate in partially obstructed canine kidney. J Urol 131 (1), 143-145 PubMed.

Other sources of information

  • Stone E A (1992) Urologic Surgery of the Dog and Cat. Philadelphia: Lea & Febiger.

Other Sources of Information