Contributors: Phil Nicholls, Lori Ludwig, Aidan B McAlinden

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading

Introduction

  • Cause: urolithiasis, trauma, neoplasia (intra-luminal or extra-luminal), iatrogenic intervention, stricture, granulomatous urethritis.
  • Signs: stranguria, dysuria, hematuria or variable flow.
  • Diagnosis: clinical signs, radiography, cystoscopy, biopsy.
  • Treatment: priority is to correct metabolic anomalies, divert urine and stabilize animal prior to definitive management.
  • Prognosis: depends on cause and extent of renal damage.

Presenting Signs

  • Difficulty and straining associated with urination.
  • Variable urine flow.
  • Abdominal enlargement due to bladder distension or secondary to uroabdomen if bladder rupture Bladder: trauma rupture.
  • Lethargy → collapse.

Acute Presentation

Breed Predisposition

Special Risks

  • Males predisposed to obstruction.

Pathogenesis

Etiology

  • Urolithiasis.
  • Trauma, eg os penis fracture.
  • Neoplasia.
  • Iatrogenic intervention.
  • Strangulation of penis or penile foreign body.
  • Bladder herniation Bladder: herniation.

Predisposing Factors

General

  • Urethral stricture following trauma or surgery.
  • Urinary tract infection associated with struvite urolithiasis.
  • Bladder neoplasia most common in bitches.
  • Hypercalcemia Hypercalcemia: overview → calcium oxalate uroliths.

Pathophysiology

  • Obstruction of normal flow of urine leads to:
    • Dilation of kidney calyces and collecting ducts: reduced renal blood flow and glomerular filtration rate.
    • Hydronephrosis and hydroureter Hydronephrosis / hydroureter.
    • Impaired secretion and resorption: azotemia Azotemia , hyperkalemia, metabolic acidosis Acid base imbalance.
    • Increased pressure: ischemia with or without superimposed infection; permanent kidney damage. (Severity depends on degree, duration and level of obstruction with or without presence of infection.)

Timecourse

  • Complete obstruction usually results in death in 3-5 days if untreated.
  • Signs of uremia Uremia develop if complete obstruction present for 48 hours.

Diagnosis

Presenting Problems

Client History

  • Difficulty and straining associated with urination.
  • Licking vulva/penis.
  • Variable urine flow: may cease midstream, continuous slow dribble, non-productive.
  • Hematuria.

Clinical Signs

  • Large bladder, unable to express.
  • Uroliths/masses may be palpated per rectum or externally.

Diagnostic Investigation

Other

Radiography

  • See abdominal radiography Radiography: abdomen
  • Presence of radiopaque calculi in urethra Urethra calculi (male) - radiograph lateral Urethra urolithiasis 01 - radiograph lateral.
  • Extra-urethral mass.
  • Old fractured os penis with callus.

Contrast radiography

  • Retrograde urethrogram:
    • Demonstration of radiolucent or soft tissue lesions Urethra urolithiasis - retrograde urethrogram lateral as filling defects.
  • Intravenous urogram (IVU) Radiography: intravenous urography:
    • May see hydronephrosis or hydroureter if prolonged obstruction to outflow.
    • Estimate of renal function.

2-D Ultrasonography

  • Demonstration of radiolucent or soft tissue lesions in urethra Ultrasonography: bladder and urinary tract.
  • Hydronephrosis/hydroureter with chronic obstruction.
  • Thickened bladder wall with calculi.
  • Prostatic disease.
  • Neoplasia of trigone or bladder neck.

Biochemistry

Urethroscopy/cystoscopy

Gross Autopsy Findings

  • Urethral examination requires removal of ventral pelvic bones.
  • After removal of ventral muscles, cut cranially and ventrally from obturator foramen bilaterally using bone forceps or saw.
  • Urethral patency can be checked by gentle manual bladder pressure. Open urethra along its full length.
  • May see proximal dilation and secondary hydroureter/hydronephrosis if intermittent or incomplete obstruction.
  • Inspect for signs of post-inflammatory fibrosis and structure, compression by intramural or extramural space-occupying lesions.
  • Check for neoplasia Urethra transitional cell carcinoma 01 - pathology.
  • Fix samples of urethra, bladder, ureter, kidney, cause of obstruction (prostate, mass, etc).
  • If litigation possible, eg accidental surgical ligation, photograph dissection carefully and save entire urethra in formalin.

Histopathology Findings

  • Depends on the cause, but may see inflammation and fibrosis at sites of stricture.
  • Identification of neoplasm, eg transitional cell carcinoma.
  • Lymphocytic, plasmacytic urethritis.

Differential Diagnosis

Treatment

Initial Symptomatic Treatment

  • Correct acid/base, electrolytes.
  • Establish diuresis.
  • Drain bladder by cystocentesis Cystocentesis , or place temporary tube cystostomy Cystostomy: tube.
  • Urinary catheterization with retrograde urohydropulsion of calculi Urethra: retrograde urohydropulsion.
  • Urethrotomy if calculi lodged at base of penis and cannot be dislodged by retrograde urohydropulsion.

Standard Treatment

Urolithiasis

  • Stabilize animal.
    Either Attempt conservative management by catheterization or retrograde urohydropulsion of calculus into bladder and remove by cystotomy Cystotomy.
    Or Remove calculus by urethrotomy Urethrotomy.

Neoplasia

  • Depends on tumor type.
  • Often malignant and aggressive TCC of trigone, bladder neck, proximal urethra Urethra: neoplasia.
  • Extra-luminal compression of pelvic urethra from prostatic neoplasia in males.
  • Palliative stenting can produce immediate improvement in ability to pass urine.
  • Can be associated with a fair to good outcome.

Monitoring

  • Monitor electrolytes (Na+ and K+ Blood biochemistry: sodium Blood biochemistry: potassium ), acidosis, hydration.
  • Post-obstructive diuresis may result in dehydration and hypokalemia if not adequately monitored/supplemented.
  • Monitor urine output (aim >1 ml/kg/hr).
  • Monitor for repeat obstruction.

Outcomes

Prognosis

  • Depends on underlying cause, duration and severity of obstruction.

Expected Response to Treatment

  • Ability to definitively treat underlying cause.
  • Resolution of metabolic derangements.

Reasons for Treatment Failure

  • Urinary tract rupture from traumatic catheterization.
  • Delay in treatment.
  • Inability to remove all calculi.
  • Malignant neoplasia.

Further Reading

Publications

Refereed papers

Other Sources of Information