Urethra: obstruction

• 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.

• 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.

• Depression or vomiting associated with acute renal failure Kidney: acute kidney injury (AKI).

• Dalmatians Dalmatian: urate calculi .
• Schnauzers Schnauzer: Standard: calcium oxalate calculi.

• Males predisposed to obstruction.

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

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.

• 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.)

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

• Dysuria/anuria/hematuria Hematuria.

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

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

Other

• Urethral catheterization Urethral catheterization: female Urethral catheterization: male :
  • Confirms diagnosis of urethral obstruction.
  • Reveals level of obstruction.

Radiography

• See abdominal radiography Radiography: abdomen
• Presence of radiopaque calculi in urethra  .
• Extra-urethral mass.
• Old fractured os penis with callus.

Contrast radiography

• Retrograde urethrogram:
  • Demonstration of radiolucent or soft tissue lesions  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

• To assess degree of renal insufficiency/failure:
  • Reduced renal blood flow and glomerular filtration rate Fractional electrolyte excretion , azotemia, hyperkalemia Blood biochemistry: potassium , metabolic acidosis.

Urethroscopy/cystoscopy

• Especially useful in females Cystoscopy: transurethral cystoscopy/vaginoscopy.
• Flexible urethroscopy possible in large breed dogs.
• Can visualize lesion and biopsy if neoplastic.

• 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 .
• 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.

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

• Acute renal failure Kidney: acute kidney injury (AKI).
• Bladder rupture traumatic Bladder: trauma rupture.
• Perineal hernia Perineum: rupture.
• Constipation.
• Neurogenic.
• Urethrospasm/inflammation from prolonged or traumatic catheterization.
• Reflex dyssynergia.

• 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.

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.

• 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.

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

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

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

Refereed papers

• Recent references from PubMed and VetMedResource.