Contributors: Phil Nicholls, Lori Ludwig, Aidan B McAlinden
Species: Canine | Classification: Diseases
- 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).
- Males predisposed to obstruction.
- Trauma, eg os penis fracture.
- Iatrogenic intervention.
- Strangulation of penis or penile foreign body.
- Bladder herniation Bladder: herniation.
- 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.
- Large bladder, unable to express.
- Uroliths/masses may be palpated per rectum or externally.
- Urethral catheterization Urethral catheterization: female Urethral catheterization: male :
- Confirms diagnosis of urethral obstruction.
- Reveals level of obstruction.
- See abdominal radiography Radiography: abdomen
- Presence of radiopaque calculi in urethra .
- Extra-urethral mass.
- Old fractured os penis with callus.
- Retrograde urethrogram:
- Intravenous urogram (IVU) Radiography: intravenous urography:
- May see hydronephrosis or hydroureter if prolonged obstruction to outflow.
- Estimate of renal function.
- 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.
- To assess degree of renal insufficiency/failure:
- Especially useful in females Cystoscopy: transurethral cystoscopy/vaginoscopy.
- Flexible urethroscopy possible in large breed dogs.
- Can visualize lesion and biopsy if neoplastic.
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 .
- 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.
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.
- 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.
- 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.
- 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.