Contributors: Lori Ludwig, Julien Bazelle
Species: Canine | Classification: Diseases
- 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).
- 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.
- Reflex dyssynergia Dyssynergia most commonly occurs in large and giant-breed male dogs.
- Intraluminal: urolithiasis Urolithiasis; pyelonephrosis.
- Spinal disease.
- Reflex dyssynergia.
- 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.
- 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.
- Correction of ureter obstruction within 7 days: little permanent damage.
- Complete urethral obstruction results in death in 3-5 days.
- 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.
- In severe cases the owner may report:
- 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.
- Abdominal radiography Radiography: abdomen : some uroliths may be seen on plain films.
- Neoplasia (if normal ).
- Prostatomegaly .
- Excretory urography to evaluate kidneys and ureters Radiography: intravenous urography.
- Positive contrast urethography and double contrast urethography are best for evaluating lower urinary tract Radiography: double contrast cystography.
- Useful to detect cystic calculi masses in the bladder Ultrasonography: bladder and urinary tract.
- To assess the prostate in small dogs.
- To evaluate hydronephrosis, hydroureter.
- High definition of lesions.
- Possibility to perform CT urography.
Gross Autopsy Findings
- The following may be present:
- 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:
- Calculi .
- Prostatic hyperplasia Prostate: benign hyperplasia and hypertrophy or neoplasia Prostate: neoplasia.
- Space occupying lesions in the pelvic cavity.
- Perineal hernia (bladder malposition) Bladder: herniation.
- Neoplasia .
- Malposition of kidneys (pelvic).
- Iatrogenic (ligation of ureters during ovariohysterectomy).
- 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).
- Depends on the cause.
- Urinary obstruction causes:
- Tubular atrophy.
- Interstitial edema.
- 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.
- For cause of obstruction - see etiology (intraluminal, intramural, extramural, functional).
- For dysuria/stranguria other than above:
- Perineal hernia.
- Inflammation/urethrospasm from prolonged or traumatic catheterization.
- Urinary tract rupture.
Initial Symptomatic Treatment
Treatment should involve
- Relief of obstruction/decompression of bladder for urethral obstruction:
- Relief of obstruction/decompression of ureteral obstruction:
- Medical treatment with pain relief, muscle relaxants Muscle relaxant: overview.
- Emergency surgery.
- Evaluation and treatment of:
- Metabolic acidosis Acid base imbalance.
- Definitive diagnosis and treatment of underlying cause.
- See also urolithiasis Ureter: urolithiasis.
- See also neoplasia of ureter Ureter: neoplasia.
- After relief of the obstruction the patient should be monitored for:
- Adequate urine production (>1 ml/kg/h).
- PCV Hematology: packed cell volume /TS Blood biochemistry: total protein /K+ Blood biochemistry: potassium/creatinine Blood biochemistry: creatinine/BUN Blood biochemistry: urea to monitor resolution of initial metabolic derangements (patients may become hypokalemic and have a post-obstructive diuresis).
- ECG if previous cardiac problems.
- 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.
- 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).
- 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.
- 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.