Urethra: obstruction

• Causes: urolithiasis, urethral plugs, trauma, neoplasia, extra-urethral mass, idiopathic inflammation, iatrogenic intervention.
• Signs: straining (stranguria)     and difficulty associated with urination/variable flow.
• Diagnosis: clinical signs and physical examination.
• Treatment: priority is to correct metabolic abnormalities and stabilize animal prior to definitive management.
• Prognosis: depends on cause and extent of renal damage.

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• Difficulty and straining associated with urination  .
• Variable urine flow.

• Hematuria Hematuria.
• Signs may be interpreted as straining to defecate by some owners.

Chronic untreated case

• Depression.
• Lethargy.
• Coma.
• Vomiting.

• Extreme discomfort - distended bladder.

• Prolonged obstruction   →   hyperkalemia   →   cardiac arrythmias .

• Urolithiasis Urolithiasis, urethral matrix-crystalline plugs.
• Trauma.
• Neoplasia Urethra: neoplasia.
• Extra-urethral mass.
• Iatrogenic intervention.

Specific

• Urolithiasis: structure of male urethra.

• Feline urethral obstruction is (unlike canine) often complete and is an urgent situation.
• Most obstructions occur at the distal penile urethra or the membranous urethra.

• Obstruction of normal flow of urine leads to:
  • Dilation of kidney calyces and collecting ducts: reduced renal blood flow and glomerular filtration rate.
  • Impaired excretion: azotemia Azotemia, hyperkalemia Hyperkalemia, metabolic acidosis Acid base imbalance.
  • Increased pressure: renal ischemia with or without superimposed infection; permanent kidney damage (severity depends on degree, duration and level of obstruction with or without presence of infection.).
• Hyperkalemia may   →   cardiac arrythmias   →   death.

• Bladder distention will reach critical proportions within hours of a complete blockage.

• Dysuria/anuria Dysuria investigation.
• Hematuria Hematuria.

• Difficulty and straining (stranguria, dysuria) associated with urination.
• Variable urine flow: may cease midstream, continuous slow dribble, non-productive.
• Bleeding from urethra.
• Hematuria.
• Increased frequency of micturition/attempts to urinate.
• Frequent licking of genital area.
• Urination in abnormal places.
• Vomiting.
• Depression.
• Coma.

• Distended bladder palpable; cannot express urine with gentle pressure.

Other

• Urethral catheterization Urethra: catheterization reveals level of obstruction and often allows relief of obstruction by retrohydropulsion.

Radiography

• See abdominal radiography Radiography: abdomen.
• Presence of radiopaque calculi      .
• Extra-urethral mass.

Contrast radiography

• Retrograde urethrography Radiography: urethrography:
  • Demonstration of radiolucent uroliths or soft tissue lesions.

2-D Ultrasonography

• See ultrasonography of the bladder and urinary tract Ultrasonography: bladder and urinary tract.
• Demonstration of radiolucent or soft tissue lesions  .

Biochemistry

• To assess degree of postrenal and renal azotemia: reduced renal blood flow and glomerular filtration rate   →   azotemia Blood biochemistry: urea, hyperkalemia Blood biochemistry: potassium, metabolic acidosis.

• Urolithiasis Urolithiasis; urethral matrix-crystalline plug.
• Idiopathic cystitis/urethritis Idiopathic cystitis.
• Iatrogenic intervention.
• Urethral trauma Urethra: rupture.
• Urethral neoplasia Urethra: neoplasia.
• Extraluminal mass.

• Place intravenous catheter and start IV fluid therapy (eg 0.9% saline).
• Correct acid/base, electrolytes Fluid therapy: for acid-base imbalance Fluid therapy: for electrolyte abnormality.
• Tranquilize or anesthetize (as high risk patient). Anesthesia preferred as it provides better urethral relaxation.
• Attempt to pass a urethral catheter:
  • An end-opening, non traumatic catheter should be used.
  • Ideally 3.5 F.
  • Extrude penis and place catheter in penile tip.
  • Gently extend penis in caudal and dorsal direction - this will straighten the urethra and ease passage of the catheter.
  • Flush catheter with sterile saline and attempt to advance it.
  • Gentle urethral massage per rectum can sometimes assist in displacing a urolith/urethral plug.
  • If the catheter cannot be advanced retrograde urohydropulsion can be attempted.
  • Gently occlude the urethra proximal to the obstruction per rectum.
  • Infuse saline until the urethra distends under pressure.
  • Release the occlusion to help flush urolith/plug into the bladder.
• If urethral catheterization fails, drain urinary bladder by cystocentesis Cystocentesis and attempt to relieve urethral obstruction again.
• If urethral catheterization fails, consider temporary tube cystostomy to drain bladder Cystostomy: tube.

• Stabilize animal.
• Place urethral catheter Urethra: catheterization.
  There is some controversy about whether this should be left in situ.
• If leaving a catheter in situ then it should be exchanged for one of a soft silicon variety.
• See Urolithiasis Urolithiasis.

• Body temperature.
• Fluid balance.
• Electrolytes, acid/base.
• Azotemia.

Monitoring

• Urinary bladder size.
• Fluid balance, electrolytes, acid/base.
• Azotemia.
• Urine output.

• Good prognosis for early treatment.
• Urolithiasis has a high incidence of recurrence, without dietary changes.

• Ability to pass urine normally.
• Resolution of uremia and electrolyte abnormalities if present.

• Delayed treatment allowing renal failure to develop lin Kidney: acute renal failure.
• Inability to remove blockage.
• Stenosis recurring at site of trauma, urolith, or urethral tear.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Gerber B, Eichenberger S & Reusch C E (2008) Guarded long-term prognosis in male cats with urethral obstruction. J Fel Med Surg 10 (1), 16-23 PubMed.
• Lee J A & Drobatz K J (2003) Characterization of the clinical characteristics, electrolytes, acid-base, and renal parameters in male cats with urethral obstruction. J Vet Emerg Crit Care 13 (4), 227-33 VetMedResource.
•  Foster S F, Hunt G B & Malik R (1999) Congenital urethral anomaly in a kitten. J Feline Med Surg 1 (1), 61-64 PubMed.