PATHOLOGY - Urethral Obstruction Flashcards
What is a urethral obstruction?
A urethral obstruction is where there is an obstruction of the urethra, preventing urination
Why are male animals more prone to urethral obstructions?
Male animals have a longer urethra and there is considerable narrowing of the urethral lumen at the os penis in male dogs and cats
What are the potential causes of urethral obstruction in dogs?
Urolithiasis
Urethritis
Retroflexed bladder into a perineal hernia
Prostatic disease
Urethral spasm
Neoplasia
What is the most common cause of urethral obstruction in dogs?
Urolithiasis
Which signalement is most prone to urethral obstruction?
Young, male cats
What are the potential causes of urethral obstruction in cats?
Feline idiopathic cystitis
Urolithiasis
Urethral stricture
Prostatic disease
Neoplasia
What is the most common cause of urethral obstruction in cats?
Feline idiopathic cystitis
How does feline idiopathic cystitis cause urethral obstruction?
Feline idiopathic cystitis can result in the formation of urethral plugs or cause urethral spasm resulting in urethral obstruction
What are the clinical signs of a urethral obstruction?
Dysuria
Stranguria
Pollakuria
Haematuria
Large, tense bladder on palpation
Posturing to urinate
Urine dripping
Can be bright to lethargic/collapsed
What should you make sure to assess on clinical examination of a patient with a potential urethral obstruction?
Abdominal palpation to feel the bladder
Assess the penis
Rectal examination
Why is it important to assess the penis in patients with a potential urethral obstruction?
You should assess the penis as there may be a distal plug or urolith that can be removed
Why is it important to do a rectal examination in patients with a potential urethral obstruction?
You should do a rectal examination as neoplasia and prostatic disease can cause compression of the urethra and this can be felt via the rectum
Which diagnostic tests should you do when presented with a patient with urethral obstruction?
Urinalysis and culture
Haematology and biochemistry
Diagnostic imaging
What should you assess on haematology and biochemistry in patients with urethral obstruction?
Assess renal funtion
Assess potassium levels
Assess for any other underlying causes of obstruction
Which diagnostic imaging can you do in patients with a urethral obstruction?
Ultrasound
Radiography
Contrast radiography
What are the three main consequences of urethral obstruction?
Post-renal azotaemia
Hyperkalaemia
Metabolic acidosis
What is the first thing you should do when treating a urethral obstruction?
Stabilise the patient
How do you treat a urethral obstruction?
Analgesia
Intravenous fluid therapy
Manage hyperkalaemia
Relieve the urethral obstruction
Which analgesia should you provide patients with a urethral obstruction?
Full μ agonst opioid as the patient will possibly have to go for surgery and it is a very painful condition
Why should you avoid NSAIDs in patients with a urinary obstruction?
Patients with urethral obstruction are usually both hypovolaemia and have reduced renal perfusion so NSAIDs are contraindicated
What are the purposes of intravenous fluid therapy when treating a urethral obstruction?
Manage post-renal azotaemia
Increase renal perfusion
Correct hyperkalaemia
Which fluids should you use when treating a urethral obstruction?
Isotonic crystalloid fluids
What is one of the main consequences of hyperkalaemia?
Bradycardia
How do you manage hyperkalaemia?
Intravenous fluid therapy
Calcium gluconate
Glucose
Insulin
Why is calcium gluconate used in the management of hyperkalaemia?
Calcium gluconate does not directly lower serum potassium levels, however it is cardioprotective and can mitigate the immediate effects of hyperkalaemia on the heart, giving time for other treatments to lower the potassium more effectively
Why is glucose used in the management of hyperkalaemia?
When glucose is administered this stimulates the release of insulin which moves the glucose from the bloodstream into the cells. When glucose is moved into the cells, potassium and phosphate move with it which can help to correct the hyperkalaemia
Be aware you will have to monitor for hypoglycaemia
Why is insulin used in the management of hyperkalaemia?
When insulin is administered, this will move glucose, along with potassium and phosphate, into the cellswhich can help to correct the hyperkalaemia
Be aware you will have to monitor for hypoglycaemia
How can you relieve a urethral obstruction?
Catheterisation and retrograde hydropulsion
Surgical intervention
What are the benefits of a cystocentesis when attempting to relieve a urethral obstruction?
Cystocentesis can relieve the pressure on the bladder and thus make urinary catheterisation easier
What is the main risk of a cystocentesis in a patients with a urethral obstruction?
Uroabdomen
Which type of catheter can be placed as an indwelling catheter in cats?
KatKath catheter
Which type of catheter can be placed as an indwelling catheter in dogs?
Foley catheter
How do you carry out urinary catheterisation on a patient with a urethral obstruction?
- Sedate your patient of put them under general anaesthesia
- Assess the penis for any distal plugs or uroliths
- Aseptically clip and prep the perinuem
- Attempt to pass the urinary catheter aseptically to the obstruction and attempt retrograde hydropulsion
How do you carry out retrograde hydropulsion?
Flush the urinary catheter with sterile saline and lubricant in a pulsatile fashion in an attempt to push the obstruction from the urethra into the bladder. Use rectal palpation to assist in dislodging the obstruction. Make sure to not push the obstruction with the catheter as you risk iatrogenic urethral rupture
What should be done after retrograde hydropulsion?
Cystotomy to remove the obstruction from the bladder or medical dissolution with careful monitoring for reobstruction
What should be done post catheterisation?
- Take a urine sample via the catheter
- Once the urethra is patent, flush it thoroughly to ensure all debris removed and then advance the catheter into the bladder to flush and drain the bladder to remove any debris (blood clots etc)
- If you used an indwelling catheter attach a closed collection system to prevent the patient getting covered in urine in recovery
- Diagnostic imaging to ensure there are no other potential causes of obstruction
- For cats, sometimes it can be best to flush thoroughly, remove the catheter, put them on prazosin and send to cat home to reduce stress which can increase risk of re-obstruction