Urinary Tract Obstruction Flashcards
Causes of upper urinary tract causes?
Vaginouretral fistula d/t ligature of the ureter at spaying
Causes of intra urethral obstruction?
- tumour
- granulomatous inflammation
- prostatitis
- calculi
- foreign bodies
Extra urethral causes of obstruction?
- bladder/pelvis masses
- prostatic dz
- trauma (penile, pelvic, iatrogenic with perineal rupture repair, TPO)
Causes of bladder displacement
- retroflexion with perineal rupture
- displacement (abdo wall rupture/pelvic fractures)
- bladder torsion (often 2* to surgery not replacing)
Neurogenic causes of urine retention? LOOK UP
> LMN
- flaccid, over distended, easy to express, urine leakage
- sacral nerves affected (anywhere L5 caud jally)
- may be congenital (Manx cats)
- lumbosacral dz, cauda equina syndrome, vertebral fx
UMN
- more common
- firm, tense bladder
- lesions cranial to sacral nerve segmented
- intervertebral disk dz, tumours, luxations, fx
functional urethral obstruction (reflex dysynergia)
- more common dogs
- no relaxation of urethra
- hard to Tx
Which animals most commonly affected with urethral obstruction?
- males
- just caudal to os penis or any bend
- penile urethra in cats
General history Clinical signs of urethral obstruction
- dependant if obstruction complete or partial, acute or chronic, underlying cause
- inability or difficulty passing urine
- may be mistaken for constipation
- vulval/penile bleeding, Haematuria, V+
- collapse
PE findings with urethral obstruction
> full bladder
- beware rupture may feel like no bladder!
inability to pass catheter
- can give false results, just because you can get in doesn’t mean there is no blockage
poss mass on palp of pelvic region
- abdo pain, depression, unproductive straining and abdo distension
pathophysiology of obstruction
- changes similar regardless of underlying cause
- urethral -> bladder, kidney effects, 2* systemic effects
- upper tract less life threatening unless both kidneys affected
- can be lethal
How does obstructive uropathy affect kidney function
- ^ ureteral and tubular pressure -> bowmans space
- GFR falls
- v renal blood flow maintains low GFR
> ischaemia nephropathy may result in permenant nephron loss
Is azotaemia d/t urethral obstruction reversible?
Yes!! No matter how severe
Will a bladder be able to acutely distend to the rib cage?
No only chronic (will rupture if acute)
What Effects can obstruction have on bladder ?
> overdistension
- dependnt on rate of urine production, bladder capacity and compliance
- ^ intravesical pressure prevents ureteral emptying -> ureteral reflux
- ischaemia, oedema, haemorhage and mucosal sloughing may occour
Systemic effects of obstruction. Reversible?
> hypovolaemia, hypotension > biochem - azotaemia - acidaemia - hyperohosphataemia - hypocalceamia (phosphate ^ binds free ca) - hyperkalaemia > all reversible
How is hyperkalaemia seen on ECG?
- prolonged pR interval
- tall or peaked T waves
- brady cardia
- ventricular arrythmias
How do hyperkalaemic ECG traces differ in cats and dogs?
- cats more wide and bizarre almost like VPC but will not be tachycardic
What Is the most life threatening bit of obstruction?
Hyperkalaemia and hypovolaemia.
- CNS depression, vomiting, anorexia
How can hyperkalaemia be identified and managed?
- HR ( place IV catheter for IVFT
- before sedating etc. (Tx hypovolaemia don’t worry about rupture atm!)
- dilutes potassium
- calcium gluconate IV (stabilises myocardium to counteract potassium)
> cystocentesis to alleviate blockage - risk of leakage of urine into abdo, potential per acute septic peritonitis if have a UTI
- empty completely
- don’t put off GA
- prophylactic Abx
- allows stabilisation temporarily
- buys time to call in back up
- in cats risk of UTI very low
When shouldn you relieve the obstruction and empty the HR bladder?
Only when stable
- needs GA or sedation unless moribund
What should be remembered when passing a catheter in a male cat
- kink in the urethra
- pull penis caudally and dorsal lay to straighten
- stay suture or tissue forceps
- don’t push catheter, float the catheter into bladder
- lube, penile massage, flushing for clots, generally avoid stylet
- avoid Walpoles solution (v caustic for bladder and damage to urethral)
What needs to be done after unblocking
- save urine/plug for analysis (better if taken from cysto otherwise diluted with saline)
- bladder lovage with warm saline (until urine clear)
- when removing catheter express bladder and evaluate urine stream (urethral spasm can block)
- > if required place Indwelling catheter and closed collection system
- not always necessary, not well tolerated, may worsen urethral spasm
Should Abx be given prophylactically when they have a catheter in?
NO will not stop UTI but will make bacteria growing there resistant
What occours naturally following obstruction?
> post obstructive diuresis - match fluid ins and outs - (osmotic effect of retained solutes and damage to tubular feels) > hypokalaemia poss - check electrolytes - supplements IV FLUIDS - oral in food
What should be monitored for after obstruction
- UTIs
- Detrusor atony d/t excessive distension
- bladder outflow obstruction d/t bloodclot or sloughed mucosa
- stricture formation
What pharmacological agents may help post-obstruction
- Smooth muscle relaxants > a adrenergic blockers - phenoxybenzamine - prazosin > skeletal muslce relaxants - dantrolene - diazepam
What further investigation may need to be done post-obstruction clearance?
- not always done in first instance (may be better to r/o lesion)
- plain and contrast rads
- ultra sound and endoscopy
How can urinary tract obstruction be managed?
> surgery
- removing obstruction (urethrotomy, cystotomy)
- urinary diversion (cystotomy tube min 1w, can be permenant /scrotal/perineal urethrostomy / vaginitis-urethroplasty)
- re-establish urethral patency (end to end anastomoses in pelvic urethra for trauma or neoplasia)
minimally invasive techniques/flushing
- retrograde hydropulsion
medical or conservative management
cutting edge technologies
Is urethrotomy a good procedure?
No better to flush into bladder and do a cystotomy
Eg. of cutting edge techniques for obstructions
> urethral stenting - strictures and tumours > balloon dilation - stricture > endoluminal lithotripsy - calculi > endoluminal resection/ablation - tumours/polyps
Which is most common upper or lower obstruction?
??-
Egs of ureteral surgery
- ureteronephrectomy
- ureterotomy
- ureteral anastomosis
- ureteroneocystostomy (± psoas cystopexy, ± renal descensus)
- implants (subcut ureteral bypass system, ureteral stent, nephrostomy tube
Surgical options for management of upper urinary tract obstruction
- nephrotomy
- pyelolithotomy
