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Renal > Urinary obstruction in small animals > Flashcards

Urinary obstruction in small animals Flashcards

1
Q

Describe LMN bladder

A
  • flaccid
  • overdistended bladder
  • easy to express
  • urine leakage
  • congenital (manx cats)
  • cauda equina syndrome
  • lumbo sacral dz
  • vertebral fractures and dislocations
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2
Q

Describe UMN bladder

A
  • firm, tense bladder
  • difficult to express
  • lesions cranial to sacral nn segments
  • IVDD, tumours, luxations, fractures
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3
Q

CS - obstruction

A

DEPENDS ON: complete/partial, acute/chronic, underlying cause:

  • usually inability or difficult in passing urine
  • anuria, dysuria, stranguria, tenesmus
  • can be mistaken for constipation in cats
  • others: vulval/penile bleeding, haematuria, vomiting
  • mistaken for other dz if animal presents collapsed
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4
Q

PE findings - obstruction

A
  • full bladder (beware no bladder if ruptured)
  • inability to pass catheter (not reliable)
  • possible mass palpable on digital pelvic and urethral exam
  • other non-specific findings: abdominal pain, depression, unproductive straining, abdominal distension
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5
Q

Pathophysiology - obstruction

A
  • similar regardless of underlying cause
  • urethral obstruction serious effects on: bladder, kidneys, secondary changes affect systemically
  • upper urinary tract obstruction: less life threatening unless both kidneys involved
  • ultimate outcome death
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6
Q

Describe obstructive uropathy

A
  • increased ureteral and eventually tubular pressure
  • increased pressure in bowman’s space
  • GFR falls
  • reduction in renal BF d/t vasoactive hormones maintains low GFR–>ischaemic nephropathy may result in permanent nephron loss and kidney shrinkage
  • azotaemia d/t urethral obstruction may be reversible no matter how severe
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7
Q

Effects on bladder of overdistension

A
  • depends on bladder capacity and compliance and rate or urine production
  • increased intravesical pressure prevents ureteral emptying and may allow ureteral reflux
  • ischaemia, oedema, aemorrhage and mucosal sloughing (may cause another obstruction)
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8
Q

How might blocked animals present?

A

hypovolaemic (as haven’t been eating/drinking) and hypotension

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9
Q

Biochemical changes - obstruction

A
  • azotaemia
  • hyperglycaemia
  • acidaemia
  • hyperphosphataemia
  • hypocalcaemia
  • hyperkalaemia
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10
Q

Describe ECG changes associated with hyperkalaemia

A
  • prolonged PR interval
  • tall or peak T waves (t waves should normally be 1/4 amplitude of R wave)
  • bradycardia
  • sino-ventricular rhythm
  • ventricular arrhythmias
  • changes more characteristic in dogs than in cats
  • (in cats) don’t confuse with ventricular complexes if t waves merge with QRS
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11
Q

How quickly do blocked animals die?

A

usually within 72 hours

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12
Q

Emergency management of obstruction

A
  • Priority is to ID and correct life-threatening hyperkalaemia:
  • blood sample
  • IV catheter + IVFT
    = ECG if hyperkalaemic, or if unknonw {K+]
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13
Q

Tx - hyperkalaemia in obstructionfq

A
  • IVFT
  • calcium gluconate must be IV otherwise bad reaction: doesn’t alter [K+] but stabilises myocardium and improves arrhythmias so then safer to anaesthetise
  • relieve obstruction
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14
Q

Outline pros/cons decompressive cystocentesis

A

PROS: allows stabilisation d/t temporary ‘effective’ relief of obstruction, allows a new grad time, reduced hydrostatic pressure within bladder facilitates catheterisation, obstructed cats almost always have sterile urine so the risk of septic peritonitis v low
- CONS: avoid unless only option, risk of urine leaking into abdominal cavity –> septic peritonitis + death. If necessary: empty bladder completely, don’t put off GA, consider ABs

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15
Q

Method - relieving obstruction and emptying bladder

A
  • only when stable
  • sedation/GA unless moribund
  • urethral catheter: lubrication, penile massaage, flushing, care with cats, generally try and avoid catheter with a stylette, avoid walpole’s solution
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16
Q

What catheter to use

A
  • ensure long enough in cats
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17
Q

What to do after unblocking a cat?

A
  • save some urine or urine plug for analysis
  • bladder lavage: warm saline, flush until urine clear, when removing catheter express bladder and evaluate urine stream
  • if required, place indwelling catheter and closed closed collection system
18
Q

Should you give ABs when an animal has a catheter?

A

NO - only at removal and afterwards. Resistance WILL develop if there is a UTI present.

19
Q

Outline post-obstructive diruesis

A
  • keep ins with outs with IVFT
  • measure urine output
  • diuresis may be profound (d/t osmotic effect of retained solutes and damage to tubular cells)
20
Q

How is K+ affected after unblocking?

A
  • -> hypokalaemia
  • check electrolytes
  • supplement via IVFT
  • oral supplementation in food
21
Q

What to monitor for after unblocking

A
  • UTI
  • detrusor atony resulting from excessive distension
  • bladder outflow obstruction resulting from a blood clot or sloughed mucosa
  • stricture formation
  • struvite stones (females > males)
22
Q

Pharamcological therapy after obstruction

A
  • SMOOTH MUSCLE RELAXANTS: alpha-adrenergic blockers (phenoxybenzamine or prazosin)
  • SKELETAL MUSCLE RELAXANTS: dantrolene or diazepam
23
Q

Whaat further investigations are useful post-obstruction?

A
  • not always done with first occurrence of obstruction, especially cats
  • can r/o specific lesions
  • plain and contrast radiography mainstay of investigation
  • ultrasound and endoscopy also useful
24
Q

Outline management of urinary tract obstruction

A
  • different techniques
  • depends on: cause/dx, 1st episode/recurrent problem, owners wishes
  • options: sx, minimally invasive techniques / flushing, medical/conservative management, new cutting edge techniques/ technologies
25
Q

Describe retrograde hydropulsion

A
  • rarely fails
  • aim to flush urethral calculi back into bladder which are then removed via cystotomy/ laparoscopic assisted cystoscopy
  • preferred method of managing urethral calculi in male cats and dogs - always try first
  • easily combined with urethrography
  • 2 people
  • if unable to pass catheter may have to combine with cystocentesis
26
Q

Outline urinary diversion - CYSTOSTOMY

A

= tubes placed into blader across body wall

  • allow urine to drain and by pass urethra
  • indicated: to allow urine to drain if catheter cannot be placed, to protect urethra after sx/injury, as palliative tx for severe urethral dz
  • short term (1 week) or long term (years)
27
Q

What methods can be used to remove calculi/some other obstructing lesion?

A
  • cystotomy

- urethrotomy (avoid, better to flush stone into bladder then do a cystotomy)

28
Q

Outline urethrotomy

A
  • avoid!!
  • indicated ONLY when urethral calculi cannot be returned to bladder with hydropulsion
  • incidence of complications > cystotomy
  • usually performed pre-scrotally but can, if required, be performed at other sites
  • primary closure a good option provided excellent sz technique and suitable materials used
29
Q

What are the 2 neurogenic causes of urine retention?

A
  • LMN bladder

- UMN bladder

30
Q

Outline urinary diversion - URETHROSTOMY

A
  • permanent sx opening into urethra
  • used to bypass obstruction or to facilitate passage of stones/ sediment
  • salvage procedure
  • must be performed cr to obstruction
  • common sites: scrotal (dog), perineal (cat), prepubic (last resort)
31
Q

What are the sx options for managing upper urinary tract obstructio?

A
  • KIDNEY: nephrotomy or pyelolithotomy

- Other rarely used methods: urethral resection and anastomosis, vagino-urethroplasty

32
Q

Outline causes of urinary tract obstruction

A
  • urethral obstruction most common and immediately life-threatening, usually secondary to urolithiasis, may be secondary to other conditions (intra-urethral, mural or extra-urethral lesions), organ displacement
  • upper urinary tract obstruction less common. Azotaemia only if bilateral problem. Most likely calculi/ trauma
  • UTO may be associated with urinary tract disruption and urine leakage.
33
Q

Describe urinary tract obstruction

A
  • UPPER UT: kidneys, ureters

- LOWER UT: bladder, urethra

34
Q

Examples of intra-urethral causes of obstruction

A
  • calculi
  • tumours
  • inflammatory dz
  • FBs (rare)
35
Q

Examples: extra-urethral causes of obstruction

A
  • bladder masses
  • pelvic masses
  • prostatic dz
  • trauma (penile, pelvic, iatrogenic = perineal rupture repair or TPO = triple pelvic osteotomy)
  • others
36
Q

Causes: bladder displacement

A
  • retroflexion: perineal rupture
  • Displacement: abdominal wall ruptures/ pelvic fractures
  • bladder torsion
37
Q

What is functional urethral obstruction?

A

= aka = reflex dysynergia

  • rare
  • dogs > cats
  • animals dysuric, typically passing small spurts of urine and having a large residual volume
  • characteristics: no anatomic reason for obstruction, suspected functional dysynergia b/w detrusor contraction and urethral relaxation
  • objective proof rare and hard to get
  • medical management: to relax urethra, not always succesful
38
Q

List sx options for management of urethral obstruction

A
  • REMOVE CALCULI/ OTHER OBSTRUCTING LESION: cystotomy or urethrotomy
  • URINARY DIVERSION: cystostomy tube placement, permanent urethrostomy (scrotal urethrostomy in male dogs, perineal urethrostomy in male cats), vagino-urethroplasty
  • SURGERY TO RE-ESTABLISH URETHRAL PATENCY: end to end anastomosis (including approach to pelvis)
39
Q

List some cutting edge techniques and their indications

A
  • urethral stenting (strictures, tumours)
  • balloon dilations (strictures)
  • endoluminal lithotripsy (calculi)
  • endoluminal resection/ ablation (tumours, polyps)
40
Q

List different ureteral surgeries

A
  • ureteronephrectomy
  • ureterotomy
  • ureteral anastomosis
  • ureteroneocystostomy (+/- psoas cystopexy, +/- renal descensus)
  • implants (SC ureteral bypass system = SUB, ureteral stent, nephrostomy tube)

Renal (30 decks)

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