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Y4 SA - urinary & endocrine disease > Urolithiasis > Flashcards

Urolithiasis Flashcards

1
Q

Urolithiasis definition

A

= Calculi/uroliths (commonly known as stones) located anywhere along urinary tract

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2
Q

Causes of urolithiasis

A
  • struvite
  • calcium oxalate
  • urate
  • cysteine
  • calcium phosphate
  • xanthine
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3
Q

Where does urolithiasis normally occur in cats & dogs?

A
  • lower urinary tract, i.e. bladder & urethra
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4
Q

What are struvite uroliths made from?

A
  • Magnesium ammonium phosphate (MAP)
  • supersaturation of urine by Map -> struvite urolith
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5
Q

What are struvite uroliths usually associated with in dogs? What about in cats?

A
  • dogs: UTIs caused by urease producing bacteria
  • cats: 90% are sterile – in contrast to dogs (infection-induced seen predominantly in cats > 10 yrs)
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6
Q

Prevalence of struvite uroliths

A
  • Account for 40% of stones affecting lower urinary tract of dogs
    – Females > males – likely due to increased tendency of female dogs to develop UTIs
  • Account for 50% of stones affecting lower urinary tract of cats
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7
Q

Risk factors for struvite uroliths in dogs

A
  • Abnormal retention of urine; any condition predisposing to UTI – eg diabetes mellitus, hyperadrenocorticism
  • Susceptible breeds – Miniature schnauzer, Shih Tzu, Bichon
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8
Q

Risk factors for struvite uroliths in cats

A
  • Abnormal retention of urine
  • Formation of concentrated urine – moisture content of food, water intake
  • Urine-alkanising metabolites in diets
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9
Q

Calcium oxalate urolith prevalence

A
  • Account for approx. 40% of stones in dogs and cats
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10
Q

Calcium oxalate urolith causes

A

❑ Aetiology poorly understood
❑ Hypercalciuria*, hyperoxaluria, hypocitraturia
❑ Hypercalciuria – increased intestinal reabsorption of calcium or reduced renal tubular reabsorption
- hypercalcaemia – renal tubular reabsorption mechanisms overwhelmed

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11
Q

Is recurrence of calcium oxalate uroliths common?

A
  • yes
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12
Q

Calcium oxalate risk factors

A

❑ Acidifying diets
❑ Oral calcium supplements given outside of mealtimes
❑ Excessive dietary protein
❑ Formation of concentrated urine

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13
Q

What are urate uroliths made of?

A
  • uric acid, sodium urate or ammonium urate
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14
Q

Cause of urate uroliths

A
  • Impaired conversion of uric acid to allantoin
    -> increased concentration of uric acid in serum andurine
  • Often associated with PSS – due to impaired hepatic metabolism of uric acid and ammonia
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15
Q

Breed predisposition for urate uroliths

A
  • Dalmations and Black Russian terriers
  • Associated with breeds predisposed to PSS eg Yorkshire Terriers
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16
Q

Urate urolith prevalence

A
  • 5-8% of uroliths in dogs and cats
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17
Q

Urate urolith risk factors

A

❑ High Purine intake (glandular meat)
❑ Persistent aciduria in a predisposed animal

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18
Q

Cause of cysteine uroliths

A

❑ Cystinuria – inborn error of metabolism caused by defective tubular resorption of cysteine and other amino acids
❑ Not all cystinuric dogs develop cysteine uroliths – cystinuria is a predisposing factor

19
Q

Cysteine urolith risk factors

A

❑ Genetic predisposition to cystinuria
❑ Acidic, concentrated urine
❑ Urine retention

20
Q

Cysteine urolith signalment & breed predispositions

A

❑ Breeds with genetic mutations include Newfoundlands, Labradors, Australian cattle dogs, mastiffs and bulldogs
❑ Predominantly intact male dogs affected

21
Q

Calcium phosphate urolith prevalence

A

❑ Pure Calcium Phosphate uroliths - less than 1% of all uroliths in dogs and cats

22
Q

What are calcium phosphate uroliths often a minor component of?

A
  • struvite and calcium oxalate uroliths
23
Q

Xanthine urolith causes

A

❑ Impaired Xanthine oxidase activity leads to hyperxanthinaemia and xanthinuria
❑ Familial or congenital defect e.g. CKCS
❑ Allopurinol therapy can lead to acquired xanthinuria

24
Q

Xanthine urolith risk factors

A

❑ Genetic predisposition
❑ Acid urine, highly concentrated urine
❑ Urine retention
❑ Allopurinol treatment

25
Q

Urolithiasis: clinical signs

A

❑Lower urinary tract signs – dysuria, haematuria, pollakiuria
❑+/- signs of urinary obstruction
❑Urate – signs of PSS

26
Q

Urolithiasis: diagnosis

A
  • Urinalysis
  • Imaging
  • Ultrasound
27
Q

Urinalysis for diagnosis

A

❑ Not as helpful as you might think
❑ pH is useful – partly clue to urolith type, but also for monitoring treatment/dietary management
❑ Need to rule out UTI – and if present, must treat especially if struvite uroliths
❑ Crystals can be misleading- once a urolith has formed, minerals are more likely to be deposited on the surface of the urolith than to form new crystals, so crystals are often absent when uroliths present
❑ If crystals present, may not represent urolith composition – eg struvite crystalluria often seen in dogs with calcium oxalate uroliths as urine is therapeutically alkalinised.

28
Q

Radiography for diagnosis

A
  • Radiopaque uroliths: Calcium Oxalate, Struvite, Calcium phosphate
  • Radiolucent uroliths: Xanthine
  • Variable: Urate, Cysteine
  • Struvite: usually round/faceted, appear smooth
  • Calcium Oxalate: more irregular
29
Q

Ultrasound for diagnosis

A

❑ Acoustic shadowing
❑ Remember gravity when
deciding if mass or urolith
❑ Can be done conscious
❑ Will pick up radiolucent uroliths

30
Q

When can you do urolith analysis?

A
  • either post cystotomy, or if small uroliths are passed
31
Q

Non-specific medical tx

A

❑ Analgesia – usually NSAID
❑ Antibiotic if concurrent UTI (e.g. with Struvite) – culture and sensitivity as will usually need
prolonged course if uroliths present
❑ Lithotripsy – only one place in the UK currently, owners may ask about it

32
Q

Urate specific tx

A

❑ Allopurinol – Xanthine Oxidase inhibitor – for dissolution – takes at least 4-6 weeks, sometimes required long term
❑ Not effective if PSS – need to manage the shunt

33
Q

Diets for dissolution (tx) (for each urolith)

A
  • Calcium Oxalate: Not amenable to dissolution (dietary management is for prevention of recurrence)
  • Struvite: Prescription struvite dissolution diet (acidifying)
  • Urate: Low-purine, alkalinising diet (contraindicated if pregnant/lactating)
  • Cysteine: Alkanising, lower methionine protein content
  • Calcium phosphate: not amenable to dissolution
  • Xanthine: low purine, alkalinising
34
Q

Which uroliths would you treat surgically?

A
  • Calcium Oxalate
  • Calcium phosphate
  • larger Struvite uroliths
35
Q

Surgical tx

A

❑ Cystotomy, urethrotomy
❑ If blocked – try and push urolith(s) back into bladder by retrograde urohydropulsion
❑ Cystotomy – rarely an emergency – remember lower ASA risk if planned not emergency, can ensure adequate personnel available, do in morning so time to recover and usually home
same day

36
Q

Surgical tx - post op warnings to O

A
  • warn owner of likely haematuria, need to monitor urine output, watch for dysuria
37
Q

Surgical tx - peri- & post-op analgesia

A
  • opioid
  • NSAID
38
Q

What else do you need to do post-surgery for struvite crystals?

A
  • take urine sample for C & S (unless done recently)
39
Q

Prevention of calcium oxalate uroliths

A
  • High moisture alkalinising diet – but monitor for Struvite crystalluria
  • Monitor – monthly urinalysis, aim for SG < 1.020 (dogs) & < 1.030 (cats) and pH >6.5
  • Correct any hypercalcaemia
40
Q

Prevention of struvite uroliths

A
  • High moisture acidifying diet – but care re CaOx crystalluria
  • Monitor urine pH & SG (as for CaOx but want pH < 7
  • Ensure UTI fully resolved – repeat C & S at end of antibiotic course
41
Q

Prevention of urate uroliths

A
  • High moisture alkalinising diet
  • Some dogs require long term Allopurinol
42
Q

Prevention of cysteine uroliths

A
  • High moisture alkalinising diet
  • Dogs – consider castration, will reduce recurrence if have sex-linked genetic predisposition
43
Q

Prevention of calcium phosphate uroliths

A
  • High moisture diet; senior diets may be useful due to lower protein
44
Q

Prevention of xanthine uroliths

A
  • High moisture alkalinising diet

Y4 SA - urinary & endocrine disease (17 decks)

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