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Renal > Urolithiasis in small animals > Flashcards

Urolithiasis in small animals Flashcards

1
Q

Size - uroliths

A

macroscopic (crystals = microscopic)

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2
Q

T/F: you can have crystals without uroliths and uroliths without crystals

A

True

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3
Q

Are crystals always representative of urolith type?

A

May be but not always

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4
Q

How are uroliths described?

A
  • mineral component

- location

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5
Q

How are uroliths formed?

A
  • crystlas form when urine is supersaturated

- concentration of solute required to start the process (nucleation) generally higher than that needed for growth

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6
Q

PE - nephroliths and ureteroliths

A
  • often normal

- hydronephrsis/ irregular kidneys

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7
Q

CS - cystoliths

A
  • dysuria
  • pollakiuria
  • haematuria
  • inappropriate urination
  • generally not palpation
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8
Q

CS - urethroliths

A
  • abdominal discomfort
  • poor/no urine stream
  • licking genitals
  • obstruction and post-renal azotaemia
  • enlarged painful bladder, urethroliths may be palpable per rectum or at base of penis
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9
Q

Dx - urolithiasis

A
  • compatible hx and CS
  • plain radiographs (radiodence uroliths if sufficienctly large)
  • contrast radiograph (excretory urogram for nephroliths, reteroliths, double contrast - bladder, retrograde - urethra)
  • ultrasound
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10
Q

How can you predict urolith type?

A
  • signalment
  • radiopaque/lucent
  • urine pH
  • hx of a particular stone type
  • UTI associated with struvite
  • disease associations
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11
Q

Urinalysis - analysis

A
  • qualitative analysis not reliable

- quantitative analysis required (reputable lab) = xray diffraction (detailed analysis of mineral composition)

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12
Q

General tx considerations - renal and ureteral stone

A
  • sx removal (traumatic)
  • urinary bypass
  • lithotripsy (non-UK)
  • dietary dissolution (must be non-obstructed, often CaCO3 which isn’t amenable to dissolution)
  • benign neglect
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13
Q

General tx considerations - bladder stone

A
  • medical dissolution
  • voiding urohydropulsion (VUH)
  • sx (cystotomy)
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14
Q

General tx considerations - urethral stone

A
  • retrograde flush into bladder

- sx (urethrotomy, urethrostomy)

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15
Q

Indications - medical management

A
  • prior to sx if appropriate
  • no obstruction
  • no CI to dietary therapy
  • urolith composition amenable to dissolution
  • struvite, cystine an durate
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16
Q

Principles - medical management of uroliths

A
  • decreased concentration in urine by increasing water intake
  • decrease quantity of calculogenic cyrstalloids by diet r drugs
  • increase solubility of slats by changing urine pH by diet
  • tx predisposing cause
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17
Q

Outline urohydropulsion

A
  • fill bladder with saline
  • position so urethra vertical
  • agitate
  • allow stones to settle
  • initiate voiding
  • conitnue pressure to keep brisk urine flow
  • 3 days ABs
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18
Q

Other names - struvite crystals

A
  • magnesium ammonium phosphate

- triple phosphate

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19
Q

Outline struvite crystals

A
  • many breeds
  • most dogs have concurrent UTI
  • most female
  • urease producing bacteria (Staph, Proteus)
  • cleave urea –> ammonium + bicarbonate
  • alkaline urine pH
  • sterile in cats
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20
Q

Struvite - tx

A
  • treat UTI for 3-4 weeks after radiographic resolution
  • reduce urinary Mg, ammonium, phosphate
  • maintain pH
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21
Q

Struvite prevention

A
  • hill’s and royal canin preventative diets
  • long term preventative tx not recommended for dogs unless sterile stones
  • monitor for UTI recurrence
  • diets designed to prevent struvite recurrence may lead to calcium oxalate stone formation
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22
Q

Signalment - calcium oxalate

A
  • increased incidence, esp cats (inappropriate acidifying diet to prevent struvite but promotes oxalate)
  • terriers, poodles, schnauzers, burmese, himalayan, persian
  • older animals
  • upper urinary tract
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23
Q

Calcium oxalate - tx

A
  • sx
  • urohydropulsion
  • medical dissolution not possible
  • ignore
  • 60% recurrence within 3 years
24
Q

Prevention - calcium oxalate

A
  • increase water intake (least controversial idea)
  • sodium supplementation? (salt –> drinks more. induces diuresis)
  • neutralising urine pH won’t have a big effect (calcium oxalate solubility not pH dependent, acidiying diets promote calcium excretion)
25
Q

What is laser lithotripsy?

A
  • guided by cystoscopy
  • fragments removed by VUH
  • BUT energy absorbed by water (effects only within 1-2mm fibre tip)
26
Q

Outline ammonium urate stones

A
  • 8% canine stones
  • DALMATIONS: reduced conversion of uric acid to allantoin, defective transport of uric acid into hepatocytes andout of urine
  • Hepatic dysfunction: PSS, increased excretion of ammonia and urea.
  • bulldogs and others
27
Q

Ammonium urate - tx

A
  • tx underlying liver disease and PSS
  • otherwise dissolution
  • tx any UTI
  • reduce purine, neutral to alkalinepH (Hills u/d)
  • allopurinol (competitively inhibits xanthine oxidase, reducing uric acid this can result in xanthine stones if protein not restricted)
28
Q

Describe cystine stones

A
  • 3% canine stones (breeds)
  • renal tubular defect resulting in excess urine cystine which is poorly soluble
  • typically middle aged, despite being a congenital problem
  • radiolucent
  • medical dissolution effective but v expensive
  • cystine excretion decreased by castration
29
Q

Describe calcium phosphate stones

A
  • associated with primary hyperPTH
  • also mixed urolith
  • inerlaistion of blood clot
30
Q

Describe calcium carbonate stones

A
  • commonest in horses and rabbits

- high {Ca2+] in ruine

31
Q

Describe silica stones

A
  • GSDs predisposed
  • rare
  • associated with poor diets
32
Q

Sx management of urolithiasis - indications

A
  • UT obstruction
  • unknown or unpredictable urolith composition
  • failed medical tx
  • presence of other urinary tract abnormalities
  • immature dogs (d/t specific dietary requirements)
  • owner preference
  • cost
33
Q

Sx options

A
  • open viscus and remove calculi (nephrotomy, pyelotomy, ureterotomy, cystotomy, urethrotomy)
  • provide urine diversion (create an artificial opening, usually permanent)
34
Q

General sx considerations

A
  • stabilise hyperkalaemic and severely azotaemic animals pre-sx
  • ensure # and location of calculi are known immediately before sx
  • place indwelling urinary catheter (with extension set) and empty bladder
  • check all calculi / fragments of calculi are removed at end of sx
  • submit calculi for quantitative analysis
35
Q

Method - cystotomy

A
  • place urinary catheter connected to an extension set prior to sx
  • caudal midline ventral celiotomy, care entering peritoneal lcavity
  • locate bladder and empty if necessary, place stay suture - prolene, in apex
  • pack of abdominal cavity
  • ventral midline cystotomy and use further stay sutures to aid manipulaiton
  • remove obvious calculi (forceps)
  • save for quantitative analysis and culture
  • flush urethra with sterile saline - non-sterile assistant to do until ALL calculi removed
  • close bladder using syntehtic absorbable material e.g. poliglecaprone = monocryl, single or double layer, continuous or interrupted, appositional or inverting, try and avoid placing stay suture in bladder lumen
36
Q

What are end of cystotomy considerations?

A
  • are all calculi removed
  • consider xray post-op
  • generally indwelling catheter not used
  • usual to keep on IVFT for 12-24 hours
  • need to be allowed to urinate frequently
  • analgesia
  • medical management (dependent on calculus)
37
Q

Risks/complications - cystotomy

A
  • not removing all calculi -> CS recur
  • dehiscence of bladder –> uroperitoneum
  • blood clot –> outflow obstruction
  • CS: cystitis
38
Q

Radiographic density of calcium oxalate monohydrate (COM)/ dihydrate (COD)

A

moderately to markedly radiopaue

39
Q

Surface characteristics - COM/COD

A

sharp projections, mulberry shaped or smooth round uroliths

- COD may be jackstone shaped

40
Q

Urine pH - COM/COD

A

acidic to neutral

41
Q

Crystalluria with COM/COD

A
  • COM crystals (dumbbell or picket fence shapes)

- COD (square envelopes)

42
Q

UTI with COM/COD

A

None or secondary UTI with common uropathogens

43
Q

Breeds - COM/COD

A
  • miniature schnauzer
  • lhasa apso
  • YT
  • bichon firse
  • pomeranian
  • shih tzu
  • birmese, himalayan, persian
44
Q

Uroliths of COM/COD

A

often multiple small uroliths in bladder. multiple nephrolights is present.
- males > females (dogs and cats)

45
Q

Radiographic density - struvite

A

mod to markedly radiopaque

- larger uroliths more radiopaque

46
Q

Surface characteristics - struvite

A

SINGLE: smooth or speculated, may assume shape of bladder
MULTIPLE: smooth surfaces where uroliths contact each other, often pyramidial

47
Q

Urine pH - struvite

A

alkaline

48
Q

Crystalluria with struvite

A

struvite or ‘triple phosphate’ crystals (coffin lid appearance)

49
Q

UTI with struvite

A

urease producing organisms (staph,proteus, mycoplasma).

- sterile struvite uroliths in cocker spaniels and cats

50
Q

Breeds - struvite

A
  • miniature schnauzer
  • shih tzu
  • bichon firse
  • miniature poodle
  • cocker spaniel
  • lhasa apso
51
Q

Uroliths > what size are likely to be struvite?

A

> 1cm

52
Q

Describe urate/xanthine stoes

A
  • radiolucent to faintly radioopaque
  • multiple smooth uroliths
  • acidic urine
  • ammonium urate crystals (yellow-brown ‘thornapple or spherical’) or amoprhous urate crystals
  • no UTI or secondary UTI with common uropathogens. Rarely urease producing organisms
  • Dalmation, english bulldog,miniature schnauzer, shih tzu, YT
  • PSS or other liver dysfunction
  • yellow-green urolith colour,
  • DOGS: Males> females
  • CATS: equal b/w sexes
53
Q

Describe cystine stones

A
  • radiolucent to moderately radioopaque
  • multiple smooth round uroliths in bladde/urethra
  • nephroliths staghorn shape
  • acidic urine
  • cystine crystalluria always abnormal
  • no UTI or seconday UTI with common uropathogens
  • mastiff, australian cattle dog, english bulldog, SBT, newfoundland, dachshund
  • positive urine-cyanide nitroprusside test
  • metabolic screening of urine available
  • DOGS: males»»females
54
Q

Describe calcium phosphate crystals

A
  • moderately to markedly radioopaque
  • SURFACE: hydroxyapatite (multiple small uroliths with variable shape) or brushite (multiple smooth round or pyramidal uroliths)
  • alkaline to neutralurine pH for hydroxyapaptite, acidic for brushite
  • crystalluria: amorphous phosphates or calcium phosphate crystals (thin prisms)
  • no UTI or secondary UTI with common uropathogens
  • YT, miniature schnauzer, bichon friese, shih tzu, springer spaniel, pomeranian, miniature poodle, cocker spaniel
  • hypercalcaemia predisposes this
55
Q

Describe silica crystals

A
  • moderately radioopaque
  • classic jackstone appearance
  • acidic to neutral urine pH
  • no crystalluria
  • no UTI or secondary UTI with common uropathogens
  • GSD, OESH, labrador retriever
  • males&raquo_space; females

Renal (30 decks)

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