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Flashcards in Urolithiasis (Specht) Deck (29):
1

urolith formation

  • Initiation requirements
    • supersaturation
    • precipitation
      • nucleation
  • Less saturation required for growth
    • direct growth slow process
    • aggregation can occur quickly

2

Stones probably result from

  • Nucleation + Growth + Aggregation

*aided by retention

3

Factors influencing precipitation

  • Solute conc
  • pH
  • other ions

 

  • proteins, inhibitors
  • surfaces present
  • bacteria

4

struvite, aka

magnesium ammonium phosphate

5

Most common stones we see in small animal

Calcium Oxalate (CaOx)

6

Stones caused typically due to inc solute conc

  • struvite, urate, cystine

7

Stones typically caused by lack of other ions, inhibitors

  • Calcium oxalate

8

Urolith composition

  • Mineral (crystalline component)
    • many kinds: struvite, CaOx, urate, etc
    • very imp for planning/prevention
  • Matrix (not very well understood)
    • proteins, GAGA, etc
    • Role is uncertain

9

Crystalluria

  • means supersaturated urine
    • risk of urolith formation
    • may help predict urolith type: diet changes, UTI's, etc
  • Crystals don't mean uroliths
  • Crystals don't equal pathology
  • Crystals may be artifactual due to cooling

10

When uroliths are imp

  • hematuria, pyuria
  • urgency, stranguria, pollakiuria
  • 2nd bact infections
  • obstruction
  • How important
    • in this patient....
    • at this time....

11

Diagnosis

  • Presence suspected based on
    • Hx & PE
    • UA
  • Diagnosed by imaging
    • rads
    • US
    • Contrast studies
      • for radioluscent stones
    • Endoscopy

12

Order of radioopaqueness (most to least)

  • CaOx
  • Struvites
  • Cystein
  • Urates
    • can sometimes still be seen on rads: big ones or with other minerals

13

Additional stone info

  • Number
  • Size
  • Location
  • Risk factors & concurrent dz

14

Definitive dx

  • mineral analysis
    • Minnesota: free, takes longer
    • UC Davis: faster

15

Treatment

 

  • urethral or bilateral ureteral obstruction is life-threatening
    • acidosis
    • hyperkalemia
  • initial tx: fluids
    • IV cath before U cath
  • If K+ and A-B status are safe then relieve obstruction
    • comatose cat: doesn't need sedation/anesthesia
    • if a cat can right itself: need sedation/anesthesia
    • palpate penis (cats) => might be able to express if in penis
    • rectal palpation in dogs
    • catheterization => retrograde
    • Don't forget lube
      • ​in cath and in flush solution
    • +/- decompressive cysto
  • Urinary diversion
  • Laser lithotripsy
  • surgery if necessary
    • ureteral stone removal
    • perineal urethrostomy

16

Medical therapy

Dissolution: struvite/urate

  • Some stones don't dissolve
    • we may not know what kind of stone is there
  • stones must be in bladder (bathed in urine)
  • risk of obstruction
    • small risk
  • Risk of worsening problem if we guess wrong
    • also small risk
  • Usually accomplished with diet 
    • reduce solute conc
    • modify urine pH
    • alter pop of other ions
  • Antibiotics if UTI present (complicated UTI)
    • until stone is out of body
  • +/- pH modulation
  • other meds (allopurinol in dalmations, methionine)
  • requires long-term plan for re-checks
    • compliance
    • follow-up

17

Catheter removal

  • may work for very small calculi
  • procedure
    • cath tip at trigone
    • patient help upright (bladder neck down)
    • bladder agitated and emptied
    • refill and repeat

*not a ton of presenting complaints that are conducive to this procedure

18

Urohydropropulsion

  • general anesthesia
  • catheter used to fill bladder w/saline then removed
  • patient held upright
  • agitate then let settle
  • express to achieve forceful stream
  • collect for exam
  • repeat until all stones collected
  • All stones less than urethral diameter
    • < 5 mm
  • better with smooth surface stones
  • be ready unobstruct or go to sx
    • rupture
    • obstruction
  • Useful for stone recurrance (small stones usually)

19

Cystoscopic retrieval

  • generalized anesthesia
  • utilization of
    • emtpty sheath
    • stone baskets
    • Ellik evacuator
  • can get a little bigger stone than voiding

20

Lithotripsy

  • Fragmentation of stone in vivo
  • less invasive than sx
    • not much cheaper tho
  • several methods

21

Lithotripsy

ESWL

  • shcok waves generated outside of body
  • precisely targeted
  • primarily useful when uroliths are fixed in location
    • nephroliths/ureterliths
    • can cause ureteral obstruction
  • limited availability

22

lithotripsy

laser

  • intracorporeal (laser) lithotripsy
  • holmium - YAG laser
  • quickly attenuates in fluid
  • proximity/contact to uroliths required
    • will damage bladder wall if comes in contact
  • most common for cystic calculi
  • at UF this is cheaper than sx
    • opposite from private practice
  • better for single stone or few small stones
  • better for female dogs
    • not feasible for small male dogs

23

Surgery

  • Most common
  • be aware of residual stones
  • invasive, but normally good outcome
    • laparascopic-assisted?
  • better for lower tract
    • more complications with upper tract
  • easy to leave stones behind

24

Preventative strategy

consider in....

  • consider in
    • recurrent urolithiasis
    • nephrolithiasis, ureterolithiasis
    • no identifiable underlying cause
    • underlying cause untreatable or uncontrolled

25

Non-specific prevention

  • inc H2O consumption
    • dec mineral conc
    • reduced possibility of super saturation
  • strategies
    • available fresh water
    • canned food
    • dry food with water
  • decrease urine retention/inc access to outdoors

26

Struvite stones

  • common in dogs
    • often assoc with UTI's
    • may respond to dissolution
  • In cats usually no assoc UTI
  • Usually do to super saturation events
    • liver dz - inc ammonia
    • change in mg
    • kidney dz - change in phosphate levels
  • Diet: lower mineral conc, pH modulation
    • slight risk of inc CaOx risk
  • pH modulation: acidifiers not usually necessary, may help assess other tx
  • Abx if UTI for as long as stones are present

27

Calcium Oxalates

  • can't be dissolved, complicated and poorly understood
  • 30-50% recurrence w/in 3 yrs
  • Risk factors
    • breed: schnauzers
    • inc Ca
    • obesity
    • primary hyperparathyroidism
    • chronic metabolic acidosis
  • Diet: something about moderate pH
    • Hills u/d; royal canin S/O
    • Hill's w/d
  • pH modulation
    • pushed to alkaline range
  • Hydrochlorathiazide
  • Potassium Citrate

28

Hydrochlorothiazide

  • dec Ca excretion
  • consider using if diet fails

29

Potassium Citrate

  • 2 potential actions
    • pH modulation
    • correction of hypocitraturia
  • Cosider when
    • diet, thiazides have failed
    • to achieve target pH