Urolithiasis Parts 1 and 2 Flashcards
describe evaluation of crystalluria
urine should be evaluated in light of
- pH of urine
- sample collection technique
- time between collection and analysis
-if refrigerate, ALL urine will form crystals!!! need to evaluate in original conditions (like when in bladder)
it is possible to collect a “crystal pellet” for analysis
-if lots of crystals, can centrifuge, siphon off urine, and send crystal pellet for analysis
describe pH or urine as relates to crystal formation
MOST form when urine is acidic!!
5-7: calcium phosphate, purines, calcium oxalate, cystine, silica
7-8: sterile struvite
8-9: infection-induced struvite, calcium apatite
review the types of crystals
see lecture pics and path lecture if need
ammonium URATE (not biurate, technically): dalmatians and english bulldogs and jack russell terriers prone
-also with portosystemic shunt
cystine: always 6-sided and sometimes stick together (risk factor)
amorphous: we don’t know what they are
cholesterol: not common in dogs and cats, weird rectangle thingies
lipid: common in horses and fat cats
describe struvite stones (5)
- most radiodense (as dense as bone)
- fairly large size
- variable shapes
- smooth contour
- often many stones
descrieb calcium oxalate stones (4)
- radiodense (not as much as struvite)
- usually small and round
- often not more than a dozen stones
- irregular surface
describe cystine stones (4)
- marginally radiodense
- usually small and round
- often smooth contour
- usually less than a dozen or so
describe urate stones (4)
- usually radiolucent
- usually small and round
- smooth
- multiple stones
describe the stones in terms of radiodensity
Piss On Cornell University
Phosphate or Struvite
Oxalate
Cystine
Urate
describe biochemistry of urolithiasis (4)
- hyperadrenocorticism
- hypercalcemia
- increased UTI
- liver disease
what are the most common bladder stones in dogs? cats?
dogs: struvite or calcium oxalate
cats: same
describe catheter assisted retrieval of stones
flush fluid in via catheter, someone bounces the bladder, suck up the small stones
good for small stones or sandy/gritty stones
describe voiding urohydropulsion (4)
- goals are relaxation, compliance, analgesia
-need to take away conscious control - pass catheter to distend bladder, hold animal upright, shake them, then gentle pressure squeeze bladder until exceed micturition reflex
- re-image to see if got all stones
- dogs do very well with this technique, but cat bladders are very unforgiving
-usually develop hematuria, hospitalize overnight
-works for any stones not wider than smallest diameter of urethra
describe cystoscopy (3)
- rigid in females, or flexible or semi-rigid also exist for dudes
- pass graspers and grab stone once visualize
- or can pass a laser fiber through and break up stone inside if too big to pull out
describe percutaneous cystotomy lithotomy (2)
- make a small incision in abdomen and insert a scope
- lots of magnification = can see/remove all the little stones and then check surface of bladder for damage once done
describe struvite urolithiasis
signalment:
infection: females, neonates, older (more common in dogs)
sterile: young adult cats
blood work: usually normal, or evidence of predisposing cause
urinalysis:
infection: alkaline
sterile: neutral
struvite crystals
+/- UTI
radiography: multiple, dense, wafer to pyramidal, smooth
can dissolve medically!!
-if correcting surgically and have a negative urine culture, consider bladder biopsy and culturing the stone as well
how does a struvite infection begin?
- lots of urea, metabolized by bacterial urease to ammonia
-most common urease-producing bacteria: STAPHYLOCOCCUS!!! (gram + cocci), others too but mostly staph - ammonia combines with hydrogen and forms ammonium (cation) and phosphate and magnesium
-magnesium ammonium phosphate (struvite)
-struvite crystals form when urine pH 7.0-7.4 - excess CO2 from ammonia conversion forms carbonate appatite
- ammonium can combine with uric acid to form ammonium urate
- alkaline ammonium damages mucosa
describe risk factors for sterile struvite formation
- environment: hot climate
- patient:
-chartreaux, DSH, foreign SH, himalayan, oriental SH, ragdoll
-females or MC
-younger
-obese
-indoor only
-less physical activity
diet:
-highest Mg, P, Ca, Cl
-moderate protein
-alkalinizing
-lower water intake
describe treatment of infection induced struvite
- surgery
- MIPS: minimally invasive procedures
- medical dissolution:
conventional:
-feed a modified diet (low Mg, phos, protein, acidifying, diuresing
-administer antimicrobial
-Abx for an average of 8 weeks: urease producing microbes (staphylococcus); bacteria are trapped in the matrix of the crystal, so give antibiotics during crystal dissolution (bacteria released as crystal dissolves)
-ideally a potentiated beta lactam (clavamox)
alternative:
-don’t change diet (changing diet won’t prevent infection!)
-give acidifier (d,I-methionine)
-administer antimicrobial for an average of 8 weeks
describe prevention of struvites
infection:
-prevent/treat UTI
-no special diet
sterile:
-modified diets!
-combo struvite/oxalate
-lower minerals
-slightly acidic to neutral pH
-diuresing
describe urate urolithiasis
signalment:
-liver disease: young, small breeds, males and females equally
-without liver disease: young adult, males>females, dalmatians, english bulldog, black russell terrier
bloodwork:
-liver disease
-or normal if no liver disease
urinalysis:
-acidic
-urate crystals
radiography:
-numerous lucent round smooth ammonium urate crystals
describe urate formation
- dietary purines and endogenous purines all enter the purine pool which are ultimately converted to uric acid and then to allantoin by nonhuman primates
- with liver disease, or animals with the transporter ALC2A9 gene, block uricase, so stuck with uric acid
-all classic dalmatians are classic high uric acid excreters (only 20% form stones tho)
-but made a freak second dalmatian that’s a low uric acid excreter (by breeding with an irish setter); more likely to form other types of stones
-heterozygotes are carriers, homozygous recessive mutation = high excreter
describe urate crystal dissolution
- undersaturate urine (get rid of uric acid and ammonia in urine)
-low protein
-alkaline
-increase urine volume (push out) - xanthine oxidase inhibitors/allopurinol:
-block conversion of xanthine to uric acid
-side effects: xanthine formation (yellow) - works in about 1/3 cases, some get bigger bc form xanthine
-success rate is about 50/50
-if going to dissolve, will dissolve within a month
what is the difference with urate dissolution in cats?
allopurinol can’t be used in cats! more likely to require surgical intervention
describe urate prevention in dogs versus cats
dogs:
-diet: low protein, alkaline, increase urine volume
-allopurinol
cats:
diet: low protein/purine, alkaline, increase urine volume
