LA Urinary Tract Obstruction and Uroliths Flashcards
describe normal urine composition of herbivores, of horses specifically, and the effect of the diet
herbivores: alkaline pH (more likely to produce certain stones), clear, yellow, free of protein, blood, ketones, glucose
-all herbivores naturally low sodium diet
horses:
-mucus, calcium carbonate (so looks cloudy)
-exercise induced MICROSCOPIC hematuria and proteinuria is normal
effect of diet/predisposing factors to stone formation:
-grain (versus hay/roughage): higher phosphorous
-alfalfa (a legume, versus grass hay): higher calcium
-milk: low sodium, high K+, high water content, so nursing neonates are normally hyposthenuric
describe signs of urinary discomfort in large animals
- tail flagging/swishing
- parking out
- straining (arched back)
- vocalization (ruminants)
- urinating small amounts frequently
- colic
can be difficult to separate from GI pain! or from estrus behavior!
describe common sites of obstruction in bulls/steers, and in bucks/wethers
bulls/steers: distal to sigmoid flexure
buck/wethers: urethral process/vermiform appendage (very small and narrow = most common site of urolith obstruction!) or at sigmoid flexure
why do stones form?
- oversaturated urine: concentrated urine with crystals
- alkaline pH
- influenced by diet, dehydration, metabolism, and possible genetics
describe the prevalence of different types of stones
small ruminants:
-0-4 months: amorphous magnesium calcium phosphate (AMCP) and struvite (poorly radiopaque): likely to dissolve in acidic environment
-37 months: calcium carbonate (strongly radiopaque): will NOT dissolve
geography: in texas, AMCP and struvite more common, in GA: calcium carbonate more common
cattle:
-struvite (magnesium ammonium phosphate): FEED LOTS/GRAIN
-silica: grazing on grasslands of western north america
mineral analysis is the only way to know what stone you have!
describe the recipe for obstructive urolithiasis and interventions for each stage
MALE (wait until at least 4 months of age to castrate; will develop wider urethra)
+
tortuous long narrow urethra (see above wait to castrate)
+
alkaline urine (urine acidifers: ammonium chloride, bichlor, goal is urine pH <6.7)
+
dietary risk factors!! (avoid high grain/calcium diets; alfalfa/leguma <50% of total roughage)
+
poor water intake (clean, fresh, easily accessible water and salty treats to encourage drinking)
=
urinary canaliculi
how realistic is urine acidification in LA?
goal: target urine pH <6.7
-struvite forms at pH >7.2
-Ca phos forms at pH >6.5
how long and how often should use acidifiers?
-3 months or less
-compensatory re-alkalination with long term use
-pulse treatments (3 days on 4 days off) may be more beneficial
-avoid prolonged use of high doses!! can cause bone loss and anorexia!!! (taste terrible)
describe bio-chlor
- more palatable anionic salt
- 1-2 ounces daily: avoid overdose, 1 ounce per 110 lb body weight
- commercial and customizable feeds do exist
describe clinical signs of obstruction in ruminants
signalment: ANY AGE, MALE caprine, bovine, ovine, swine
nonspecific signs:
-pain
-depressed demeanor
-bruxism: teeth grinding
-bloat (free gas from not eating or drinking)
-off from the herd
-reduced feed intake
-small ruminants more likely to demonstrate signs of urinary tract pain: vocalization, posturing, tail flagging, straining
describe PE of obstruction in ruminants
- dehydration
- tachycardia
- turgid bladder on palpation
- digital rectal: pulsing of urethral
- dry urethra +/- crystals on preputial hairs
- reduced to absent rumen contractions +/- mild free gas bloat
describe diagnostics of obstruction in ruminants
clinicopathologic findings:
1. pre and post renal azotemia
- creatinine: magnitude varies with chronicity
-<24 hours: mild
->24 hours: severe - acid-base and electrolyte aberrations
<24 hours: none to mild
>24 hours: moderate to severe hyperkalemia, metabolic acidosis
diagnostic imaging:
1. transcutaneous ultrasound: ventral abdomen, urethra, bladder, and kidneys
-prognostic information; look at ALL
-if evidence of hydronephrosis, indicates chronicity and loss of normal nephrons
- radiographs:
-determine site of obstruction
-information about composition possible (radiopaque), but not always straightforward! so don’t rely on opacity!
describe medical stabilization of obstruction in ruminants
- pain meds/sedation
-use diazepam (relax), butorphenol (analgesia), acepromazine (relax, allow exteriorize penis) - IV catheter for IV fluids
-crystalloid fluid therapy: isotonic (mostly) or hypertonic (if super dehydrated, short term use only) - US guided cystocentesis:
-prevent bladder rupture
-relieve pain
-acidify? walpole’s solution (pH 4.5)
–helpful if younger animal (struvite or AMCP), might require multiple treatments for success - urethra process amputation:
-AVOID alpha-2 agonist: causes glucose diuresis (transient hyperglycemia, glucosuria); also ADH antagonism in collecting duct (causes diuresis)
-2% lidocaine
80% reobstruct within 36 hours!!
describe urachus
opening from bladder to outside world during foal-ness; can tear and be bad
what is the immediate life-threatening risk of obstruction (and to a more severe degree with uroabdomen)?
- hyperkalemia! causes dysrhythmias
-ECG alterations first: tented T waves, flattened P waves
-bradycardia (<60bpm in small ruminant or foal)
-tachyarhythmia
-DEATH
-CORRECT FIRST by draining fluid out of patient
- also need to address pain: abdominal distension/abdominal hypertension, inflammation from urine (chemical/sterile perotonitis)
describe principles of medical management for uroabdomen
signalment: foal or small ruminant (or valuable pet cow)
- IV catheter or IV fluid therapy
- IV fluid type: isotonic crystalloid: sodium chloride (0.9%), add calcium gluconate to stabilize cardiac membrane
- drain urine: somewhat slowly to prevent hypotension
-dump the potassium and creatinine out of the patient = very effective!!
-relieves some degree of pain and pressure on chest and vena cava - if hyperkalemia moderate to severe (at least 6.5-7 mEq/ml):
-dextrose 2.5-5% to IVF
-sodium bicarb
-rarely insulin! will be released by patient in response to dextrose so no need
goal before anesthesia: serum K+ <5.5 mmol/L
