Reptile Urology Flashcards
list the common clinical signs of renal disease in reptiles and birds
- unlikely to show clinical signs until 2/3 function lost!
- owners report:
-decreased activity, depression, weakness
-inconsistent or decreased appetite
-regurgitation
-dysecdysis: abnormal shedding
-abnormal urine/feces
-increased bathing - RARELY REPORT: PU/PD, anuria
describe the history and physical exam for renal disease
- always ask about husbandry!
-humidity and water provision, management failures (water/sprinker malfunction or thermostat failure), vitamin supplementation (hypervitaminosis D3 and renal mineralization), home treatments (esp aminoglycosides causing nephrotox - physical exam
-weight, BCS (acute vs. chronic)
-neuro function and mentation (hyperuricemia can cause encephalopathy)
-integument: mucosal ulcers, skin ulcers or lost digits, abnormal shedding
-edema: peripheral (around limbs)
-ascites: Na+ retention, fluid overload
-joints: articular gout, (pseudogout Ca2+ salts), visceral gout (in tissues); occurs in diseased tissues first (kidneys); URIC ACID MEASUREMENT!!
-kidney palpation: renal enlargement; cutaneous or per cloaca
describe clinical pathology of renal disease
- blood collection should precede any treatment! as soon as treat can mask changes
- CBC: suboptimal temp may mask response of reptiles (if too cold, cannot mount immune response)
-EDTA can lyse some reptile RBCs (chelonians), but preferred for lizards and snakes
-need to perform manually (most send off), in practice at least do PCV/TS (serial samples help determine how fluid therapy is going) - biochem:
-UA/BUN/NH4: increase in acute, decrease in chronic (anorexia for several months)
–BUN (land chelonians; semi-aquatics), NH4 (aquatics, crocodilians, alligators), UA/uric acid (lizards and snakes)
-decreased/inverted Ca:P ratio in many lizards
-K+ and Na+ increase in acute, decrease in chronic cases
-increased AST, CPK, LDH: wide tissue distribution; so elevation could be due to something else (cachexia)
-increased GGT with tubular disease
-decreased albumin (protein electrophoresis only to be accurate)
-decreased 1,25-vitamin D3 (LCMS only): secondary renal hyperparathyroidism common in older reptiles (we measure 25 only, skipping the renal part, oops)
describe urinalysis of reptiles
urine collection: voided cystocentesis, catheterization (hard bc so many holes in cloaca)
-bladder urine in reptiles is rarely sterile!!
-UA:
–gross observation: volume (production), color, turbidity, specific gravity not very helpful (isosthenuric always, reptiles cannot concentrate urine above plasma!!!)
–dip stick: pH, blood, protein, specific gravity, ketones, (uro)bilirubin, glucose
–desert tortoises naturally produce ketones so that’s not helpful
-urine sediment eval: cytospin (1000-1500rpm for 5 min); unstained and stained slides
–casts are usefully abnormal
–uric acid crystals are normal!
–expect to see some bacteria bc exists through cloaca, if heavy load, then more concerned
–protozoa: hexamita are pathogenic until proven otherwise
describe diagnostic imaging for renal disease in reptiles
radiographs:
extension of iguana kidneys cranial to pelvic margin
see a lump of 55-65% snout to vent = mass/enlarged kidneys
can’t normally see kidneys in snakes bc low visceral fat but renal gout looks speckly
chelonians: very tough to see through shell but will see uroliths very clearly on radiography
ultrasound: very helpful!
-hyperechoic spots throughout kidney= uric acid deposition and complex with other minerals
describe GFR measurement in reptiles
- maintain reptile within species specific preferred optimal temperature zone (POTZ)
- ensure reptile is well-hydrated and fasted for 24hr
- measure accurate body weight
- administer 75mb/kg iohexol at time 0
-collect 0.3-0.4ml of blood at 4hr, 8hr, and 24hr - centrifuge, separate, and freeze plasma
-don’t need large sample, can do with any reptile >300grams - submit 3 samples on ice
RESULTS: GFR quantifies renal function and prognostic value
-normal: 10-20 ml/kg/hr with species variation
-GFR can be normal in the face of elevated uric acid if high protein diet to herbivore!!
describe definitive diagnosis of renal disease
- kidney disease is not a diagnosis!
-renal cysts, intersititial nephritis, glomerulonephritis, pyelonephritis, etc.
-many things can cause renal disease! - definitive diagnosis:
-demonstration of the host pathologic response
–histopath > cytology > paired rising titers
-demonstration of etiologic agent: microbiology, parasitology, toxicology
describe renal biopsy
indications:
1. unexplained renal failure
2. persistent electrolyte imbalance, hyperuricemia/hyperuremia
3. severe proteinuria, hematuria
4. renomegaly or masses (primary or secondary)
endoscopic renal biopsy:
-direct visualization
-typically two biopsies collected if possible
–histopath, microbiology
-minor hemorrhage, no significant complications
describe key therapeutic approaches/general approach to treatment
- do NOT start treatments that will invalidate diagnostics:
-no fluids before blood collection
-no antibiotics before sampling for microbiology (not always possible but is the goal)
-do NOT give NSAIDs - initial triage:
-ensure normothermic!!! if not, nothing you do will have any effect
-blood collection (CBC and biochem)
-start fluid therapy - then fluids, allopurinol, dietary modification (see more later)
describe prerenal, renal, postrenal causes of acute kidney injury/disease (etiology and pathogenesis)
pre-renal: normal kidneys
1. hypotension, total volume depletion (dehydration, hemorrhage)
- NSAIDs: vasodilatory PGs secreted by glomeruli
renal:
1. prolonged ischemia, acute tubular necrosis: rhabdomyolysis, drugs (aminogly, amphot B; aminoglycosides; if have to give administer with fluids!), contrast agent
- acute interstitial nephritis: infection, adverse drug effects (sulfa, amoxi, PPI)
post-renal:
1. blockage or obstruction: nephron, ureter, duodenum
-if in bladder doesn’t normally cause obstruction in reptiles! unless stick in pelvic inlet
- uric acid/gout (renolith, ureterolith, cystic calculus)
- egg, fecolith or calculus in cloaca (ureteral, not urethral blockage)
describe fluid therapy
- characterize electrolyte imbalances
-if hyperkalemia and metabolic acidosis avoid K+/lactate in fluids (5% dex 0.2% saline, sodium bicarb)
-prefer LRS
-but difficult to repeat samples
-if hypokalemia: use K+ supplement, beware of fluid overload (weigh every day, monitor PCV if can)
- route of admin:
-IV, IO>ICe, SQ>PO
-critical/shock: 5ml/kg 1st hour then 3ml/kg 1-6 hrs
-rehydration: 1.25-2 ml/kg/hr
-maintenance: 0.5-0.75 ml/kg.hr
-anuric/oliguric ARF: consider mannitol 0.5mg/kg IV/IO over 2 hrs, repeat every 6-12 hrs
-RATES MUCH LOWER THAN MAMMALS BC LOWER METABOLISM - monitor urine production:
-voided, ultrasound, catheterization
-will be much much slower than a mammal!!! (12 hours no pee for a cat = 3-4 days for reptiles (7x slower))
describe treatment of hyperuricemia
allopurinol
-inhibits xanthine oxidase and blocks uric acid production
describe treatment of hypocalcemia
- calcium supplementation:
-IV, IO, or IM
-avoid unless severe: could cause hypocalcemic tetany due to Ca P product
-dangers of increased solubility index, could cause mineralization
-concurrent diuresis and titrate Ca dose
-oral calcium carbonate
-safer than parenteral routes!!!
-generally 500mg/kg/day
-give with food (competes with phosphorous)
-avoid oral/injectable D3; instead rely on exposure to sunlight
describe treatment of hyperphosphatemia
- due to phosphate retention and secondary renal hyperparathyroidism
- use phosphate binders to reduce plasma levels
-aluminum hydroxide 15-45 mg/kg PO every 12 hours
-do not give with oral calcium or food!! give in between meals
-aluminum toxicity unknown in reptiles
describe appropriate husbandry following a diagnosis of renal disease
- maintain appropriate thermal gradient (POTZ)
- increase water provision and maintain humidity
-increased spraying/sprinkler
-daily soaks
-inject tap water into dead rodents
-soak herbivorous foods - improved monitoring:
-food/water consumption
-weight and BCS
-serial clincopathology, and repeat renal assessments - nutrition:
-dietary regulation of nitrogenous wastes (urea, uric acid)
-decrease protein load of diet: avoid purines (urea and uric acidproduction) and pyrimidines (NH4 production)
-just rly avoid high protein diet in general
