Equine Urinary Medicine Flashcards
What are haemodynamic causes of acute renal failure?
– Hypovolaemia e.g. colitis, sweat, blood loss
– Volume redistribution e.g. effusions
– Decreased cardiac output
– Altered vascular resistance e.g. sepsis and endotoxaemia
What are renal causes of acute renal failure?
- Primarily acute tubular necrosis secondary to ischaemia or nephrotoxin exposure
- Less commonly glomerulonephritis
-e.g. immune mediated (EIA) or post-infection e.g. Strep. Equi - or interstitial nephritis e.g. pyelonephritis
How can ischaemia cause ARF?
- prolonged haemodynamic changes, renal infarction, NSAID administration
- large blood flow (20% cardiac output)
- Only 10 to 20% of blood flow to the kidneys reaches the medulla - more susceptible to ischaemic injury
What are examples of nephrotoxins?
- antibiotics e.g. aminoglycosides (gentimicin), polymixin B,
tetracyclines - Endogenous substances e.g. haemoglobin and myoglobin
- Others e.g. NSAIDs, heavy metals
What should be monitored on potentially nephrotoxic drugs?
- Serum Creatinine
-treat aggressively if rises significantly
How does aminoglycoside nephrotoxicity occur?
- Neomycin is the most nephrotoxic
–gentamicin & amikacin similar - Filtered by the glomerulus (no metabolism - all excreted by the kidneys)
- Reabsorbed by proximal tubular epithelial cells
- Accumulation in proximal tubular cells interferes with cells function
- Pre-treatment with calcium may reduce nephrotoxicity
How does NSAID toxicity occur?
- Toxicity due to renal medullary crest and papillary necrosis and sloughing of the tubular epithelial cells in the kidneys
- Dose dependant effects
- Secondary to ischaemia 2ary to prostaglandin (PGE2 & PGI2 or COX 1) inhibition
What are CS of nephrotoxicity?
- Usually referable to the primary problem
–e.g. acute colic or colitis - Anorexia and depression
–Uraemia, fluid, electrolyte & acid-base disturbances - May be just a worsening of the primary problem, or an apparent lack of response to therapy
How is nephrotoxicity diagnosed?
- Hx, CS
- Urinalysis
- Serum Biochemistry - increased BUN + creatinine
How do you treat nephrotoxicity?
- IV fluids to improve renal perfusion, correct metabolic disturbances + induce diuresis
-replace loss + 2x maintenace if polyuric - Discontinue nephrotoxic drugs
- Monitor BW, PCV, serum protein + biochem
- Poor prognosis if poor initial response to fluid therapy
How do you treat nephrotoxic horse if oliguric?
- Furosemide (4x a day)
- Dopamine - renal vasodilator
(synergistic)
What are examples of chronic renal failure in horses?
- Glomerular disease is seen more as chronic vs. acute renal failure
- Acute tubular necrosis may progress to chronic interstitial nephritis
- Other acquired include renal neoplasia (e.g. adenocarcinoma, lymphoma), amyloidosis
What are CS of chronic renal failure?
- Chronic weight loss
- Lethargy, poor hair coat, PU/PD, poor performance (mild anaemia)
- May see oral ulceration, gastroenteritis, excessive tartar and halitosis
- Ventral oedema inconsistent
–hypoalbuminaemia relatively mild and offset by increase in globulins, except for glomerulonephritis
How is Chronic renal failure diagnosed?
- Persistent isothenuria (1.008-1.014), with azotaemia + CS
- Mild anaemia + hypoalbuminaemia
- Electrolyte abnormalities =
-hyperalcaemia
-hypophosphataemia
-hyponatremia
-hypochloride
-low bicarbonate
What is treatment of chronic renal failure?
- Palliative
-improve nutrition + lower protein
-Decrease calcium (avoid alfalfa)
-ensure water + salts always available - if creatinine >800U/L = grave prognosis
