LA CKD Flashcards
what are predisposing factors to CKD?
- prior acute injury
- acquired renal infection (bilateral or unilateral)
- congenital disease
- age
- the inciting cause is rarely determined, just a vicious cycle of nephron loss
-but still take a thorough history to try to understand more!
describe the general mechanisms of CKD in large animals
- tubulointerstitial disease: most common in LA
- glomerular disease: related to prior infections
- vascular insult/vasomotor nephropathy
describe GFR
an index of the functional renal mass
-volume of plasma being filtered through glomeruli per minute
adult horses and donkeys: 1.5-2.5ml/kg/min
healthy foal: 2.13
reduces with age!
creatinine is the best estimate of GFR in large animals!
describe serum creatinine
- imperfect, but the best we got, as a measurement of GFR
- source: muscle metabolism
-we’e got some beefy large animals that might just live out of the reference range in health, so having a baseline measurement is helpful! - in health: production and excretion are constant in individuals, no reabsorption (except in goats)
- increase above reference interval once 75% of renal functional mass is lost a9but not very sensitive)
-consider assay interferences: hemolysis, lipemia, icterus, BHB, glucose, vitamin C, cephalosporins
how is equine/ruminant urine unique?
- pH is 7.5-8.5 (alkaline)
-due to diet: low sodium, variable calcium, variable protein
-calcium carbonate crystals are normal in horses! - lower ability to concentrate urine:
-USG cutoff >1.025 - normal horse urine has mucoid consistency thanks to goblet cells in the renal pelvis and proximal ureter
what would make a USG difficult to interpret/false increase?
- active urine sediment
- large magnitude or proteinuria
- inflammatory cells
describe the pathophysiology of CKD
- loss of kidney function over time as there is progressive loss of renal fucntional mass
-when 2/3 of nephrons are affected there is a loss of concentrating ability
-when 3/4 on nephrons are affected there is azotemia - loss of urine concentrating ability so tubular fluid is excreted unchanged, there is isosthenuria
-hallmark of CKD in horses! - retention of nitrogenous and other metabolic end properties = azotemia
- alteration of serum electrolytes results in hyponatremia, hyperkalemia, hypochloridemia, hypophosphatemia, and hypercalcemia
- dysfunction of hormone systems decreases erythropoietin and results in anemia
- activation of RAAS in response to reduced GFR causes hypertension
how is CKD different in horses?
- hypercalcemia and hypophosphatemia are common
- PTH in horses with CKD is below limit of detection
-dietary management (switch from legume grass to grass hay) can rapidly reduce hypercalcemia - hypercalcemia is due to loss of tubular function
- kidney in the NORMAL horses excretes LARGE AMOUNT of calcium carbonate crystals!!
- NEITHER hypophosphatemia or magnitude of hypercalcemia are associated with prognosis
describe etiology of CKD
- congenital/developmental abnormalities: present younger bc less nephrons to lose
- tubulointerstitial diseases: chronic interstitial nephritis
- immune-mediated disease affecting the glomerulus: glomerulonephritis
what are clinical signs of chronic kidney disease in horses?
- subclinical/incidental finding on a colic workup is most common!
- weight loss in 80%
- mild to moderate PU/PD in 42%
-an endocrine disorder is a much more common cause of PU/PD than CKD - poor performance/lethargy
- oral or GI ulceration
- poor appetite
- dental tartar/plaque/fishy smell to breath
- ventral edema (glomerular disease): LATE in disease course
describe diagnosis of CKD in horses
- key tests:
-serum or plasma biochemistry
-UA
MUST HAVE: increased serum creatinine (>2mg/dl) and isosthenuria (1.008-1.014)
-azotemic and isosthenuric = hallmark
-must be documented for at least 3 months!!
other clues:
-hypercalcemia!!!!!!!!
-hyponatremia
-hyperkalemia
-hypochloridemia
-hypophosphatemia
-hypoproteinemia
and/or proteinuria
describe additional diagnostics of CKD
- imaging: renal ultrasound
-nephrolithiasis
-small, hyperechoic irregular capsule - assess tubular function: urinary fractional excretion (Fe) of electrolytes
-sodium (FeNa) should be <1%
-kidneys should absorb most of the sodium presented! - assess glomerular function
-UPC should be <1.1, usually less than 0.5
-should NOT be performed in patients with active urine sediments because if large particles let out of urine, kidneys already damaged
when do most horses present with CKD?
stage 3 and 4 so already significant damage and clinical signs
describe treatment of CKD in horses
- avoid nephrotoxic agents!!
- isotonic fluid diuresis: ONLY if acute on chronic
-beware overhydration! - promote water intake and polyuria!
- omeprazole: treat/prevent gastric ulcers
- diet: goal is palatability and to maintain weight
-protein restrictions usually not necessary in horses
-grass is best: palatable and high water content
-CAREFULLY consider diets high in calcium
-promote weight gain with fat and carbohydrates
-omega fatty acids - consider for hypertension or proteinuria:
-ACEi: benazepril
how do you manage a horse with CKD?
- routine monitoring approx every 3 months
-creatinine
-UA
-UPC
-BP - medications:
-ACEi
-course of corticosteroids if glomerulonephritis - supportive:
-increase water intake
-promote diuersis
-omeprazole: proton pump inhibitor - owner monitoring: QOL
-appetite
-activity level
-PU/PD
-weight
