CKD Flashcards
What is the “trade off hypothesis” and how does it lead to spontaneous progression of CKD?
The renal adaptive processes that maximize kidney function to sustain homeostasis result in ongoing damage to the surviving nephrons. Therefore, CKD can progress even if the initial disease process or insult is cured
What is the prevalence of CKD in canine and feline populations?
Feline: 1-3% of US cats
Canine: 0.5-1.5% of US dogs
For serum creatinine to increase, what percent of kidney function must be lost?
75% of function in both kidneys
Why do kidneys become smaller with CKD?
Functioning nephrons are replaced by scar tissue and chronic inflammation
The majority of cats (70%) and dogs (60%) with CKD display what histopathologic changes in renal biopsy?
Tubulointerstitial nephritis
What is the MST of cats with IRIS Stage II CKD? Stage III? Stage IV?
Stage II: 1,151 days
Stage III: 679 days
Stage IV: 35 days :(
What factors influenced survival time in cats with CKD?
IRIS stage, serum phosphorus, severity of proteinuria
In all dogs with CKD, what was the MST? Dogs with IRIS Stage III and IV had how many times greater risk of mortality?
226 days
Stage III = 2.6 times the mortality
Stage IV = 4.7 times the mortality
What factors are associated with prognosis in dogs with CKD?
Proteinuria, hypertension, BUN, lower body condition score do worse
What are the histopathologic changes that accompany uremic gastritis in dogs?
Mineralization of mucosal and submucosal blood vessels, edema, glandular atrophy
What gastric hormone is increased in CKD due reduced renal clearance?
Gastrin - however, increased gastric pH typically does not occur in CKD patients
What are the clinical signs of uremic stomatitis?
- Dry mucous membranes (xerostomia)
- Oral ulcerations: usually buccal mucosa and tongue
- Brown discoloration of the dorsal surface of the tongue
- Sloughing and necrosis of the anterior portion of the tongue from arteritis
- Urine smelling breath
What factors contribute to the decreased urine concentrating ability observed in CKD?
- Increased solute load per surviving nephron => solute diuresis
- Disruption of the renal medullary architecture => disruption of the counter current multiplier system
- Impaired renal responsiveness to ADH
Why might the kidneys develop impaired responsiveness to ADH?
- May be due to an increase in distal renal tubular flow rate, which limits equilibrium of the tubular fluid with the hypertonic medullary interstitium
- Uremia may also impair ADH-stimulated adenyl cyclase
As urine concentrating ability is lost, what determines urine volume?
Daily urine solute load - sodium and urea
- Can modify the diet to alter this
What are the major mechanisms that contribute to hypertension in CKD?
- Fluid retention
- Activation of RAAS
- Increased activity of the sympathetic nervous system
What transcription factor regulates EPO synthesis in the kidneys?
Hypoxia inducible factors, especially HIF-2
What percent of asymptomatic cats with CKD have evidence of renal secondary hyperparathyroidism? What is the overall prevalence in all CKD cats?
47% of asymptomatic cats
84% of all CKD cats
What is urea synthesized from?
Synthesized using nitrogen derived from amino acid catabolism
What is urea metabolized to?
Ammonia and amino acids + CO2
Hyperphosphatemia occurs when GFR declines below what percent of normal?
Below 20% of normal
Why might total calcium increase but ionized calcium decrease in CKD?
Increased calcium binding to organic acids (citrate, PO4, sulfate) that are not being excreted due to CKD
What may the cause of hypokalemia in cats with CKD?
- Decreased dietary sodium may activate RAAS and promote kaliuresis => hypokalemia
- Decreased food intake
What are the consequences of hypokalemia in CKD cats?
- Anorexia
- Muscle weakness
- Worsening kidney function (reversible, functional decline in GFR) - improved with K supplementation
What RAAS system abnormalities have been identified in CKD cats?
Low plasma renin, but high plasma aldosterone concentrations
How is SDMA formed in the body?
The process of protein degradation includes methylation of arginine into various substances, including symmetric dimethylarginine (SDMA)
Why is SDMA a good marker of GFR?
> 90% eliminated by the kidneys
Freely filtered across the glomerulus without tubular reabsorption
How much kidney function must be lost for SDMA to be elevated?
30-40% decline in function (earlier marker than creatinine)
In dogs and cats with CKD, how much sooner does SDMA increase compared to creatinine
Cats: SDMA increased 17 months before creatinine
Dogs: 10 months
How long must kidney function be decreased to call it chronic kidney disease? Why?
> 3 months
It can take up to 3 months for renal compensatory hypertrophy to occur after an AKI
Staging CKD should be based on what?
A minimum of 2 stable creatinine values obtained when the patient is fasted and well hydrated, obtained at least a few weeks apart
When should pets with borderline proteinuria be re-evaluated?
In 2 months
Name 5 benefits of a renal diet
- Low sodium and phosphorus
- Added B vitamins
- Increased caloric density
- Soluble fiber
- Neutral effect on acid/base balance
- Omega-3 fatty acids/antioxidants
Limiting dietary phosphorus is indicated for what IRIS stages of CKD?
II through IV
Limiting dietary protein is indicated in what IRIS stages of CKD?
III and IV in dogs
II through IV in cats
In dogs with CKD fed a renal diet vs a maintenance diet, what was the symptom free interval? Risk of death and MST?
- Symptom free interval 600 days vs 250 days
- Risk of death from renal causes reduced by 69%
- MST 600 days vs 190 days
In cats with CKD fed a renal diet vs a maintenance diet, what was the MST?
MST 630 days vs 264 days
When should phosphorus be rechecked after starting a renal diet?
4-6 weeks, if no improvement, add binding agent
What are the clinical signs of aluminum toxicosis in patients on aluminum containing phosphate binders?
Cranial, peripheral, junctional neuropathies - ataxia, weakness, absence of patellar reflexes, decreased withdrawal, tetraparesis
When should bicarbonate supplementation be considered?
Plasma bicarbonate <15 mmol/L
What are two oral options for alkalization therapy?
Potassium citrate and sodium bicarbonate