Clinical Approach of Renal Dz Flashcards
What is the functional unit of kidney
nephron
What is the function of the nephron?
- regulation of volume & composition of ECF –> production of urine
- plasma ultra-filtration
What is GFR
rate at which blood circulates thru glomerulus & rate urine is produced
Changes in GFR means there is
renal dysfxn
decrease in GFR means
kidney dz
what is a common marker of GFR changes?
Azotaemia
Changes of GFR means there can be what conditions?
AKI or cKD
proteinuria is a sign of
kidney dz, specific to glomerular damages
proteinuria is independent from
a decrease in GFR
PU/PD is a sign of
renal dz
Non-specific reported clinical signs of renal dz
- lethargy
- weight loss
- anorexia/inappetence
- V
- uraemic crisis
Signs referable to systemic hypertension (more in cats than dogs)
- blindness
- hyphaemia
Potential nephrotoxicity can occur b/c of…
- toxin exposure
- infectious agents
- medications
indicators of azotaemia
- urea
- creatinine
pre-renal leads to
decreased perfusion
If USG >1.030 (dogs) or >1.035 (fel) then azotaemia is
pre-renal or higher
pre-renal azotaemia is usually caused by
dehydration
renal causes of azotaemia
CKD or AKI
post-renal causes of azotaemia
Lower UT obstruction or rupture
What is the gold standard for testing for renal dz
GFR
serum creatinine concentration is a surrogate for
GFR
Every time the GFR decreases by half, then
S-creat doubles
serum creatinine conc is influenced by
muscle mass
increases in serum creatinine means there are
irreversible losses in kidneys
S-creatinine can increase by what % after a meal?
20% - measure on fasted P
BUN is less … than creatinine
specific & sensitive
BUN should always be interpretted w/
creatinine
BUN is great for
the level of toxins & consequence of renal fxn
Low GFR means
there is an impaired ability to excrete proteinaceous catabolites (excreted by GFR)
BUN acts as a surrogate for all…
uraemic toxins, correlating w/ uraemic clin signs (V, ulcers, lethargy…)
What is the goal of a low protein diet>
limit uraemic toxin production
BUN increases w/
GI ulcers/bleeding
Enhanced protein catabolism
Dehydration/pre-renal azotaemia
Drugs
BUN decreases w/
PSS or other hepatic failure, low protein diet
SDMA has a strong correlation w/
GFR & S-creatinine
Hyperphosphataemia
- decline in GFR = retention of PO4
- Serum PO4 conc = directly linked to mortality in human, cats, dogs w/ CKD
- Ca x PO4 product = assoc’d w/ increased mortality
- Reduced intake of PO4 only way to control & limit PO4 retention
Metabolic acidosis
- common finding in CKD
- promotes V, anorexia, lethargy, muscle wasting, weight loss
- balance maintained by tubular excretion of H+ via ammonium or PO4 & reabsorption of bicarb
Reduced reabsorption of HCO3- not typical in
feline & canine CKD
Calcium
- ionised Ca can be up or down in P’s w/ CKD
- Hypocalcaemic in cats w/ CKD
- Total Ca in cats w/ CKD hypercalcaemia
K
- AKI: accumulates in blood –> life-threatening –> arrhythmias, death
- CKD: lost due to fibrosis/leak in UT, HypoK, supplement
Hypokalaemia is common in CKD of what species?
cats
primary hyperaldosteronism occurs in geriatric cats - it has what conditions?
severe hypokalaemia, polymyopathy, refractory hypertension
USG is essential to differentiate
pre-renal from primary renal dz
Adv’d CKD has what USG?
Isosthenuria (1.008-1.012), kidneys no longer modifying urine conc from plasma conc
USG < 1.006 means
not consistent w/ renal azotaemia –> urine dilution req’s proper renal fxn
Non-regen anaemia
Lack of EPO, slow progression w/ dz progression
Infectious dz screening in urinary tract
UTI +/- pyelonephritis
14-15% dogs w/ azotaemia
WBC
Lepto
Borreliosis
FIP
AKI is potentially
reversible
Chronic renal dz
irreversible & progressive loss of kidney fxn (3+ mos)
How do you diagnose chronic renal failure?
- medical hx & PE
- Hx of changes in renal values, UA (USG, Proteinuria)
- structural changes seen on imaging)
Azotaemia is NOT synonymous w/
CKD
To determine cause of azotaemia, one must…
- perform an U/A
- differentiate btw pre-renal, renal, post-renal
