CKD in Small Animals Flashcards
definition of CKD
structural &/or fxnl abnormalities of 1+ kidneys continuously present for >3 mos
Renal dz is characterised by
- permanent reduction in no. of fxn’ing nephrons
- evidence of structural & fxnl derangements
CKD is an… dz
ireversible, progressive dz
What population of dogs is more commonly affected by CKD
older dogs
What breeds of cats are more prone to CKD
Maine coon, abyssinian, siamese, russian blue, burmese
Causes of CKD in dogs
- familial & congenital conditions
1. chronic tubulointerstitial nephritis
2. glomerulonephropathy
3. amyloidosis
Causes of CKD in cats
- tubulointerstitial nephritis
- glomerulonephropathy
- lymphoma
- amyloidosis
CKD is a syndrome secondary to…
loss of kidney fxn
impaired glomerular, tubular, endocrine fxns leads to
retention of toxic metabolites & body fluid imbalances
Clinical presentation of CKD
- PU/PD
- anorexia, nausea, V
- oral ulceration, stomatitis, necrosis, halitosis
- D/melena, haematochezia
- wt loss/cachexia
- lethargy/depression
- urinary incontinence
- anaemia
primary fxn of kidneys
maintain water & electrolyte balance
decline in GFR means there is an increase in…
excretion of water & electrolytes per nephron
80% reduction of GFR does NOT impair
Na, K, water balance
disturbed excretion of electrolytes & water have limited compensatory mechanisms meaning…
failure towards end stage
clinical manifestation of disturbed excretion of electrolytes & water
- oedema
- hypertension
- hyponatraemia
- hyperkalaemia
- hyperphosphataemia
- metabolic acidosis
CKD has a what main clinical consequences?
- disturbed excretion of electrolytes & water
- reduced excretion of organic solutes
- impaired renal hormone synthesis
- arterial hypertension & CV consequences
- renal secondary hyperparathyroidism
glomerular filtration of solutes is done by
tubular reabsorption
abnormalities due to reduced excretion of organic solutes
- inhibition of Na-K-ATPase
- inhibition of platelet fxn
- leukocyte dysfxn
- insulin resistance
- loss of RBC membrane lipid asymmetry
Renal hormone synthesis normal includes secretion of…
EPO, calcitriol, prostaglandins, renin, kinins
Calcitriol is the most metabolically active form of…
Vit D
Vit D def leads to
renal secondary hyperparathyroidism
PTH has been id’d as a
uraemic toxin leading to renal osteodystrophy
EPO def leads to
chronic non-regen anaemia
CKD is the most common cause of secondary…
hypertension in dogs/cats
secondary hypertension causes
- target organ damage - eyes, kidney, heart, brain
- proteinuria
- cardiac remodelling
fluid retention is the main cause of
hypertension in humans w/ CKD causing haemodialysis
diuretics are used to manage…
fluid overload to control hypertension
what are arterial hypertension & CV consequences of CKD?
- secondary hypertension
- fluid retention
- activation of RAAS
ischaemia/vascular lesions cause the enhancement of
renin secretion
activation of RAAS causes what in cats
retention of salt (elevated aldosterone, low renin)
ACEi are ineffective in…
cats
Pathogenesis of secondary renal hyperparathyroidism
- PO4 retention secondary to GFR decline -> elevation in FGF-23
- limits PO4 retention, inhibits 1-alphaH activity -> decreased calcitriol
Clinical consequences of renal secondary hyperparathyroidism
- renal osteodystrophy - uncommon cats/dogs –> bones of skull/mandible mostly -> demineralise & fibrous tissues (rubber jaw)
- cystic bone lesion, bone pain
- nephrocalcinosis - loss of renal fxn
diagnostic eval of CKD
- confirm presence of kidney dz
- differentiate btw acute vs chronic
- ID biochem & haemotological complications
- determine type &/or cause of CKD
- ID presence of comorbidities
- Stage
What biochemical values should you use to determine CKD?
- creatinine
- BUN
- SDMA
- USG
- UA & culture
- electrolytes - P, K, Ca
serum creatinine conc is a surrogate for…
GFR - minimum reabsorption
serum creatinine conc is insensitive in estimating…
GFR
every time GFR decreases by half, the S-creat…
doubles
S-creat conc is influenced by…
muscle mass
BUN is a surrogate for
GFR but is less specific/sensitive than Creatinine
BUN is a surrogate for all…
uraemic toxins
What is the goal of a low protein diet?
to limit uraemic toxin prod’n
BUN can increase w/
GI ulcers/bleeding
enhanced protein catabolism
dehydration/pre-renal azotaemia
drugs
BUN low can be assoc’d w/
starvation
decreases in BUN can be impacted by which organ impairment/failure?
liver (hepatic failure, PSS)
SDMA is a produce to
protein degradation (methylation of arginine)
What % of SDMA is eliminated by glomerular filtration?
90%
SDMA is an ideal
biomarker
SDMA concentration correlates w/ what in dogs/cats?
GFR
SDMA is minimally impaired by…
muscle mass
USG should be obtained…
at the same time as blood
USG is essential to differentiate
pre-renal from primary renal
Dogs have primary renal azotaemia if USG is
<1.030
Cats have primary renal azotaemia if USG is
<1.030
Adv’d CKD causes USG to be…
isosthenuric b/c kidneys no longer modifying urine conc from plasma conc
complete UA & culture is mandatory for…
staging of CKD
Why does hyperphosphataemia occur in CKD
- decline in GFR = retention of phosphate = hyperphosphataemia as compensatory mechanism initially
Serum PO4 conc is directly linked to…
mortality in cats/dogs/humans w/ CKD
Higher PO4 conc in cats predicts…
progression to Stage III
reduced intake of PO4 is the only way to control & limit
PO4 retention
metabolic acidosis promotes…
anorexia, V, lethargy, muscle wasting, & wt loss
how do kidneys normally maintain acid-base balance?
tubular excretion of H via ammonium or PO4 & reabsorption of bicarb to maintain balance
when excretion of ammonium decreases w/ GFR it leads to
acidosis
Acidosis leads to
decreased PO4 & sulfate compound excretions + impaired tubular proton secretion
What is not typical of k9/fel CKD?
reduced reabsorption of bicarb
metabolic acidosis is commonly associated w/
Fanconi syndrome
how does iCa respond in CKD
increased or decreased
but lower in cats w/ CKD than healthy cats but tCa may be hypercalcaemic
HypoK is common in
cats w/ CKD
NOT IN DOGS
HypoK can induce
- a decline in GFR -> Na restriction -> activation of RAAS -> enhanced kaliuresis (+ hypertension), reduced food intake, dehydration
- DDX: Primary hyperaldosteronism in geriatric cats
how do you differentiate primary hyperaldosteronism from CKD
Aldosterone:renin ratio (elevated) + imaging
haematology of CKD may show
non-regen anaemia
testing required for CKD
- haematology
- serum biochem
- UA/culture
- Blood gas & electrolytes
- BP
- UPC
- rads, U/S
- infectious dz screening: UTI +/- pyelonephritis; lepto; borrelia; fip
- any specialised tests PRN
AKI vs CKD
AKI: potentially reversible once injury corrected due to adaptive/compensatory mechanisms
CKD: irreverisble & progressive loss of kidney fxn for 3+ mos
staging of CKD is based on…
P’s creatinine or SDMA
Stage 1/2 CKD
non-azotaemic (1)/ mild azotaemia (2)
no clin signs or mild (PU/PD, wt loss, selective appetite)
clin signs assoc’d w/ underlying cause (pyelonephritis, nephrolithiasis)
clin signs secondary to complications (proteinuria, hypertension)
proteinuria & hypertension can be detected at
any stage
mgmt of CKD
Supportive conservative medical mgmt
- ameliorate clin signs
- improve fluid deficits/excesses
- electrolyte, acid-base, nutritional balance
Diet therapy of CKD
- renal diets have the greatest benefit
- Omega 3’s/antioxidants - dogs
- protein restriction?
commercial renal diets limit
phosphate intake - indicated for Stage 2 p’s to slow progression & reduce mortality
it is best to initiate the conversion to a renal diet prior to the onset of…
nausea
phosphorous mgmt in CKD
- intake must be reduced as GFR decreased to avoid retention
- diet PO4 restrictions
- intestinal binding agent to trap PO4 in intestines & prevent absorption (Aluminum hydroxide)
What is a caution w/ Al-containing products for PO4 management?
- Decreased palatability & cause constipation
- toxicosis in adv’d CKD in dogs
Lanthanum is used as a
PO4 binder
Why is Al hydroxide sometimes used over Lanthanum?
cost
Ca-based chelating agent used for PO4 mgmt
Calcium carbonate
Calcitriol is used in PO4 mgmt to…
reduce PTH lvls
how does dehydration occur in CKD
if PU is not compensated by PD & water intake
dehydration can promote…
poor appetite, lethargy, constipation, pre-renal azotaemia/AKI (dz progression)
dehydration can be worsened by…
V/D
SQF can be admin’d in
chronically dehydrated P’s (cats»dogs)
Why are SQF good for CKD?
balanced electrolyte sln
how often should SQF be given?
q 1-3 days
What is the dose of SQF for cats?
75-125 ml/dose; can be increased but caution w/ fluid overload
GI mgmt in CKD
- anti-emetics
- appetite stimulation
- O-tube or gastrostomy feeding tube
what class of anti-emetic therapy is ideal?
proton pump inhibitors
the chemoreceptor trigger zone is stimulated by
uraemic toxins causing Nausea & V
What drugs act on the CTZ (chemoreceptor trigger zone)
maropitant
ondansetron
What is an appetite stimulant commonly used in CKD?
mirtazepine
adverse effects of mirtazepine
hyperexcitability, tremors, vocalisation
signs of hypertension
lethargy, blindness, retinal haemorrhage, retinal detachment, seizures, stupor, cardiac remodeling (ventricular hypertrophy)
hypertension is assoc’d w/
proteinuria - promoting progression of CKD
indications for therapy of hypertension
- treat &/or prevent target organ damages
- 180 mmHg > BP >160 mmHg - rechecked 3x over 2 mos to confirm persistence
- BP > 180 mmHg - recheck w/i 1-2 wks & if confirmed = severe hypertension
- stages I-IV w/ confirmed or severe hypertension
guideline for txt of hypertension
- reducing BP <180 mmHg except in p’s w/ severe acute ocular or neuro lesions
drugs used in a stable dog for hypertension
- ACEi - Benazepril/enalapril
- Add Ca channel blocker - Amlodipine
- Add Angiotensin receptor blocker (ARB) - Sartan
Note: may discontinue ACEi prior to Sartan or monitor closely for HyperK, Hypotension, azotaemia
Drugs used in stable cat for hypertension
- Ca channel blocker - Amlodipine
- ARB - Sartan
mgmt of anaemia in CKD
- erythrocyte stimulating agents (Darbopoetin)
Managing progression of CKD
- diet + increasing Rx PRN
- control BP
- control proteinuria
- control phosphorus lvl
- monitor QOL
- restage when uraemic crisis & azotaemia worsens
