Overview of Renal Function and Renal Disease Flashcards
what are the three steps of urine formation?
filtration
selective reabsorption
selective secretion
how much of the plasma moves into the filtrate?
about 20%
how much blood flow do the kidneys receive?
20% of cardiac output
what does the loop of henle create?
hypertonic medullary interstitium
what are the two capillary beds in the kidney?
glomerular
peritubular
where is 90% of renal bloodflow?
cortex
which capillary bed has high pressure?
glomerular: high hydrostatic pressure causes fluid filtration
in peritubular capillaries, _________________ favors fluid reabsorption
low hydrostatic pressure
what can regulate the respective pressures and rate of glomerular filtration and tubular reabsorption in the capillaries?
adjusting the resistance of afferent and efferent arterioles
what are some vascular born insults that can impact the kidneys?
thromboembolism
bacterial emboli
circulating immune complexes
what color are acute infarcts?
red
what color are chronic infarcts?
white
infarcts that affect the cortex and medulla likely involve _________________
interlobar vessel
infarcts affecting only the cortex could involve either __________________________
the arcuate or interlobular artery
what characterizes acute kidney injury?
sudden loss of renal function over hours or several days
potentially reversible
what characterizes chronic renal disease?
renal disease has persisted for months or years
function often progressively declines over months to years
“cure” not generally possible
at what age is chronic renal disease common?
generally older animals
congenital or familial disease seen in younger animals
what is uremia?
clinical signs associated with kidney failure
what are the signs of uremia?
anorexia, depression
dehydration
hypothermia
weight loss (chronic)
nausea
vomiting
diarrhea
what do you see with uremic gastropathy?
submucosal arteritis
edema and mast cell infiltration of submucosa
glandular atrophy
fibroplasia
mineralization
what does mineralization contribute to?
gastric ulceration
hemorrhage
hematemesis
what is uremic enterocolitis?
ulcerative and hemorrhagic lesions in colon
often bloody diarrhea
what happens with uremic stomatitis?
halitosis: bad breath
oral ulceration
what causes oral ulceration with uremic stomatitis?
vasculitis/arteritis
bacteria in mouth convert urea to ammonia
what does renal secondary hyperparathyroidism with CRD lead to?
pathologic mineralization
renal osteodystrophy
how prevalent is arterial hypertension with chronic renal disease?
50-80% of dogs and cats
what are some examples of tissue mineralization with uremia?
uremic frosting
uremic pneumonitis
uremic endocarditis
what material accumulates in an animal or person with gout?
uric acid
what predisposes patients with uremia to bleeding?
decreased platelet function with uremia
ulcerations
abnormal blood vessels
what are the consequences to bleeding tendencies with uremia?
ocular lesions
brain bleeds
gastrointestinal hemorrhage
gingival bleeding
bruising
what is renal gout?
urate crystals in renal tubules
what is visceral gout?
coating of chalky white urate crystals on internal organs
what is articular gout?
accumulation of uric acid crystals in joints and along tendons
what are the uremic effects on the endocrine system?
insulin resistance
uremic animals usually sterile
what does acute kidney injury result in?
accumulation of metabolic wastes
dysregulation of fluid and electrolyte balance
acid/base imbalance
what are the physical exam findings with an acute kidney injury?
rapid onset of clinical signs
depressed, hypovolemia, hypotension
+/- fever
tachypnea to eliminate CO2
+/- bradycardia
+/- enlarged, painful kidneys
what can cause ischemia?
severe or prolonged dehydration or hypovolemia
thrombosis or infarction
what are some causes of intrinsic damage to the kidneys?
nephrotoxins
hemoglobin or myoglobin nephropathy (more large animals)
infectious agents
hypercalcemia
what are some infectious agents that can cause intrinsic damage to the kidneys?
leptospira
ascending infections
what are some postrenal causes of acute kidney injury?
elevated pressure
acute blockage
decreased flow increases: stone formation and infection
what are the four phases of acute kidney injury?
initiation
extension
maintenance
repair
what happens in the initiation phase of acute kidney injury?
insult and sublethal injury
what happens in the extension phase of acute kidney injury?
injury continues and epithelium undergoes apoptosis or necrosis
progressive decrease in GFR, urine concentrating ability and urine output
blood test may be normal for 1-2 days
changes in urine sediment maybe
kidneys may be swollen and painful
what might you see on a UA during the extension phase?
casts
accumulation of things absorbed: glucose or protein
etiology evidence
what are some things that would be evidence of etiology on a UA of acute kidney injury during the extension phase?
calcium oxalate crystals
RBC, WBC, fungi, bacteria
what characterizes the maintenance (oliguric) phase of acute kidney injury?
irreversible epithelial damage: GFR reduced enough to show azotemia, urine output decreased
complications of uremia develop
elimination of inciting cause does not alter rate of recovery
what happens during the recovery phase of acute kidney injury?
repair and regeneration of kidney tissue
what is the duration of the recovery phase of acute kidney injury?
days to months
what is the most common type of renal disease in cats and dogs?
chronic renal disease
what has occured in chronic renal disease?
irreversible, structural changes: loss of nephrons and decreased GFR
what are some causes of chronic kidney disease?
any cause of AKI
familial/congenital
infectious disease
neoplasia
glomerulopathies
idiopathic
obstruction
what are the physical exam findings associated with chronic renal disease?
thin, poor hair coat
depressed, dehydrated
pale mucous membranes
signs of hypertension and uremic changes
+/- fever
tachypnea to eliminate CO2
+/- small, irregular kidneys
when does chronic interstitial fibrosis occur?
end-stage
severity of fibrosis correlates with rate of disease progression
how many times per day is the entire plasma volume filtered?
60x
what is the function of cortical peritubular capillaries?
reabsorption and secretion of substances
what is the function of vasa recta capillaries surrounding juxtamedullary nephrons?
osmotic exchangers for production of concentrated urine
is uremia associated with the degree of kidney dysfunction or the duration?
degree
what is the pathophysiology of uremia?
retention of nitrogenous wastes
increased intracellular Na and water
decreased intracellular K
increased levels of bioactive substances normally metabolized or excreted by the kidney
decreased levels of hormones and other mediators produced by the kidney
imbalance between calcium and phosphorous
what leads to the local effects of uremia on vomiting?
uremic gastritis
elevated serum gastrin
back diffusion of HCl and pepsin into stomach wall
what leads to the central effect of uremia on vomiting?
activation of chemoreceptor trigger zone in brain medulla
what is the pathologic mineralization of renal secondary hyperparathyroidism with CRD?
elevated phosphorous binds Ca
CaPhos precipitates into soft tissues which may be damaged/necrotic by uremic toxins
what is uremic endocarditis?
sub-endocardial mineralization of right or sometimes left atrium
what are the adverse effects of hypertension?
glomerular damage and proteinuria
ocular lesions
hemorrhages
why do you get abnormal blood vessels with chronic renal disease?
mineralization
hypertension
endothelial damage/vasculitis
what are microcrystals of uric acid in gout called?
tophi
why are uremic animals usually sterile?
elevated prolactin and luteinizing hormone
decreased testosterone, estrogen, progesterone
atrophy of germinal epithelium of testicle or ovary
what are some things that can lead to severe or prolonged dehydration or hypovolemia?
severe vasculitis
pancreatitis
gastric torsion
addisonian crisis
heat stroke
how can hypercalcemia cause intrinsic damage to the kidney?
vasoconstriction
mineralization
acute blockage causes ______________ effect on ability to concentrate urine
reversible
true/false: blood tests may be normal during the extension phase of kidney injury
true
changes in urine sediment may be seen
what hormones may play a factor in the recovery phase of kidney injury?
epidermal growth factor
TGF alpha
IGF
what do high glomerular capillary pressures lead to?
scarring and occlusion of vessels
synthesis of mesangial matrix
disruption of capillaries leads to proteinuria
