Intro to Kidney Diseases Flashcards
define GFR
the amount of fluid filtered from the glomerulus into Bowman’s space per unit of time; a key determinant of kidney function
define azotemia
laboratory abnormality defined as an increase in nitrogenous products due to decreased renal excretion
define prerenal azotemia
- GFR is decreased due to decreased blood flow to the kidneys (hypovolemia due to dehydration or hemorrhage, circulatory shock, heart failure, etc.)
- if dehydration/volume depletion is the cause, functioning kidneys should be preserving water
-so azotemia occurs frequently with well-concentrated urine
describe renal azotemia
- GFR is decreased due to decreased function or number of nephrons (intrinsic kidney disease, either acute or chronic)
- the kidneys, typically, also fail to concentrate the urine
-azotemia occurs concurrently with minimally concentrated urine
describe postrenal azotemia
- GFR is decreased due to urinary tract blockage or urinary rupture has occurred, and urine is in the peritoneum
-increased hydrostatic pressure in Bowman’s space decreases GFR - urine concentration can vary
define chronic kidney disease
- abnormality of kidney structure or function that has been present for at least or longer then 3 months, with implications for health
- general/umbrella term for heterogeneous disorders of varying causes, histopath, severity, and rate of progression
- all disorders cause a PERMANENT reduction of the number of functioning nephrons which results in a decreased GFR (may detect this before creatinine rises)
- irreversible and slowly progressive
- predisposes to AKI
- most common form of kidney disease, more common in cats and senior animals (so hella common in OLD CATS)
define acute kidney disease
- an abrupt (within hours) decrease in kidney function, which encompasses both injury (structural damage) and impairment (loss of function)
- SUDDEN change in kidney structure, function, or both causes a decreased GFR that may be detected before creatinine rises
- potentially reversible, but not always and mortality rate is high
- predisposes to CKD
describe history and physical exam components that are supportive of AKI or CKD
AKI
1. recent change in urination
2. no change in weight/BCS
3. acute onset GI signs
4. recent reduction in appetite
5. healthy hair coat
6. normal to enlarged kidney
CKD:
1. PU/PD for >3 months
2. weight loss for >3 months
3. chronic/intermittent GI signs
4. reduced appetite for >3 months
5. poor hair coat
6. small, irregular kidneys
7. +/- chronic uremic breath, osteodystrophy, signs related to proteinuria/hypertension
describe labwork and imaging components of AKI and CKD
AKI
labwork:
1. more severe clinical signs for the same level of azotemia (no time to adjust)
2. hematocrit normal or increased
imaging:
1. normal or enlarged kidneys
2. changes in architecture vary with cause (neoplasia, obstruction, infection, etc.)
CKD
labwork:
1. clinical signs mild despite marked azotemia
2. non-regenerative (hypoproliferative anemia)
imaging:
1. small, irregular kidneys
2. degenerative changes (irregular margins, poor corticomedullary differentiation)
describe histopathology and response to treatment of AKI versus CKD
AKI:
histopathology: depends on etiology, but fibrosis is ABSENT
response to treatment: markers of GFR can improve over time (if animal survives) and even normalize in some cases
CKD:
histopathology: depends on etiology, but FIBROSIS indicative of CKD
response to treatment: after correcting for extrarenal/acute factors, markers of GFR (creatinine) tend to be stable or worsen over time
compare and contrast the short term and long term prognosis for AKI versus CKD
AKI:
short term survival: 50/50 (varies widely with etiology)
long term survival/QOL: depending on the degree of recovery/nephron loss, survivors may do very well! or may be left with advanced CKD
CKD:
short term survival: excellent if not in end-stage kidney disease
long term survival/QOL: varies according to etiology, CKD stage, and other factors, but likely life limiting (except some stage 2 cats live forever)
what are causes of CKD?
- AKI of any cause (months later)
- nepro- and ureterolithiases
- neoplasia (LYMPHOMA)
- immune complex glomerulonephritis
- glomerulosclerosis
- anyloidosis
- renal dysplasia
- polycystic kidney disease
- other congenital/hereditary familial disease
- pyelonephritis
- leptospirosis
- chronic infection wth FIV, FLV, or FIP
- idiopathic or literally so many other things
describe CKD lesions in dogs versus cats
dogs: most commonly primary lesions within the glomerulus
cats: most commonly primary lesions within the tubulointerstitial compartment
but primary lesions in any segment of the nephrons may occur in any species!
describe the biological behavior of CKD
- primary renal disease: may or may not be active at time of diagnosis
- functional maladaptations: lead to self-perpetuating worsening of disease
-reduced number of nephrons so each nephron now doing more work; how to increase GFR?
-glomerular hypertrophy and hyperfunction/hyperfiltration/hypertension but these adaptations cause ongoing damage to remaining nephrons (tubular ischemia) - superimposition of uremia: accumulation of substances normally excreted by the kidneys
GFR is decreases through each stage
in some cases there is linear progression through these stages (dogs more commonly) and in other cases there are periods of relative stability and episodes of precipitous decline (cats more commonly)
describe the functional maladaptations of CKD
the remaining nephrons undergo glomerular hypertrophy and hyperfunction/hyperfiltration/hypertension and subsequent tubular ischemia
they do this via
1. efferent arteriole constriction
2. increased single nephron GFR
3. tubular hypermetabolism
4. peritubular capillaries not providing enough O2 bc flow is limited so results in hypoxic/oxidative injury to nephrons
