Chronic Kidney Disease Flashcards
what are the three overarching functions of the kidney?
- excretory
- homeostatic
- hormonal
excretory function
water
solutes
-electrolytes
-metabolic end products
what is the basic filtering unit of the kidney?
nephron
what is the first component of a nephron?
the glomerulus
permeability or fractional clearances are dependent on?
size and charge. the smaller the molecule size, the more likely that it will get filtered (water, salts, metabolic wastes, small nutrients). The more negative a molecule the less permeable.
example molecules
albumin: negatively charged and radius is 36
dextran: positively charged
what are all of the components of the nephron?
glomerulus, convoluted tubules and collecting ducts
what are the functions of the tubules?
secretion
-cations, anions and charged compounds
-important for acid secretion and maintenance of physiological concentrations of electrolytes, and drug elimination
reabsorption
-electrolytes, glucose, aminoacids, proteins, water, urea
-recover freely filtered substances
what are the mechanisms of waste elimination?
urea (50%) -free filtration -passive reabsorption creatinine (110-115%) -free filtration -active secretion hippuric acid (~100%) -poor filtration -active secretion
what is the glomerular filtration rate (GFR)?
- the rate at which plasma is filtered across the glomerulus (ml/min)
- determines excretory and homeostatic function
- normal: ~100ml/min (range: 90-150 ml/min)
glomerular filtration rate can be associated with
- renal disease
- it is important to note that urine volume is not reflective of GFR bc tubular and secretion determines concentration of waste products
GFR measurement
-substance filtered/day=substance excreted in urine/day
-[plasma substance level] x plasma fluid filtered/day=substance excreted in urine/day
GFR:
=[urine substance level] x volume/day / [plasma substance level] : UV/P
what are the three formulas for GFR estimation?
cockcroft-gault formula: age, weight, sex and creatinine concentration
MDRD formula: creatinine concentration, age, race, sex (more reliable that cockcroft but less so at extremes of age)
CKD-EPI formula: creatinine concentration, age, race, sex
GFR and Weight
creatinine -synthesized by skeletal muscle -muscular individuals with higher levels -malnourished individuals with lower levels BUN (blood urea nitrogen) -byproduct of protein intake -poor nutrition may lower the BUN level
What is the relationship between GFR and age?
GFR declines with aging, and as a result of decreased muscle
What is the relationship between the serum creatinine and GFR?
they are inversely related
chronic kidney disease
- definition: progressive in GFR
- irreversible
- progression to end-stage renal failure (ESRD) requiring renal replacement therapy
clinical manifestations
stage 1: GFR >90 Normal
stage 2: GFR 60-90 Early Renal Insufficiency
stage 3: GFR 30-60 Chronic Renal Failure
stage 4: GFR 15-30 Pre-End Stage Renal Disease
stage 5: GFR <15 End Stage Renal Disease