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
Epidemiology
prevalence: ~500k
higher incidence among select racial groups
-african-americans
-native americans
Etiology
most common causes: -diabetes mellitus -hypertensive nephrosclerosis -chronic glomerulonephrotis Other -polycystic kidney disease (familial) -glomerular/vascular/tubular/interstitial disease
progressive renal disease
- irreversible damage of select glomeruli
- intact glomeruli hyperfiltrate
- high blood flow
- glomerular hypertension
- high pressure damage to remaining glomeruli
- increased permeability to protein –> proteinuria
- nephrosclerosis - scarring
what is the homeostatic function?
volume regulation (tonicity) -Na* handling water balance acid handling potassium handling
clinical manifestations
- hypervolemia- excess volume
- (Na+ & H2O retention)
- hyponatremia (low Na+ concentration)
- excess water = hypo-osmolality
- hyperkalemia- excess potassium
- metabolic acidosis- excess acid
- anemia- low hemoglobin
- prolonged bleeding time
- renal bone disease
- uremia
renal Na+ handling
net Na excretion: <1% (150 mEq/day)
describe the clinical and physical findings of hypervolemia
decreased Na excretion - dec. GFR -> Na and H2O retention physical findings -hypertension (HBP) -shortness of breath due to pulmonary edema (fluid in the lungs) -peripheral edema (swelling of the legs)
describe the clinical findings of hypertension
high pressure at the glomerulus
-increases kidney damage
increases protein in the urine (abnormal)
greater cardiovascular morbidity and mortality
Describe the aspects of renal water handling
filter: 140 L per day reabsorption: -70% proximal tubule -15% descending limb of loop of henle -collecting duct: antidiuretic hormone (8L - 19.5L)
describe the clinical presentations of hyponatrmia
- poor H2O excretion due to compromised tubular function (poor urinary diluting function)
- mostly in the setting of excess free water intake
- confusion, seizures with severe derangements
describe acid handling
- acid generated with protein rich diet, metabolic processes
- protein -> sulfuric acid/phosphoric acid
- daily “cid intake” ~ 60-120 mEq
- kidneys regulate and eliminate H+
- buffering of H+
- excretion
Proximal tube and distal tube are used for?
reabsorption of HCO3 and secretion of H
normal levels of H+ are 40 nEq but acidemic states lead to
increase protein breakdown
decrease cardiac (myocardial) function
increase risk of arrythmias (abnormal heart rhythm)
increase bone resorption (breakdown)
impaired O2 uptake by hemoglobin (in red blood cells) in the lungs
potassium homeostasis
k+ homeostasis important for normal cellular function
-determines resting cell membrane potential
-depolarization of muscle and neural cells
normal K+ :
-60mEq/Kg body weight
-daily intake: ~50-150 mEq/day, normal plasma K 4 mEq/L
-90% absorbed
-immediately K is shifted from blood to inside cells until you can excrete into the urine
renal potassium handling
filtration -glomerulus reabsorption (~100%) -proximal tubule -thick ascending loop of henle -almost no K reached distal tubule excretion** -active K+ secretion
describe the clinical findings of hyperkalemia
decrease GFR and secretion leads to K+ retention and so cardiac arrest
renal hormonal function
erythropoeitin vitamin D -stimulate Ca2+ *absorption from the gut -parathyroid hormone suppression *parathyroid hormone stimulation causes bone breakdown
descibe the clinical presentations of anemia
- hormonal function
- dec. erythropoeitin production
- poor oral iron intake
name the three possible treatments for anemia
transfusion
erythropoeitin therapy
iron replacement
what is the function of vitamin D?
it is needed to absorb calcium from food
renal osteodystrophy
poor bone formation due to:
- hyperphosphatemia resulting in increased PTH
- poor filtration of phosphorus
- bone breakdown stimulated by PTH
- impaired bone mineralization due to poor vitamin D activation -> low calcium
- metabolic acidosis
what is the treatment for renal osteodystrophy?
- phosphate binders
- active vitamin D
- parathyroidectomy in severe hyperparathyroididm
Bleeding
platelet disorder: uremic toxins
anemia
uremic symptoms
GI: nausea, vomiting, poor taste, decreased appetite
Skin: itching
CNS: fatigue, lethargy, depression, decreased intellectual and cognitive function, sleep disturbances
Musculoskeletal: twitching, neuromuscular irritability, leg and arm craps
Sexual dysfunction: decreased libido, amenorrhea
Inflammatory symptoms of heart: pericarditis (inflammation of heart lining), pericardial effusion
what is the treatment for uremia?
blood pressure control treatment of underlying disease -ex. diabetes mellitus lower protein in the urine -protein in urine is abnormal and indicates damage of the glomerulus
how can one control complications of CKD?
restrict Na and water in diet/diuretics
restrict K in diet
avoid excess protein in diet but would not restrict it
lower phosphate in diet with binders
activated vitamin D to suppress PTH
anemia: iron, erythropoietin, transfusion
Hemodialysis and peritoneal dialysis
hemodialysis: a method that is used to achieve the extracorporeal removal of waste products such as creatinine and urea and free water from the blood when the kidneys are in a state of renal failure
peritoneal dialysis: uses the patient’s peritoneum in the abdomen as a membrane across which fluids and dissolved substances are exchanged from the blood.
renal transplantation
- best long-term prognosis
- long waitlist
- ABO compatibility
- lifelong immunosuppression
- risk of infection
