Renal Flashcards
what is the major job of the kidney?
regulate comp of body fluids/remove metabolic waste to ensure homeostasis
what is the functional unit of kidney?
nephron
what is the glomerulus?
tuft of capillaries surrounded by special type of basement membrane
what happens in glomerulus?
filtration (water/small molecules <5000 daltons are filtered into Bowman’s capsule)
why is filtrate not = to urine?
cuz of reabsorption and secretion steps
some major kidney fxns?
fluid electrolyte balance, excretion of metabolic wastes, excretion of drugs/toxins, reg acid-base balance, role in reg BP, erythropoiesis, vit. D activation
Most Na filtered by kidney gets _____
reabsorbed
majority Na reabsorbed and not regulated called ____ and this happens in _____
basal; proximal tubule
portion of Na reabsorption that can be regulated happens in:
distal convoluted tubule (aldosterone regulated)
almost all K is reabsorbed in _____
proximal tubule
any K in urine is ____ in the distal tubules in exchange for Na
secreted
ex. of metabolic wastes?
urea, creatinine, uric acid
how can diet increase urea production? Where does urea come from?
amino acids (ammonia), high protein intake, stress state, low energy diet (first priority is protein/a.a. breakdown for gluconeogensis), protein of low biological value
Vitamin D activation -OH steps happen in:
kidney and liver
important screening/diagnostic tests
BP, urinalysis (random urine protein or albumin, urine osmolality), serum urea, serum electrolytes, radiological procedures, assessment of GFR
what is ACR?
urine albumin to creatinine ratio
what is PCR?
urine protein to creatinine ratio (^ when CKD)
what is GFR?
volume of fluid filtered from renal glomerular capillaries into Bowman’s space per unit time
assessment of GFR is currently done by: ____ + _____
serum creatinine + eGFR
what is creatinine?
breakdown product of phosphocreatine (high energy reserve) in muscle
what factors determine how much creatinine is in serum?
1) produced in amounts proportional to muscle mass (going into blood) 2) depends on GFR (going out of blood)
why not just use serum creatinine?
too many other factors like muscle mass, age, sex, ethnicity, etc.
2 examples of formulas for GFR?
cockroft Gault and MDRD
CKD is characterized by:
progressive decline in kidney fxn occuring over mths/years, irreversible but can slow progression, dialysis/transplants extend life in kidney failure
etiology of CKD
DM, uncontrolled hypertension (damaging blood vessels in kidney), glomerulonephritis (inflammation in glomeruli), vascular disease (atherosclerosis affecting arteries), polycystic disease (genetic), lupus erythematosus (arthritis)
pathophysiology of CKD:
gradual decrease in fxning nephrons, cause may initially adversely affect either glomeruli or tubules, fewer remainng functional nephrons try to compensate by ^ in size and fxn, eGFR gradually decreases
signs and symptoms of CKD?
early on may be polyuria or nocturia but becomes oliguria/anuria/dysuria, foamy urine that is tea coloured, fatigue, itching, anemia, swelling of hands and feet, shortness of breath, bad taste in mouth, cold intolerance, nausea/vomiting/anorexia due to uremia, CNS symptoms
what causes CNS symptoms?
untreated uremia (buildup of urea/other byproducts of protein metabolism)
as GFR decreases, serum Phosphate ____, serum Ca ____, secretion of PTH ____
increases; decreases; increases
secondary decrease in Ca absorption?
impaired renal hydroxylation of 25-OH cholecalciferol
contributors to renal osteodystrophy (bone pain and fractures) are:
acidosis, excess PTH, altered vit D metabolism
treatment for CKD:
control BP, detect microalbuminuria and treat with drug therapy, control HbA1c, cease smoking, reduce dyslipidemia, nutr care, dialysis, renal transplants
2 types of dialysis:
hemodialysis and peritoneal dialysis
this dialysis involves an artificial kidney machine or dialyzer to remove unwanted substances from blood stream (permanent access to bloodstream), there are diff forms of vascular access
hemodialysis
rates and amounts of fluid/waste products removed can be varied by using diff:
membranes, blood flow rates, dialysate concentration
v total blood volume causes:
hypothalamus stimlate release of antidiuretic hormone from posterior pit gland –> ^ water reabsorption
regulation of BP is through ____ system
renin-angiotensin
what is urine osmolality?
ability of kidney to concentrate or dilute urine
ideal nuclear medicine method marker?
endogenous, freely filtered, not secreted/reabsorbed, inexpensive to measure
approx eGFR for young adults is:
120-130 mL/min/1.73m^2
malnutrition potential begins at stage ___ of CKD
3
why add glucose in dialysate?
prevent hypoglycemia
excess fluid is removed in hemodialysis by ___
ultrafiltration
what is the peritoneum?
membrane that lines ab cavity and surrounds ab organs, forming sac
how does peritoneal dialysis work?
dialysate enters peritoneal space thru catheter penetrating ab wall –>clamped so fluid remains in peritoneum, drain after given amount of time
peritoneal dialysis relies on exchange with _____ in the ____
circulating plasma ; capillaries
peritoneal similar to hemodialysis principles except:
dialysate contains enough glucose to make it hypertonic relative to plasma, causing fluid to flow into peritoneal cavity
efficiency of peritoneal dialysis determine by:
concentrations in dialysate, dwell time (amt of time dialysate in the peritoneal cavity)
2 major types of peritoneal dialysis :
continuous ambulatory peritoneal dialysis (CAPD), continuous cycling peritoneal dialysis (CCPD)
what is CAPD?
repeated infusions of dialysate into peritoneal space–> dialysate stays in peritoneal space for 4-6 hours, drained by gravity–>repeat (long dwell time overnight) –>note that kids would get this
what is CCPD?
machine does repeated timed cycle of infusion, dwell, and drain at night automatically, dialysate left in peritoneal cavity during day, then drained by gravity and repeated
normal/goal values for Na:
135-146 mmol/L
normal/goal values for K:
3.5-5.1 mmol/L
normal/goal values for P:
0.70-1.53 (<1.78)mmol/L
normal/goal values for Ca:
2.10-2.55 mmol/L
normal urea values :
3.7-7 mmol/L
normal creatinine values:
45-125 (m) and 45-110 (f) mmol/L
normal albumin values:
35-52 g/L
normal HCO3 values:
22-31 mmol/L
normal PTH values?
1.3-7.6 (16-50) pmol/L
what is a fistula?
anastomosis of artery and vein shunting arterial blood into vein
medications commonly used in Renal disease
antihypertensives, diuretics, lipid lowering agents, phosphorus binders, vit D analogues (later stages), sodium polystyrene sultanate, human recombinant erythropoietin, nutrition support for ^ erythrocyte production (iron, B12, folate)
why take P binders with meal?
bind phosphate and prevent absorption from GIT (Al or Ca based usually)
what is sodium polystyrene sulfonate?
cation-exchange resin to bind K if serum K is high
major cause of anemia in CKD?
v erythropoietin production = v erythrocyte production = anemia (also can be blood losses associated with testing and dialysis, diet factors)
objectives of nutrition care?
1) maintain optimal nutrition status 2) minimize metabolic disorders and related symptoms (reduce intake of substances can’t excrete well, provide replacements for compounds lost in ^ quantities) 3) slow progression of disease
causes of protein-energy malnutrition in advanced CKD/dialysis?
poor food intake (anorexia by uraemia, altered taste, unpalatable prescribed diets), catabolic response to illness/inflammation, loss of nutrients and promotion of protein catabolism through dialysis, endocrine disorders of uraemia (insulin resistance), accumulation of uremic toxins
factors that ^ muscle catabolism and ^ uraemia?
inadequate energy intake, inadequate protein intake, unbalanced protein
what happens as protein metabolism changes?
protein byproducts ^–>anorexia/nausea –> v intake –> ^ muscle protein catabolism –> ^ uremia and tendency toward - nitro balance and muscle wasting (stimulated by metabolic acidosis)
how to deal with metabolic alterations of protein from nutrition point of view?
not provide excess to prevent accumulation of end products–>match diet protein with v workload capability of kidneys (but note small increase in protein requirement in earlier stages p.t. protein-energy malnutrition)
why difference in energy requirements based on age?
body comp changes–>v muscle mass (which is biggest impact in RMR), v activity
protein recommendations assume:
energy needs being met by nonprotein sources
why is serum urea nonspecific?
affected by v Renal function, ^ protein intake, inadequate energy intake
anthropometric assessment for protein-energy status:
wt corrected for height, BMI, mid arm circumference
biochem assessment for protein - energy status:
serum albumin
why serum albumin not super accurate measure protein status?
cuz chronic inflammation affects this value more than protein status (masking effect)
monitoring tools for na and water retention
edema, serum Na, urine volume, BP , body weight
fluid recommendations stage 3 and 4:
restrict prn
if diet Na v, thirst often ___
decreases
K recommendations in 1 and 2:
unrestricted but note DN interactions with ACE 1 and ARB, diuretics
K recommendations stage 3+4
restrict 50-80mmol (2-3g)
why hyperkalemia usually not occur til later stage?
cuz distal tubules have excess capacity to excrete it
adverse effects associated with severe hypokalemia/hyperkalemia?
cardiac arrhythmias
stage 1 and 2 recommendations for Ca:
aim for DRI, unrestricted (but discuss added P)
stage 3+4 recommendations for Ca:
Ca avoid/treat symptomatic hypocalcemia <2000mg–>prevent bone loss
patients at risk of deficiencies cuz:
poor intake, diet restriction, losses in dialysate
at stage 4 recommend this:
a multivitamin supplement for water soluble vitamins
why avoid supplemental vitamins A and C?
prevent toxicity–>transport protein probs so vit A accumulates; vit C increases oxalate formation (Ca-oxalate kidney stones)
why ^ protein intake in end stage on dialysis?
dialysis assists getting rid of metabolic end products, plus some extra protein losses (loss in the dialysate, accelerated protein catabolism due to dialysis)
fluid recommendation for stage 5
1-1.5 L
____ body weight is most useful for assessing nutrition status
post dialysis
energy needs with peritoneal change cuz:
significant absorption of glucose from dialysate as source of energy (subtract energy obtained from glucose in equations for estimate energy needs)
Phosphorus recommendation at stage 3:
800-1000 mg ideal, up to 1200mg P, think of malnutrition (protein, meat)
control of water excretion is regulated by:
vasopressin (antidiuretic hormone)
normal waste products?
urea, uric acid, creatinine, ammonia
if normal waste products are not eliminated properly they collect in abnormal quantities in blood, known as:
azotemia
what is the renin-angiotensin mechanism?
reg blood pressure: decreased blood volume causes cells of the glomerulus to react by secreting renin (proteolytic enzyme)–>acts on angiotensinogen in plasma to form angiotensin 1–>angiotensin 2–>vasoconstrictor and potent stimulus of aldosterone secretion by the adrenal gland–>sodium and fluid reabsorbed, BP returned normal
role of kidney on bone?
produces active vitamin D, eliminates Ca and P
single most important risk factor for all types of kidney stones (nephrolithiasis)?
low urine volume
leading cause of CKD?
diabetes (followed by hypertension and glomerulonephritis)
markers of stage 1 and 2?
proteinuria, hematuria, anatomic issues
primary goals of nutrition therapy in CKD?
manage symptoms, decrease risk of renal failure, decrease inflammation, maintain nutrition stores
clinical syndrome of malaise, weakness, nausea, vomiting, muscle cramps, itching, metallic taste, near impairment cuz of unacceptable lvl of nitro wastes in body
uremia
waste products and electrolytes move by _________ from the blood into dialysate and are removed
diffusion, ultrafiltration, osmosis
method for evaluating efficacy of dialysis, measuring removal of urea from pt blood over given period
kinetic modeling
method to determine effectiveness dialysis tratment that looks at the reduction in urea before and after dialysis
urea reduction ratio
6 goals of nutrition therapy in management of end stage renal disease:
prevent deficiency and maintain good nutrition status, control edema and electrolyte imbalance, prevent development of renal osteodystrophy, enable palatable and attractive diet, coordinate patient care, provide education counselling and monitoring
pt should not take oral iron at the same time as:
phosphate binders
limit fruits/veg and juices to ___ servings/day, limit dairy products to ____ serving/day
6;1
strategies to deal with thirst without drinking:
sucking on ice chips, cold sliced fruit, sour candies, artificial saliva
why over secretion of PTH?
cuz lack of active vit D means poor GI absorption of Ca, plus Ca needs ^ cuz serum P ^–>hypertrophy of parathyroid gland
this occurs when calcium phosphate removed from bones is deposited in non bone cells, when serum Ca and serum P multiplied together = > 70
metastatic calcification
this occurs when calcium phosphate is deposited in wound tissues with resultant vascular calcification, thrombosis, non healing wounds, gangrene
calciphylaxis
all people taking EPO need:
periodic IV or intramuscular iron
why niacin helpful lowering phosphate lvls in ESRD?
interferes with Na-PO4 pump in GI lumen, cause decreased transport of phosphate
why high serum glucose cause hyperkalemia?
water and potassium pulled out of cells
why transplant recipients have elevated serum TG or Cholesterol?
tissue wt gain and resultant obesity, med side effects, lack of physical exercise
most common stage of CKD
stage 3
what causes metabolic acidosis?
primarily from protein (amino acid), low bicarbonate
