Lecture 8 Introduction to Kidney Diseases & Renal Laboratory Tests Flashcards
(19 cards)
What is an acute kidney injury (AKI)?
an acute decrease in kidney fxn or glomerular filtration rate (GFR) over period of hours, days, or even weeks and is associated with accumulation of waste products and (usually) volume
are at risk of developing CKD
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Azotemia
an accumulation in blood of nitrogenous waste products (BUN or creatine)
Hematuria
presence of blood (RBCs) in urine
Pyuria
presence of WBCs or puss in urine,, reflects presence of inflammation more so than infection
Oliguria
reduced urine output defined as approx 100-400 mL in 24 hours
Anura
is < 100 mL of urine in 24 hours
How is glomerular filtration rate used as an ideal marker of kidney fxn?
it cannot be measured directly
ideal marker should be: stable conc in plasma, physiologically inert, freely filtered at glomerulus, not secreted, reabsorbed, synthesized, nor metabolized in kidney
amount secreted at glomerulus is equal to amount excreted in urine
Serum Creatinine (ref range, what it is)
Ref Range: 50-110 umol/L
metabolic by-product of muscle
serum conc primarily determined by pt muscle mass
almost exclusively eliminated by glomerular filtration - 85% filtration, 15% tubular secretion
inverse relationship between this and kidney fxn
What are some things that affects serum creatinine measurements?
affected by: sex, biological sex, weight, malnutrition, muscle wasting, amputation/paralysis
not sensitive measure of kidney fxn, rate of change variable - generally not immediate
What are things that cause decreased and increased creatinine levels?
Decreased: paralysis, low activity level, elderly, decreased muscle mass, cirrhosis
Increased: renal causes, large dietary protein intake, vigorous exercise, increased muscle mass
What is the Cockcroft-Gault equation?
it is a way to measure creatinine clearance
CrCl (ml/min) = ([140-age] x Wt (kg)) / SCr (umol/L) all x 1.2 (males)
decrease in CrCl with age and increase with weight
Differences between CrCl and GFR regarding estimates of renal fxn?
both estimate renal fxn
CrCl - surrogate marker of renal fxn, more often used to determine drug dosages
Estimated GFR - used to stage CKD, reported by lab when creatinine is measured
Blood Nitrogen Urea (ref range, what it is)
Ref Range: 2.9-8.2 mmol/L
conc of nitrogen in serum
dependent on urea production which occurs in liver, glomerular filtration and tubular reabsorption
can be used to monitor hydration, renal fxn, protein tolerance and catabolism, but generally not routinely ordered/used to assess renal fxn
can be used to predict risk of uremic syndrome in pt with severe renal failure
What are things that cause decreases and increases in BUN?
Elevations - high protein diets, upper GI bleeding, dehydration/volume depletion, AKI and CKD
Decrease - may be low in malnutrition or with profound liver damage, fluid overload (dilution)
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What is involved in macroscopic analysis in urinalysis?
General appearance: colour - varies from normally clear to dark yellow or amber, depending on conc of solutes
Turbidity: cloudiness or haziness - can occur if urates or phosphates crystalize or precipitate in urine, large numbers of WBC or RBC present
Foamy appearance: presence of protein or bile acids
What is involved in microscopic analysis in urinalysis?
microorganisms (zero to trace), RBC (1-3/high powered field (HPF)), WBC (0-2/HPF), epithelial cells (0-1/HPF)
Casts - cylindrical masses of glycoproteins that form in tubules, normal = a few clear casts, abnormal = hyaline, cellular casts (WBC, RBC, epithelial), granular casts
crystals (normal = none)
What is involved in chemical analysis in urinalysis?
Urine dipstick - protein (zero to trace), pH (4.6-8), specific gravity (1.010-1.025), bilirubin, leukocyte esterase, nitrite, glucose, ketones
electrolytes - urine sodium (varies), %FeNa - fractional excretion of sodium, potassium (varies)
Urine Protein/Albumin (how to measure, range)
Normally: <100 mg/24 hours, helpful biomarkers to assess progression of CKD
Measures: Urinary Albumin or Protein Excretion Rate (UAER, UPER) - 24 hr urine collection, estimated 24 hr urine excretion using 4 hr timed urine collection, urine dipstick
Albumin:Creatinine ratio (ACR): <2.0 mg/mol - random urine spot test
What are some causes of transient albuminuria?
recent major exercise, UTIs, febrile illness, decompressed congestive HF, menstruation, acute severe elevation in blood glucose, acute severe elevation in BP
