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Nephrology > Lab Assessments > Flashcards

Lab Assessments Flashcards

1
Q

4 major functions of the nephron are?

A
  1. Filtration
  2. reabsorption
  3. secretion
  4. excretion
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2
Q

movement of water and solutes from the bloodstream to the renal tubule (nephron)

  • glomerulus
  • 20% of plasma volume passing through is filtered
  • drive by hydraulic pressure
A

Filtration

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3
Q

movement of water and solutes from the renal tubule back into the blood stream

  • throughout the renal tubule
A

reabsorption

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4
Q

movement of additional substances from the bloodstream into the renal tubule

  • helps with the elimination of wastes
  • helps maintain K balance
  • helps maintain pH
A

Secretion

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5
Q

total substance removed in urine

  • = filtration-reabsorption + secretion
A

Exretion

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6
Q

sum filtration rate of all the functioning nephrons

  • gold standard for measuring kidney function
  • normal = 120/ml/min
  • varies according to age- decreases every 10 years after age 40, gender, body size
A

GFR

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7
Q

uses of GFR?

A
  • identify kidney disease/disorders
  • selection of medication dosages
  • avoidance of certain medications (nephrotoxic i.e, NSAIDS, antibiotics, antifungals)
  • monitior CKD (chronic kidney disease)
  • criteria for referral and dialysis
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8
Q

what are GFR levels? when should you refer, when should they be on dialysis?

A
  • Normal GFR > 90
  • CKD2 (mild) = 60-89
  • CKD3 (moderate) = 30-59 (REFER)
  • CKD4 (severe) =15-29
  • CKD5 failure) = < 15 (DIALYSIS)
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9
Q
  • Produced as the result of normal muscle metabolism
  • a product of skeletal muscle contration (dependent on muscle mass of patient)
  • excreted entirely by kidney (directly proportional to renal exretory function)
  • used to approximate the glomerular filtration rate
  • normal serum levels is 0.5-1.5mg/dL
A

creatinine

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10
Q

what is the relationship beetween serum creatinine and GFR?

A

Inverse relationship between serum creatinine

  • 2x increase in CR = GFR decrease by 50%
  • mild elvation = significant dysfunction
  • this applies even when values remain within normal limits
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11
Q
  • measure of GFR
  • normal - 100mL/min (Dependent on age and gender)
  • calculated by two means: directly, indirectly
A

Creatinine clearance

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12
Q

how do you measure CrCL directly?

A

24 hour urine collection

  • both serum and urine needed
  • collection does not provide more accurate estimate of GFR than do prediction equations
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13
Q

how do you measure CrCl indirectly?

A
  • uses serum creatinine in
  • the cockroft-gault equation
  • pharmacokinetic studies use eCrCL therefore it has become the standard for drug dosing
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14
Q

It is is produced in the liver, found in blood and is secreted and reabsorbed by the kidneys

  • directly related to the metabolic function of liver
  • assuming normal liver function it is an estimate of renal functions
  • other variables that effect?- protein breakdown, hydration status, liver failure
  • rises quickly in dehydration (faster than CR)
A

Blood urea Nitrogen

(5-26) mg/dL

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14
Q

increase in nitrogenous waste products (urea and creatinine) diagnosis made on labs alone

A

Azotemia

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15
Q

symptomatic azotemia (N/V, lethargy)

A

uremia

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16
Q

classify the duration of kidney failure?

A
  • acute= less than 3 months duration
  • chronic= greater than 3 months duration
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17
Q
  • good screening test for obstruction and to differentiate acute vs chronic renal disease
  • can alo obtain additional information: cysts, the renal size disparity
A

Renal ultrasound

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18
Q

ways to find the cause of kidney failure?

A
  • Bun/cr ratio
  • urine Na
  • fractional excretion Na
  • urine Sp Gr
  • urine osmolality
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19
Q

Evaluate BUN/Cr ratio levels and kidney function

A

> 20:1 = pre-renal

  • GI bleed
  • decreased volume
  • urine obstruction

< 20:1

  • Intra-renal
  • often chronic (CKD)
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20
Q
  • Compare to serum
  • sodium and potassium most common
  • random urine Na < 10 suggests dehydration (CHF, liver disease)
  • randome urine Na > 20 suggest kidney/adrenal disease
  • can be used to calculate FENa (an equation that is helpful to distinguish between pre-renal and intra-renal azotemia)
A

Urine electrolytes

21
Q
  • Both reflect the kidney’s ability to concentrate urine and relative hydration
  • typically specific gravity varies with osmolality
  • determined by the number of particles in the urine so:
  • higher with dehydration
  • lower with hydration
A

urine specific gravity and osmolality

mainly used for hydration status

21
Q
  • Could be hematuria, hemoglobinuria, myoglobinurina
  • presence of erythrocytes on microscope confirms
  • false positive is common therefore confirm with microscopy
  • false negative is uncommon
A

Blood (urinalysis)

22
Q

What is evaluated in a gross evaulation of urine?

A

color:

  • normal varies, influenced by chemical compisition, urine concentration
  • can be red- hematuria, food dyes, beets, medications (rifampin)
  • red to brown- hemoglobinuria (hemolytic anemia) myoglobinuria (rhabdomyolysis)
  • orange- vitamin C, carrots, medications
  • green- dyes (Methylene blue), medications(propfol) asparugs

clarity

  • clear = norma
  • cloudy= “gray area” - coul be normal (precipitated phophate crystals in the urine, could be pyruia (pus/bacterial infection)
  • turbid= infection, crystals, protein, etc

Odor

  • Urinoid= normal
  • pungent may –> UTI
  • Fruity/sweet = DKA
  • fecal–> Fistula
23
Q

causes of Acidic pH?

A
  • uncontrolled DM
  • starvation
  • dehydration
  • diet: protein and acidic fruits
24
Q

causes of alkaline pH?

A
  • salicylate intoxication
  • chronic renal failure
  • proteus infection
25
Q

the hallmark of renal disease
two barriers: basement membrane pores and basement membrane negative charge

A

Proteinuria

26
Q

Proteinuria classifications?

A

Transient

  • causes?
  • temporary change in glomerular hemodynamics causes the protein excess
  • follows a benign, self-limited

persistent

  • further classifed into 3 categories
27
Q

persistent proteinuria classification

A

Glomerular

  • may cause MASSIVE proteinuria
  • albumin is the primary protein
  • many etiologies

Tubular

  • malfunctioning tubule cells no longer metabolize or reabsorb the normally filtered protein
  • low molecular weight proteins predominate
  • rarely exceed 2g/day

overflow

  • low-molecular weight proteins overwhelm the ability of the tubules to reaborb filtered proteins
28
Q

What should be done with asymptomatic patient with mild proteinuria dip?

What about proteinuria on anyone else

A

if all else is normal on dip

  • recheck the urine dipstick
  • transient proteinuria is common esp. with fever, exercise, hypothermia, stress, pregnancy, seizure

Anyone else

  • get a 24 hour urine
  • microscopic examination of the urinary sediment
  • urinary protein electrophoresis
  • assessment of renal function
  • < 3g/24 hours== glomerular or tubular disease (nephrotic)
  • > 3g/24h== nephrotic range proteinuria typically GLOMERULAR
29
Q
  • Excretion of 30-150 mg of protein/day
  • not detectable by normal urine dip methods, so is a separate test
  • affected by hydration status
  • indicated by renal tubular disease
A

Microalbuminuria

30
Q
  • normally filtered by glomerulus and reabsorbed by proximal tubule
  • present in urine when load exceeds ability of renal tubule to reabsorb
  • sign of DM, cushing’s, liver and pancreatic disease
A

Glucose

31
Q
  • should not be present on UA
  • products of fat metabolism
  • may be exepected in: diabetes, starvation, strenous exercise, frequent vomiting, low carb diets, pregnancy
A

Ketones

32
Q
  • converted by certain bacteria
  • this test is specific but not very sensitive (+ result confirms the diagnosis of UTI, (-) result does not rule it out
  • bacteria may still be present in the absence
  • portion of the stick is sensitive to air
A

nitrites

33
Q
  • WBC in urine undergo lysis and esterases are released
  • maker of the presence of WBCs in urine= pyruia
  • sign of UTI
A

Leukocyte esterase

34
Q
  • could be hematuria, hemoglobinuria, myoglobinuria
  • presence of erythrocytes on microscoope confirms blood as cause
  • 3+ RBC/HPF in 2 of 3 urine samples
  • false positive is common therefore confirm with microscopy
  • false negative is common
A

Blood

35
Q

what microscopic cells can be seen on urinalysis and what does that indicate?

A

Squamous epithelial cells

  • > 15-20 cells/ hpf
  • usually indicates the urine is contaminated

Transitional epithelial cells

  • can be normal (bladder, proximal urethra, renal pelvis)
  • larger amounts may be suggestive of UTI

Tubular epithelial cells

  • desquamation of the tubular epithelium
  • suggests significant renal pathology
36
Q
  • indicates infection
  • > 100,000/mL reflects significant bacteriuria in an asymptomatic patient
  • in symptomatic patient > 100/ml suggest UTI
  • the diagnosis should be followed by culture and sensitivity
A

Bacteria

37
Q
  • Coagulum of protein and the contents of the tubule in which they form
  • factors that promote formation: Low urine flow rate, high urinary concentration, low urine pH
  • cellular elements determine the type of cast and can hint to certain disease processes
  • generally considered a significant finding
A

Casts

38
Q
  • small #s with exercise, dehydration, stress, pyelonephritis
  • may be a normal finding
  • from the distal tubules
  • protein without cellular inclusion
A

Hyaline casts

39
Q
  • # of casts increase with severity of disease
  • indicated glomerulonephritis: inflammation leads to damage of basement membrane which leads to sudden onset of hematuria, proteinuria, and RBC casts
A

Erythrocyte (RBC) cast

40
Q
  • Made with WBCs

infectious or inflammatory conditions

  • UTI
  • Interstitial nephritis
  • pyelonephritis
  • glomerulonephritis
  • renal inflammatory processes
A

Leukocyte cast

41
Q
  • Seen with renal tubule disease (dilation and destruction of tubules)
  • cellular components, if present, are mixed and may include renal tubular epithelial
  • seen in ATN, interstial nephritis, eclampsia, nephritic syndrome
A

Epithelial

42
Q
  • made up of various cell types in final phase of cellular degeneration
  • very slow tubular transit time
  • severe chronic renal disease (HTN nephropathy)
A

Waxy/granular cast

43
Q
  • lipid laden renal tubule cells
  • indicated nephrotic syndrome, renal disease, hypothyroidsim
A

Fatty cast

44
Q

made of various cell types
indicate end-stage renal disease

A

Broad cast

45
Q
  • square envelop shape
  • vary in size
  • common with stones
A

calcium oxalate

46
Q
  • yellow-orange brown in color
  • diamond or barrel shaped
  • common with gout
A

uric acid

47
Q
  • may be normal finding
  • associated with alkaline urine and UTI
  • colorless
  • “coffin lid” appearance
A

Triple phosphate

48
Q
  • colorless
  • heagonal shape
  • acidic urine
  • diagnostic of cystinuria
A

Cystine crystals

Nephrology (12 decks)

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