4 - Lab Testing Flashcards
1
Q
He said
A
This stuff is high yield, maybe focus a little more on it
But i’m not your mom do what you want
2
Q
Pt evals for suspected renal disease must include (at a min):
A
- H/P
- UA w dipstick/microscope
- BUN and
- serum creatinine
- assessment of GFR
3
Q
UA is aka?
A
Poor man’s renal biopsy
4
Q
Urine is assessed for?
A
Assessed for:
- Apperance
- chemical test (dipstick)
- microscopic exam
5
Q
Preferred collection method?
A
Clean catch, midstream sample
6
Q
What does the exam of the urine sediment tell you?
A
Valuable clues about renal parenchyma
7
Q
Apperiance factors for urine?
A
Color
Clarity
Odor
8
Q
Urine color indicates?
A
Normally clear-dark yellow
Color darkens
- H concentration (dehydration)
- myoglobinuria
- bilirubinuria
- kidney disease
Color changes:
- orange: phhenazopyrieind, nitrofurantoin, rifampin, metrnidazol
- pink: hemolysis
Pic on slide 11
9
Q
Clarity values?
A
- cloudy -> pyruia and suspended crystals
- alkaline urine
10
Q
Examples of normal results and dipstick pics?
A
Slides 12-16
11
Q
What is leukocyte esterase?
A
An enzyme produced by neutrophils
POS: WBCs in urine
12
Q
False pos/neg for leukocyte esterase?
A
False pos: contamination
False neg: glycosuria, concentrated urine, drugs, not waiting long enough for testing
13
Q
What causes nitrites?
A
Many gram-neg bacteria (esp e. Coli) can reduce nitrate to nitrite
1st morning void is best
14
Q
Positive nitrite?
A
Bacterial infection
- neg doesnt r/o bacterial infection
15
Q
Trace protein =
A
= 150mg
16
Q
Protein indicates?
A
Usually 1st indication of renal disease
Mostly albumin on dipsticks
17
Q
Normal pH?
A
- 0-6.0 - 1st morning sample
- 5-8.0 - random samples
The dipstick shows 5.0-8.5 so random is basically useless
18
Q
Urinary pH is useful in the diagnosis of?
A
UTIs
Urinary stone
Disease
Renal tubular acidosis
19
Q
Blood is 7.4ish so how does urine get more acidic?
A
Glomerular filtrate enters the tubule at normal physiologic pH (7.4) and acidifies in the DCT and collecting duct
20
Q
What does the blood square measure?
A
Intact erythrocytes
Free hemoglobin
Myoglobin
21
Q
False pos/neg blood?
A
False pos: menses, concentrated urine
False neg: high ascorbic acid
22
Q
Normal specific gravity?
A
1.005-1.030
23
Q
Spec gives indication of?
A
Insight into
- urine osmolality
- dehydration and shock (high)
- overhydration or impaired ability to concentrate (lower)
24
Q
Ketones
A
Detects acetic acid
25
Normal urobilinogen?
0.2-1.0mg/dL
| (Shows as “normal” on the dipstick
26
Where does urobilinogen come from?
Formed in intestinal tract by bacterial breakdown
of conjugated bilirubin
– 50% reabsorbed into portal circulation & reprocessed
by liver
– small amount is normally excreted in urine
– majority is excreted via feces
27
High urobilinogen suggest?
Hemolysis
Hepatocellular disease
- hepatitis and cirrhosis
28
If you still dont understand the bili process
Slide 32 has a pic
| Cant hurt its only been taught 5-6 times maybe this time itll stick
29
High bilirubin in serum (bilirubinemia) leads to:
Bilirubinuria (bilirubin in the urine)(normally urine should have NO bilirubin)
Suggest hepatocellular disease
- liver can’t clear conjugated bili
- cirrhosis or hepatitis
30
Normal glucose?
<0.1% (below the sensitivity level of UA dipstick)
31
How is the microscopic analyses processed?
Centrifuged urine sediment exam under microscope
You must request “micro”
32
What is “significant” level of erythrocytes?
>3 RBCs per HPF (high power field)
The need a further workup
33
RBC appearance/morphology?
Round/normal: disease in epithelial tract
Dysmorphic: (irregular) nephrotic syndrome
Creanated (shrunken/scalloped) concentrated urine
Cell ghosts: swollen RBCs due to dilute urine
Regular ghosts: paranormal infection
34
Presence of leukocytes (microscopic)
Pyuria
>5 leukocytes per HPF
35
Leukocyte findings?
Neutorphils - bacteria
Eosinophils - allergic interstitial nephritis
Pyuria - UT injury
36
sterile pyuria?
WBC present but neg culture
37
Other causes of pyuria?
```
– Stones
– Strictures
– Neoplasm
– GU tuberculosis
– Glomerulonephropathy
– Interstitial nephritis
```
38
Epithelial cell findings?
Squamous epithelial - contamination
Transitional (urothelial cells)
- normal (maybe)
- neoplasm
39
Renal tubular epithelial cells?
Clinically relevant
Diagnostic for ischemic/nephrotic acute tubular necrosis (ATN)
40
Casts are?
Formed in distal convoluted tubules (DCTs) and collecting ducts
Named by shape and origin
41
Casts suggest?
Renal parenchymal disease
42
red cell casts?
Bleeding
Hallmark of glomerulonephritis
43
White cell casts
Acute pyelonephritis
- also seen in acute interstitial nephritis (eosinophils)
Useful in distinguishing acute pyelonephritis from lower tract infection
44
Renal tubular epithelial cell casts
Sloughed tubular cells -> acute tubular necrosis (ATN)
45
Granular casts
Aka muddy brown casts
degenerating cells of various origins
- nonspecific but pathologic
- ATN maybe
46
Waxy casts
Severe urine stasis in renal tubules
| - chronic renal failure
47
Broad casts?
Tubules are dilated and atrophic
- chronic parenchymal disease
- severe urinary stasis
- ESR failure
48
Fatty casts?
Numerous renal disease
| - esp nephrotic syndrome
49
Hyaline casts
Associated w/
- concentrated urine
- febrile disease
- strenuous exe
- diuretic therapy
Not specific
50
Urine crystals formation depends on?
- concentration
- urine pH
- presence/absence of crystallization inhibitors
51
Crystal types?
```
– Uric Acid
– Calcium phosphate & Oxalate
– Cystine → hereditary cystinuria
– Struvite → “infection stones”; urease producing
organisms such as Proteus or Klebsiella
```
52
Bacteria in urine is called?
Bacteriuria
Get a culture
53
MC yeast in urine?
Candida albicans
54
Yeast is common in?
```
– Elderly (esp., female)
– Antibiotic use
– Diabetes
– Catheter use
– Post-surgery
```
Buds and hyphae
55
Trichomonas looks like?
Pear shaped
| Flagellated
56
Urine culture is ordered if?
Cases of suspected UTI or pyelonephritis
Not necessarily a reflexive order
57
Example CMP, BMP report?
Slides 58,59
58
What is urea?
End product of protein catabolism
Excreted principally by glomerular filtration
59
Serum marker of urea level?
BUN (blood urea nitrogen)
60
Normal BUN?
5-20 mg/dL
61
BUN increase w/:
- acute/chronic renal failure
- obstruction/stone
- dehydration
62
Increased BUN?
```
• Dehydration
• Reduced renal perfusion (congestive heart failure, hypovolemia)
• ↑ dietary protein
• Accelerated catabolism
(fever, trauma, GI bleeding)
• Steroids
• Tetracycline
```
63
Decreased BUN?
• Over-hydration
• ↑ renal perfusion
(pregnancy, SIADH)
• Restriction of dietary protein/malnutrition
• Liver disease (impaired metabolism of ammonia to
urea)
64
What is serum creatinine (Scr)
Normal 0.5-1.2 mg/dL
Product of muscle metabolism
A means of estimating GFR
65
Serum creatinine is excreted by?
Glomerular filtration - 90-05%
Distal tubule - 5-10%
66
Serum creatinine is increased by?
```
• acute or chronic renal
failure
• urinary tract obstruction
• ↑ cooked meat intake
• ↑ muscle mass
• meds (i.e., cephalosporins, cimetidine, probenecid, & trimethoprim)
– +/- creatine supplementation
```
67
Serum creatinine is decreased by?
* vegetarian diet
* ↓ muscle mass (small children, elderly)
* drugs (i.e., methyldopa)
68
Normal BUN: Creatinine ratio
10:1
69
Increased/decreased creatinine ratio?
Increased: prerenal and postrenal azotemia
- dehydration
Decrease: intrinsic renal disease
70
Homeostasis and GFR?
Homeostasis of body fluids requires kidneys to maintain relatively constant GFR
71
GFR depends on?
- Renal autoregulation
- neural regulation
- hormonal regulation
72
Regulation mechanisms of GFR?
2 main mechanisms
1. control of blood flow in and out of glomerulus
- changing diameter of afferent and efferent arterioles
2. Control of glomerular surface area
- via contraction or relaxation of mesangial cells
73
Most important parameter in clinical eval of renal function?
GFR
74
Factors that affect GFR?
Body size
Age
Physiologic state
Race
Huge variations
75
GFR is used to?
Adjust medications
76
How is GFR measured?
Measuring the plasma concentration and excretion of a marker substance
- Gold standard - injected inulin, measure
- now its creatinine clearance
77
Cockcroft and gault GFR?
Used to estimate GFR w/out 24-hr urine collection
- serum only
There is a formula slide 72
78
Modification of diet in renal disease (MDRD)
New method to calculate GFR
Dont memorize it
79
FE(na)
Fractional excretion of sodium
- Na excreted by body relative to amount filtered by kidneys
( na remaining in urine)
Most accurate when pt is oliguric
80
What is FE(na) used for?
Suspected acute renal failure (ARF)
81
How to calculate Fe(na)
Slide 76
82
Determine the general cause of AFR?
Decreased perfusion
- FE(na) <1%
- hypovolemia, dehdration
Intrinsic renal disease
- FE(na) >1%
83
How do you cook kidneys?
You boil the piss out of them!
