Physical & Chemical Examination of Urine Flashcards
1
Q
Why analyze urines?
A
fluid biopsy of kidney
noninvasive means to evaluate kidney
readily available
urine is ultrafiltrate of plasma
2
Q
First morning specimen
A
most concentrated; often preferred specimen
most acidic- formed elements are better preserved
3
Q
Random specimen
A
for routine screening
can be affected by excess fluid intake or exercise
4
Q
Timed specimen
A
collections for predetermined length of time or at a specific time of day
primarily used for chemistry testing
5
Q
Midstream ‘clean catch’
A
for bacterial cultures or to prevent vaginal contamination
begin urination into toilet, collect midstream portion in container, finish voiding in toilet
6
Q
Catheterized specimen
A
requires collection by medical personnel
sterile catheter insterted through urethra into bladder
7
Q
Suprapubic Aspiration
A
requires collection by medical personnel
involves puncturing of abdominal wall & distended bladder by using needle & syringe
normally sterile
used for cultures or in infants (anaerobic infections)
8
Q
Pediatric collections
A
plastic urine collection bag attached to perineal skin
routine testing
9
Q
Reasons for specimen rejection
A
unlabeled/ mislabeled mismatch of specimen name with order inappropriate collection technique not properly preserved time delay in receipt of specimen visibly contaminated insufficient volume
10
Q
Containers
A
clean, dry, clear, sterile containers
11
Q
preservation of samples
A
preserve specimen if not processed in 2 hours or more
12
Q
pH change after 2 hours at RT
A
increased pH because of the break down of urea into ammonia by bacteria
13
Q
glucose change after 2 hr at RT
A
decreased
glycolysis & bacterial utilization
14
Q
ketone change after 2 hr at RT
A
decreased
volatilization of compounds
15
Q
bilirubin change after 2 hr at RT
A
decreased
exposure to light
16
Q
urobiliogen change after 2 hr at RT
A
decreased bc of oxidation to urobilin
17
Q
nitrite change after 2 hr at RT
A
increased or decreased
bacterial reduction to nitrate or all the way to nitrogen gas
18
Q
bacteria change after 2 hr at RT
A
increased
19
Q
color change after 2 hr at RT
A
varying changes due to oxidation or reduction of metabolites
20
Q
turbidity change after 2 hr at RT
A
increased bc bacterial growth & precipitation of amorphous material
21
Q
sediment change after 2 hr at RT
A
disintegration bc of dilute alkaline urine
22
Q
most common preservation technique for urines
A
REFRIGERATION!!
should not be used for routine testing if urine will be analyzed within 2 hr
23
Q
other urine preservatives
A
10% formalin
thymol/toluol
boric acid
NaF
24
Q
urine color
A
due to the presence of urochrome- by product of bilirubin
25
foam
not normally included on report forms
stable white foam indicates large amounts of albumin
yellow foam is increased bilirubin
26
causes of cloudiness
contamination from skin, vaginal secretions, bacterial growth or fecal material
precipitation of dissolved solutes, x-ray contrast media
RBCs, WBCs, clots, casts
27
normal daily volume
600-1800 ml/day
28
polyuria
>3L per day of urine
29
oliguria
<400 mL per day
30
anuria
0 mL per day
31
nocturia
>500 mL at night
| highly suggestive of chronic progressive renal failure
32
odor
normally has aromatic odor
| urine on standing becomes more odorous due to bacterial conversion of urea to ammonia
33
Specific gravity
an expression of concentration in terms of density: mass of solutes present per volume of solution
1.002-1.040
read via refractometry & reagent strip chemical method
34
3 factors that affect the refractive index of a solution
wavelength of light used
temperature of solution
concentration of solution
35
Specific Gravity strip test principle
indirect measurement
strip pad impregnated with a polyelectrolyte & a pH indicator at an alkaline pH
protons are released from polyelectrolyet in proportion to ionic concentration of the urine; released protons change pH of test pad
36
False decrease of Specific gravity test
high glucose & urea concentrations
| pH >6.5
37
false increase of specific gravity test
high protein & ketoacids
| X-RAY CONTRAST MEDIA - will make it so elevated that the urine will need to be diluted
38
pH of urine & clinical significance
4.5-8.0
| precipitation of crystals, treatment of UTI, determination of poor specimen
39
pH principle
two indicators: METHYL RED & BROMTHYMOL BLUE
40
Protein general
indicative of renal disease
| normal excretion <150mg/day (threshold of dipstick)
41
components of urine protein
albumin! -1/3
microglobulins
Tamm-Horsfall (uromodulin)- protein synthesized by distal convoluted tubule & in cast formation
proteins from fluids
42
orthostatic proteinuria
excreting protein during the day/moving & not excreting while laying down/not moving
43
pathological proteinurias
Multiple myeloma- bence jones
glomerular membrane damage
impaired tubular reabsorption
microabluminuria - DIABETIC PATIENTS; this will monitor kidney function
44
transient proteinuria
benign, exercise, goes away after period of rest
45
#1 cause of acute glomerular nephritis
strep throat (group A strep)
46
precipitation protein test
3% sulfosalicyclic acid (SSA)- equal parts SSA & urine supernatant
47
false positives on SSA protein test
X-RAY CONTRAST MEDIA!
| high doses of penicillin
48
false negatives on SSA protein test
highly buffered (alkaline) urine
49
Dipstick protein principle
colorimetric albumin test:
'protein error of indicators'- pad w/ pH indicator
H+ combine with protein causing a color change
50
false positives of dipstick protein
```
highly alkaline (buffered) urine
urine in contact w/ strip for prolonged time
detergents
```
51
false negatives of dipstick protein
protein other than albumin present
| substances that mask color
52
Microalbumin
routine test strips unable to detect albumin in urine that is <1-2 mg/dL
most often used in patients with diabetes to screen for kidney damage
53
Glucose
used as a screening test for diabetes
| renal threshold - 160 +/- 20 mg/dL
54
classic picture of diabetic urine
```
low pH
dilute
pale yellow
high specific gravity
high glucose
```
55
high urine glucose & normal plasma glucose
pregnancy
emotional stress
diet high in COH
56
dipstick glucose test
glucose oxidase- principle based on double sequential enzyme reaction that is specific for only glucose
glucose oxidase- oxidizes glucose for form H2O2
peroxidase- H2O2 to oxidized chromogen resulting in color change
57
false positives of dipstick glucose
```
oxidizing agents (ppl using bleached containers for their urine)
peroxidase contaminants
```
58
Copper reduction test
detects all reducing sugars (sucrose only non reducing sugar)
clinitest- should be performed on all children to test for inability to metabolize galactose
59
Ketones in urine
breakdown products from large amounts of fatty acids
| diabetic ketoacidosis or excessive CHO loss - low CHO diet, vomiting, diarrhea, eating disorders
60
ketone dipstick test
nitroprusside reaction
| in alkaline medium, acetoacetate reacts with sodium nitroprusside in pad causing color change
61
false positives for ketone dipstick
highly pigmented urine, free sulfhydral groups, levodopa metabolites
62
false negatives for ketone dipstick
improper storage
| ketone bodies are volatile & will evaporate
63
hematuria clinical significance
whole RBC in urine
pre-renal
renal- glomerular nephritis
post renal- kidney stones
64
hemoglobinuria clinical significance
lysed RBC in urine
exogenous- burns, trauma, drugs
endogenous - hemolytic anemias etc
65
myoglobinuria clinical significance
muscle hemoglobin in urine
muscle wasting diseases
severe exercise
66
blood dipstick test
'heme's pseudoperoxidase activity'
| pad has chromogen & peroxide, pseudoperoxidase reduces peroxide & chromogen is oxidized causing color change
67
tips for testing blood in urine
always ensure urines are well mixed as RBCs will settle out
| RBCs lyse in an alkaline urine
68
false positives for blood dipstick
oxidizing agents
microbial peroxidases
menstrual contamination
69
false negatives for blood dipstick
ASCORBIC ACID, high specific gravity
captopril
RBCs settle out
70
hematuria color, chemical & microscopic
red, smokey
positive dipstick
positive microscopic
71
hemoglobinuria color, chemical & microscope
pink, red, brown & clear
positive dipstick
negative microscope
72
myoglobinuria color, chemical & microscope
brown & clear
positive dipstick
negative microscope
73
Solubility test
myoglobin is soluble in ammonium sulfide while hemoglobin is not
differentiates myglobinuria vs hemoglobinuria
74
bilirubin production
prehepatic jaundice- hemolytic anemia & transfusion rxns
hepatic jaundice- hepatitis & cirrhosis
post hepatic jaundice- obstructive jaundice from stones or tumors
75
prehepatic urine bilirubin & urobilinogen
urine bilirubin- negative
| urine urobilinogen - increased
76
hepatic urine bilirubin & urobilinogen
u. bilirubin- positive
| u. urobilinogen- increased
77
hepatic (unconj.) urine bilirubin & urobilinogen
u. bilirubin - negative
| u. urobilinogen - normal or decreased
78
post hepatic urine bilirubin & urobilinogen
u. bilirubin - positive
| u. urobilingoen - negative!
79
dipstick test for bilirubin
diazo reaction
| bilirubin reacts with diazonium salt in pad to form azobilirubin which is brown
80
false positives for dipstick bilirubin
drugs
| urine pigments
81
false negatives for dipstick bilirubin
ASCORBIC ACID
high nitrate
improper storage
82
icotest
more sensitive test for bilirubin
| washes away pigments in urine
83
best specimen for urobilinogen
2 hr collection from 2-4 pm during 'alkaline tide'
84
urobilinogen dipstick principle
ehrlich's reaction
P-dimethylaminobenzaldehyde: reacts with urobilinogen & porphobilinogen
can NOT detect a decreased urobilinogen
85
false positives for urobilinogen
other ehrlich reactive compounds: atypical colors or substances that mask results
86
false negatives for urobilinogen dipstick
formalin
| improper storage
87
Watson-Schwartz differentiation
urobilinogen is soluble in organic solvents (chloroform & butanol)
porphobilinogen is insoluble in organic solvents & stay in the urine
88
nitrite intro & clinical significance
```
rapid screen for UTI test
cystitis- bladder infection
pyelonephritis - kidney infection
evaluation of effectiveness of antibiotic therapy
screen for urine cultures
```
89
nitrite dipstick test
diazotization reaction of nitrite with an aromatic amine in pad:
forms a diazonium salt which couuples with an aromatic compound in pad to produce azo dye
color change to white to pink
90
false positives of nitrite test
increase in bilirubin or other pigment
| improper storage
91
false negatives of nitrite test
```
ASCORBIC ACID
antibiotics
non-nitrate reducing bacteria
urine not in bladder long enough
urine does not contain nitrate
```
92
Leukocytes intro & clinical significance
UTIs, cystitis or pyelonephritis
| only picks up WBCs with esterases - NOT LYMPHS
93
leukocyte dipstick test
principle based on action of leukocyte esterase to cleave an ester in pad
94
false positives leukocyte dipstick
substances that induce color or mask results
| vaginal contamination
95
false negatives leukocyte dipstick
```
high levels of glucose & protein
LYMPHS present
high specific gravity
strong oxidizing reagents
drugs
```
96
Ascorbic acid
interferes with : glucose, blood, bilirubin, nitrite & leukocytes
