Urinalysis Flashcards
(71 cards)
1
Q
What are 5 things that can cause urine to be turbid?
A
- crystals
- cells
- bacteria
- protein
- sperm
2
Q
What are the 10 components on a dipstick?
A
- pH
- Specific gravity
- blood
- protein
- glucose
- ketones
- nitrite
- leukocyte esterase
- bilirubin
- urobilinogen
3
Q
What is a normal urine pH?
A
4.5-8
4
Q
What happens to urine pH if it isn’t properly stored/stored for too long?
A
becomes more alkaline
5
Q
What are 3 causes of acidic urine?
A
- high protein diet
- metabolic acidosis
- respiratory acidosis
6
Q
What are 5 causes of alkaline urine?
A
- vegetarian or high citrus diet
- metabolic alkalosis
- respiratory alkalosis
- renal tubular acidosis
- Urinary tract infection (from NH3 production)
7
Q
What is the urine specific gravity a measure of?
A
density of the urine compared to distilled water
8
Q
What is the normal range of USG?
A
1.003 (very dilute) to 1.035 (very concentrated)
9
Q
What 3 things can cause a lower SG (<1.010)?
A
- increased fluid intake
- diuretic use
- diabetes insipidus
10
Q
What 3 things can cause a high SG (>1.030)?
A
- dehydration
- decreased renal perfusion
- SIADH
11
Q
What causes a fixed SG? (1.010)
A
severe renal disease leading to loss of concentrating/diluting ability
12
Q
What does the dipstick test detect in terms of blood products? What confirmatory test do you need and why?
A
Detects peroxidase activity of RBCs
Myoglobin and hemoglobin will also give a + result so you need to confirm with microscopy
13
Q
What can cause a false negative blood result on a dipstick?
A
high levels of vitamin C
14
Q
What is a normal level of urinary protein excretion?
A
<150mg/day
15
Q
What is specifically being detected on the dipstick protein analysis?
A
Mostly is sensitive to albumin so mainly reflects glomerular proteinuria
- not sensitive to other proteins like tubular or Igs
16
Q
How is proteinuria graded?
A
Trace to 4+ and is highly dependent on urine concentration
- dilute urine can underestimate proteinuria and vice versa
17
Q
What cutoff of plamsa glucose is helpful in determining the cause of glucose in the urine?
A
10mM
- > = diabetes
- < = defect in reabsorption of glucose (Fanconi syndrome)
18
Q
What 3 conditions can cause ketones to be present in the urine?
A
- DKA
- alcoholic ketoacidosis
- starvation
19
Q
Which ketone products is detected on dipstick?
A
acetoacetate/acetone
20
Q
Why would nitrite be present in the urine?
A
Nitrate converted to nitrite by bacterial nitrate reductase
= bacterial infection
21
Q
What can cause a false positive nitrite in the urine?
A
- bacterial contamination of the sample
- delayed analysis
- improperly stored dipstick strips
22
Q
What can cause a false negative nitrite?
A
- low nitrate diet
- insufficient urine dwell time in the bladder
- Abx use
- certain bacteria don’t form nitrite (enterococci, streptococci, staph, pseudomonas)
23
Q
What is leukocyte esterase?
A
enzyme found in neutrophils and macrophages
24
Q
What does a positive LE test mean?
A
Presence of intact or lysed WBCs
- infection
- inflammation
- malignancy
- stones
- glomerulonephritis
25
What 3 things can cause a false negative LE test?
high urine protein, glucose, or vitamin C
26
When is urine microscopy ordered?
When you have atypical dipstick results or if the macroscopic exam of the urine looks abnormal
27
What is a normal RBC count on microscopy?
<3 RBC/HPF
28
What causes crenation of RBCs?
hypertonic urine drawing water out and causing deformities
29
What should be suspected if you see dysmorphic RBCs on microscopy?
glomerulonephritis
30
What is a normal WBC count on microscopy?
<5 WBCs/HPF
31
What is the predominant WBC type found in urine?
neutrophils
32
What do eosinophils in the urine suggest?
acute interstitial nephritis
| - used to be pathognomonic but there are other causes like chronic pyelonephritis, prostatitis, and glomerulonephritis
33
What do renal tubular epithelial cells look like on microscopy?
variable shape; round/oval/columnar
all have a well defined round or oval nucleus
34
What causes an increase in renal tubular epithelial cells in urine?
Tubular damage
- ATN
- AIN
- kidney graft rejection
- glomerulonephritis
35
What are oval fat bodies?
Renal tubular epithelial cells or macrophages that are packed with lipid droplets
36
What do oval fat droplets look like and when are they seen?
Have a characteristic "maltese cross" appearance under polarized light
Seen in nephrotic syndrome and some lipid storage disorders
37
Where are transitional epithelial cells found?
From the renal pelvis to the proximal urethra
38
When do you see superficial transitional epithelial cells in the urine?
Inflammatory or malignant disease of the lower urinary tract
39
Differentiate between the morphology of superficial and deep transitional epithelial cells
Superficial: large, circular, small central nucleus
Deep: smaller, oval/club shaped with a large nucleus
40
When would you see deep transitional epithelial cells?
associated with bladder cancer, stones, and hydronephrosis
41
What is the largest cell type found in the urine?
squamous epithelial cells
42
What do squamous epithelial cells indicate?
Sample contamination from genital secretions
| - are clinically insignificant
43
What conditions cause free lipid droplets to be present in urine?
- nephrotic syndrome
- major trauma with fat emboli
- lipid storage disorders
- contamination from catheter lubricants or other creams
44
What are urinary casts and how are they formed?
Formed by tamm-horsfall mucoproteins produced by the renal tubular cells in thick ascending loop of henle and trapped elements
Formed when there is urinary stasis, excess protein, acidic pH or concentrated ultrafiltrate
45
What are hyaline casts comprised of? What is the clinical significance?
Just tamm-horsfall mucoproteins without cells
Non specific finding
- increased in exercise, fever, and dehydration
46
What are granular casts comprised of? What is the clinical significance?
Casts with mucoproteins and cells that have started to degenerate. fine granular --> coarse --> waxy casts
Non-specific finding
47
What are broad casts? What are their clinical significance?
Wide casts formed in the dilated renal tubules
Indicate advanced CKD
48
What is the clinical significance of RBC casts?
suggest glomerular disease or severe tubular damage
49
What is the clinical significance of WBC casts?
associated with pyelonephritis, acute interstitial nephritis, and glomerulonephritis
50
What is the clinical significance of renal tubular epithelial casts?
Found in cases of renal tubular injury
- ATN
- AIN
- transplant rejection
- nephrotoxic exposure
- glomerulonephritis
51
What is the clinical significance of fatty casts?
nephrotic syndrome or lipid storage disorders
52
What are the 3 types of urinary crystals?
1. common crystals: uric acid, calcium oxalate, triple phosphate ...
2. Cholesterol, cystine bilirubin ...
3. Drug crystals
53
What do uric acid crystals look like and what is their clinical significance?
Yellow/orange/brown with multiple shapes
Found in acidic urine
Usually not clinically significant unless at high levels and associated with AKI which may indicate tumour lysis syndrome
54
What do calcium oxalate crystals look like and what is their clinical significance?
colourless dumbbell-or bipyramidal shaped
form in any pH
usually not of clinical significance. If associated with AKI may suggest ethylene glycol poisoning
55
What do calcium phosphate crystals look like and what is their clinical significance?
colourless, wedge-like prisms in rosette or stellar forms
form in basic urine
no significance
56
What do struvite crystals look like and what is their clinical significance?
colourless coffin lid shaped
form in basic urine
may be normal or associated with UTI caused by urea splitting organisms like Klebsiella or proteus
57
What do cysteine crystals look like and what is their clinical significance?
colurless, hexagonal and often heaped under one another
Pathognomonic for cystinuria which is an inherited defect in the reabsorption of cystine and other dibasic AA in the PCT
58
What do cholesterol crystals look like and what is their clinical significance?
Transparent, flat, rectangular plates with notched corners
Seen in nephrotic syndrome and lipid storage disorders
59
What do bilirubin crystals look like and what is their clinical significance?
Small clusters of yellow brown needles
Seen in severe liver disease when serum conjugated bilirubin is elevated
60
What 4 conditions make it more likely for precipitation of drug crystals to occur?
- overdose
- rapid IV bolus
- dehydration
- hypoalbuminemia
61
The glomerular capillary wall is permeable to substances with a molecular weight of ___
<20kDa
62
What are the 4 types of proteinuria?
1. Glomerular
2. Tubular
3. Overflow
4. Post-renal
63
Describe the pathophysiology of glomerular proteinuria
glomerular damage leads to an increased filtration of macromolecules like albumin and other serum proteins leading to abundant urine protein
64
Describe the pathophysiology of tubular proteinuria
interference with tubular reabsorption of normally filtered low molecular weight proteins leads to small amounts of urinary protein (2-3g/day)
65
Describe the pathophysiology of overflow proteinuria
excess low molecular weight proteins in the serum are filtered and exceed the resorptive capacity of the PCT
- ex: Ig light chains in MM, myglobin in rhabdo, or free Hgb in intravascular hemolysis
66
Describe the pathophysiology of post-renal proteinuria
Infection/inflammation/stones/tumours of the LUT lead to small amounts of protein (<1g/day)
67
What is the gold standard for protein assessment?
24 hour urine collection
| - can check for SPE, and albumin and protein excretion rates
68
What does the urine albumin to creatinine ratio tell you?
Can help you...
1. generate a prognosis
2. diagnose and manage diabetic nephropathy
3. stage CKD
69
Why is the ACR a good test? How does it work?
albumin is usually <15-20% of total urine protein and creatinine production is pretty constant throughout the day. An increase in albumin excretion is a more sensitive and specific marker for glomerular basement membrane then total urine protein
70
What conditions can be prognosticated with an increase in the ACR?
- CKD progression
- increase in cardiovascular mortality
- increase in all cause mortality
71
How often should urine ACR be tested in diabetics?
annually
