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Flashcards in Chemistry Deck (415)
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1

How can biliuria be assessed macroscopically?

The foam of shaken urine is yellow only when bilirubin is present (not with urobilinogen).

2

What conditions can cause red urine?

Hematuria, hemoglobinuria, myoglobinuria (all dipstick positive)

Drugs (rifampin, pyridium, L-dopa), beets.

3

In what clinical settings can glucose be found in urine?

Blood glucose > 180mg/dL
Pregnancy
Tubular dysfunction

4

How is glucose in urine detected?

Dipstick method (glucose oxidase/peroxidase generates gluconate) - Specific to glucose, affected by ascorbate

Copper sulfate method (Benedict reaction) - Detects all reducing substances (sugars).

5

What is the amount and nature of normal urine protein?

About 150mg per day, mostly Tamm-Horsfall protein. Can increase during dehydration, exercise, and postural proteinuria.

6

How is urine protein detected?

Dipstick method (only detects albumin) - False positives with alkaline urine

Precipitation methods

7

What is the predominant ketone in blood and urine?

b-hydroxybutyrate (80%)
Acetoacetic acid, acetone (20%)

(in settings of DKA; normally closer to 1:1)

8

How are urine ketones detected?

Dipstick test (sensitive to acetoacetic acid, which diminishes over time) - False positives with captopril, methyldopa.

9

How can hematuria, hemoglobinuria, and myoglobinuria be distinguished?

Hematuria - Microscopy demonstrating intact RBCs
Hemoglobinuria - Low haptoglobin, urine siderophages
Myoglobinuria - Elevated CK, history of skelM injury

10

Compare and contrast urinary bilirubin and urinary urobilinogen.

Urinary bilirubin - Abnormal, indicates conjugated hyperbilirubinemia.
Urobilinogen - Normal breakdown product via GI flora. Also increased in conjugated hyperbilirubinemia.

11

Urine nitrite

Screening marker for urease positive uropathogens (E. Coli)

Nitrite negative organisms: Enterococci, neisseria, TB.

12

Urine leukocyte esterase

Screening marker for bacterial cystitis (originates from neutrophils). Can also arise from trichomonads and eosinophils.

13

What conditions are associated with increased or decreased urine specific gravity?

Increased: Dehydration, SIADH, Addison, DM, proteinuria

Decreased: Diabetes insipidus, diuretic therapy, renal failure (isothenuria)

14

What conditions can cause urine alkalinity?

Vegetarian diet
Alkalotic conditions
Urease+ UTI
Renal tubular acidosis
Standing urine sample (becomes more alkaline over time)

15

Nephrolithiasis - Calcium oxalate crystals

Most common stone
Envelope-shaped
Associated with Crohn's and consumption of oxalates (rhubarb, spinach, nuts, antifreeze).

16

Nephrolithiasis - Calcium phosphate stones

Promoted by hypercalciuria, urinary alkalosis, and low urine volume

17

Nephrolithiasis - Struvite stones

Coffin-shaped crystals
Staghorn stones
Promoted by urease+ UTI

18

Nephrolithiasis - Urate stones

Pleomorphic crystals (diamond, square, or rod-like)
Promoted by acidic pH, hyperuricosuria

19

Nephrolithiasis - Cystine stones

Hexagonal crystals
Seen in setting of cystinuria (AutRec disorder of dibasic amino acid transport).

20

Nephrolithiasis - Tyrosine

Needle-like, "Sheaves of wheat" crystals

21

What are the microscopic features of glomerular hematuria?

Dysmorphic RBCs (polymorphic) with casts and erythrophagocytosis

22

What types of casts can be seen in urine, and what do they indicate?

Hyaline - Nonspecific
Granular, Waxy - Renal disease, dehydration
Red cell - Glomerulonephritis
White cell - Tubulointerstitial nephritis
Fatty - Nephrotic syndrome

23

What is normal CSF glucose and protein content?

Glucose - ~60% that of serum
Protein - None

24

Distinguish true subarachnoid bleeds from traumatic taps on CSF analysis.

True xanthochromia (uniform xanthrochromia across all sample tubes) suggests a real bleed. Presence of erythrophagocytosis / siderophages is also helpful.

25

What CSF findings are suggestive of multiple sclerosis?

Elevated CSF IgG (relative to serum) indicates intrathecal IgG synthesis.

Oligoclonal bands (distinctive IgG gamma region bands) in CSF (as compared to serum).

26

What is the pattern of CSF found in bacterial meningitis?

Decreased glucose
Elevated leukocytes (mostly neutrophils)
Elevated protein

27

What is the pattern of CSF found in viral meningitis?

Normal glucose (exception: HSV)
Elevated leukocytes (mostly lymphocytes)
Slightly elevated protein

28

What is the pattern of CSF found in fungal and mycobacterial meningitis?

Decreased glucose
Elevated leukocytes (mostly lymphocytes)
Slightly elevated protein

29

What are light's criteria?

For an effusion to be considered exudative:
Pleural fluid : serum protein > 0.5, OR
Pleural fluid : serum LDH > 0.6, OR
Pleural fluid > 2/3 upper limit of serum LDH

30

Distinguish between chylous and pseudochylous effusion.

Chylous - Caused by lymphatic duct obstruction. Chylomicrons are present and triglycerides are increased.
Pseudochylous - Gradual accumulation of lipids from many conditions; generally fewer triglycerides and no chylomicrons.