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CVPR: Renal > Urinalysis > Flashcards

Flashcards in Urinalysis Deck (23)
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1

"clean-catch" urine sample definition

  • sample of urine collected midstream
  1. clean urethral area
  2. after some urine falls into toilet bowl, clear container is used to catch 1-2 oz

2

Main methods of urine collection (5)

  • random collection = no precautions to contamination
  • early morning collection = sample before ingesting fluid (usually hypertonic)
  • clean-catch = midstream urine specimen
  • catheterization = usually comatose/confused pts
  • suprapubic needle aspiration = purest sample; often in infants/small children 

3

Major types of urinalysis (5)

  • macroscopic exam
  • chemical analysis (urine dipstick)
  • microscopic exam
  • culture
  • cytological examination

4

Macroscopic characteristics of normal urine

  • color = pale ==> dark yellow/amber
  • clear (i.e. not cloudy)
  • normal volume = 750 - 2000 ml/24hr

5

Abnormal urine odors

- Ammonia-like: (Urea-splitting bacteria)
- Foul, offensive: Old specimen, pus or inflammation
- Sweet: Glucose
- Fruity: Ketones
- Maple syrup-like: (Maple Syrup Urine Disease)

6

Abnormal urine colors

- Colorless: Diluted urine
- Deep Yellow: Concentrated Urine, Riboflavin
- Yellow-Green: Bilirubin / Biliverdin
- Red: Blood / Hemoglobin
- Brownish-red: Acidified Blood (Acute GN)
- Brownish-black: Homogentisic acid (Melanin)

 

7

Abnormal turbidity on macroscopic exam

- Typically cells or crystals.
- Cellular elements and bacteria will clear by centrifugation.
- Crystals dissolved by a variety of methods.
- Microscopic examination will determine which is present.

8

Chemical urinalysis: Glucose

  • normal glucose <0.1% of that filtered by glomerulus = < 130mg/24hr
  • glycosuria = (usually) diabetes mellitus
  • strip = glucose oxidase + peroxide + potassium iodide + blue dye
    • O2 produced by enzymes reacts w/blue to change color
    • compare w/chart to see ~amount
  • false-negatives in pregnant women

9

Chemical urinalysis: Bilirubin

  • bilirubin + diazotized dicholoraniline ==> tan colors
  • false +: indican
  • false -: ascorbate

10

Chemical urinalysis: ketones

  • diabetic ketosis or calorie deprivation ==> ketones
  • ketone + nitroprusside ==> color change
    • pink (negative) ==> purple (positive)

11

Chemical urinalysis: specific gravity

  • = weight of urine/weight of same volume of pure water
  • test measures tubular fxn 
  • SG ~ density of urine ==> measures ability of kidney to concentrate/dilute
  • ~SG via measuring pKa change in relation to ionic concentration of urine

12

Chemical urinalysis: blood

  • pseudoperoxidase rxn = more senstivie to hemoglobin and myoglobin vs. RBCs
  • positive test = myoglobinuria, hemoglobinuria, or hematuria(=most common)

13

Hematuria vs. Hemoglobinuria

  • both ==> positive occult blood test on strip

  • hematuria ==> red, cloudy urine that clears when centrifuged
    • microscope: RBCs


  • hemoglobinuria ==> reddish-brown urine that doesn't clear after centrifugation
    • microscope: no RBCs

14

Chemical analysis: pH

  • Urine normal pH ~ 6 (range 4.5 - 8.0)
  • acidic urine = metabolic acidosis, high protein diet
  • alkaline urine = renal tubular acidosis

15

Chemical analysis: protein

  • most strips detect albumin using indicator dye Bromphenol blue
  • 1+ = ~200-500mg/24hr
  • 2+ = ~.5-1.5g/24hr
  • 3+ = ~2-5g/24hr
  • 4+ = 7g/24hr

16

Chemical analysis: Urobilinogen, Nitrite, Leukocyte Esterase

  • urobilinogen: high in hemolytic crisis or hepatic/intestinal dysfxn
  • nitrite: significant bacteria present in urine
  • leukocyte esterase: postive in presence of WBCs

17

Abnormal findings on microscopic examination

  • RBCs
  • WBCs
  • Epithelial cells
  • Casts (more than normal)
  • Bacteria
  • Yeasts
  • Crystals

18

Microscopic examination: RBCs

  • "hematuria" = anormal #s of RBCs
  • caused by anything that physically damages kidney
  • dysmorphic RBCs ==> glomerulonephritis

19

Microscopic examination: WBCs

  • "pyuria" = abnormal # of leukocytes
  • causes: UTI, acute glomerulonephritis
  • leukocytes usually = granulocytes

20

Microscopic examination: Epithelial cells

  • tubular degeneration ==> increased squamous epithelial cells in urine
  • w/lipiduria ==> cells contain fats

21

Microscopic examination: casts

  • casts formed @ distal tubule or collecting duct
  • hyaline casts = mucoprotein (Tamm-Horsfall) secreted by tubule cells 
    • can be seen in healthy pts
  • protein casts
  • RBC casts ==> glomerulonephritis
  • WBC casts ==> acute pyelonephritis; inflammation of the kidney
  • granular or waxy casts = derived from renal tubular cells

22

Microscopic examination: bacteria, yeast

  • bacteria are common
  • dx of bacteriuria in suspected UTI requires culture
  • yeast = contaminants or true yeast infection

23

Process of cytological examination

  • fresh voided urine after 3-4 hrs
  • look for malignancy using exmaination + staining:
    • papnicolaou
    • wright's
    • immunoperozidase
    • immunofluorescnece
  • dysplasia recognized by nuclear clustering + lack of cytoplasmic clearing