Urinalysis

Question 1

“clean-catch” urine sample definition

Answer 1

• 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

Question 2

Main methods of urine collection (5)

Answer 2

• 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

Question 3

Major types of urinalysis (5)

Answer 3

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

Question 4

Macroscopic characteristics of normal urine

Answer 4

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

Question 5

Abnormal urine odors

Answer 5

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

Question 6

Abnormal urine colors

Answer 6

• 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)

Question 7

Abnormal turbidity on macroscopic exam

Answer 7

• 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.

Question 8

Chemical urinalysis: Glucose

Answer 8

• 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

Question 9

Chemical urinalysis: Bilirubin

Answer 9

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

Question 10

Chemical urinalysis: ketones

Answer 10

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

Question 11

Chemical urinalysis: specific gravity

Answer 11

• = 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

Question 12

Chemical urinalysis: blood

Answer 12

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

Question 13

Hematuria vs. Hemoglobinuria

Answer 13

• 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

Question 14

Chemical analysis: pH

Answer 14

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

Question 15

Chemical analysis: protein

Answer 15

• 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

Question 16

Chemical analysis: Urobilinogen, Nitrite, Leukocyte Esterase

Answer 16

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

Question 17

Abnormal findings on microscopic examination

Answer 17

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

Question 18

Microscopic examination: RBCs

Answer 18

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

Question 19

Microscopic examination: WBCs

Answer 19

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

Question 20

Microscopic examination: Epithelial cells

Answer 20

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

Question 21

Microscopic examination: casts

Answer 21

• 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

Question 22

Microscopic examination: bacteria, yeast

Answer 22

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

Question 23

Process of cytological examination

Answer 23

• 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