1. Lab Medicine Conference :
Urinalysis
Jim Holliman, M.D., F.A.C.E.P.
Professor of Surgery and Emergency Medicine
Director, Center for International Emergency Medicine
M. S. Hershey Medical Center
Penn State University
Hershey, Pennsylvania, U.S.A.

2. Indications for Urinalysis
Suspect / confirm UTI
R/O primary renal disease
R/O systemic disease with major renal manifestation
Assess complications of hypertension
Assess presence or amount of endogenous or exogenous excreted substances

3. Complete Urinalysis : Components
Color / appearance
Specific gravity pH
Chemistries
protein
glucose
ketones
bilirubin / urobilinogen
hemoglobin / blood
nitrite
leucocyte esterase
Microscopic exam
cells / casts
bacteria
other organisms
crystals

4. Secondary, Optional Tests on Urine
Culture
Quantitative culture
Sensitivity
Gram stain
Acid-fast stain
Protein electrophoresis
Antigen detection (immunofluorescence)
Quantitative assays

5. What is Urine, Anyway ? 95 % water, 5 % solids 3 main components :
urea
NaCl
Color from pigments urochrome & urobilin
Intensity of color parallels degree of contamination

6. Urinalysis : Important Aspects of Collection
"Clean - voided" specimen necessary if micro exam to be done
Cleansing of urethral meatus
Preinsert tampon if discharge present
Hold labia minora apart
Midstream specimen
"Mini-cath" is option to reliably avoid menstrual or vaginal discharge contamination
Adhesive perineal bag vs. direct bladder puncture with 22 g. needle are collection options for peds patients (or try "Perez reflex")

7. “Minicath” urine collection tube

8. Problems with Delayed Analysis of Unrefrigerated Urine
Bacteria split urea to ammonia, & urine becomes alkaline
Casts decompose
Red cells lyse
Bacterial counts increase
Glucose decreases

9. Diagnostic Clues from Urine Odor
Volatile acids responsible for normal urine odor
Specific odors & dx's :
Acetone : DKA
Ammonia : infection with urea breakdown
Maple Syrup Urine Disease
Asparagus or garlic ingestion

10. Causes of Increased Turbidity of Urine
Urate crystals in acid urine
Phosphates in alkaline urine
RBC's
WBC's
Bacteria
Vaginal secretions
Fat globules

11. Differential diagnosis of red-orange urine color

12. Differential diagnosis of red or pink urine color

13. Differential diagnosis of purple urine color

14. Differential diagnosis of red-brown urine color

15. Differential diagnosis of brown-black urine color

16. Differential diagnosis of yellow-brown urine color

17. Differential diagnosis of yellow urine color

18. Differential diagnosis of yellow-orange urine color

19. Differential diagnosis of colorless urine

20. Differential diagnosis of milky-colored urine

21. Parasitic chyluria due to Wucheria bancrofti or other filaria ; can cause thoracic duct fistulas to the kidney or bladder

22. Differential diagnosis of blue-green urine color

23. Differential diagnosis of brown-green urine color

24. Differential diagnosis of yellow-green urine color

25. Interpretation of Specific Gravity in U/A's
S.G. is the ratio of urine density compared to a water standard
S.G. indirectly measures renal concentrating ability
Is measured by dipstick or refractometer
S.G. values :
Distilled water : 1.000
Dilute urine : to 1.010
Concentrated urine : to 1.030
Correlation with osmolarity :
S.G = osmolarity 285 (same as serum)
S.G = osmolarity > 600

26. Causes of Falsely High S.G. Readings
Excretion of radiopaque contrast media
Excessive proteinuria (as in nephrosis or diabetes)
Excessive glycosuria
Refrigerated urine

27. Diagnostic Clues from Urine pH
Range 4.6 to 8 ; normal about 6
Animal protein diet : acid urine
Vegetable / fruit diet : alkaline urine
Stones that develop in alkaline urine :
Calcium phosphate
Calcium carbonate
Mg PO4
Stones that develop in acid urine :
Uric acid
Cysteine
Calcium oxalate

28. Protein Analysis in U/A's
Normal urine contains small amounts of albumin & globulin
Proteinuria exists if > 20 mg/dl
Incidence 6 to 9 % in asymptomatic patients
Dipstick tests use tetrabromophenol blue indicator system (yellow to green as conc. increases)
React mainly with albumin
False positive with quaternary ammonia compounds & phenazopyridine dyes

29. Clinitest Use for Detection of Glycosuria
Based on reduction of metal ions by glucose
False positive reactions due to :
Hypochlorite or chlorine
Other sugars (galactose, lactose, fructose, maltose, as during pregnancy)
Enzyme - based tests (glucose oxidase) are more specific for glucose
Can have false negative results with ascorbic acid, tetracycline, or high uric acid

30. Correlation of Urine Glucose Readings
mg/deciliter Glucose
Negative
Trace
100 1+
250 2+
1000 3+
2000 4+
>2000

31. Analysis for Ketones in U/A's
Choices are :
Acetest (tablet)
Test tube (Rothera)
Dipstick
All use reaction between acetoacetic acid & nitroprusside to make a violet dye complex
Acetone reaction is < 5 % of color change
Beta-hydroxybutyrate not detected

32. Causes of False Positive Urine Ketones
Levodopa
Phenolphthalein (in laxatives)
Insulin
Pyridium (phenazopyridine)
Phenformin
Phenylketonuria

33. Analysis of Bilirubin in U/A's
Conjugated bilirubin in normal urine up to mg/dl
Dipstick uses diazonium salt reagent (buff to pink to brown)
Positive test for urinary bilirubin with a negative urine urobilinogen indicates biliary obstruction
Phenazopyridine causes false positive
False negatives :
Chlorpromazine, selenium
Exposure to light (inactivates to biliverdin)

34. Analysis of Urobilinogen in U/A's
Is colorless
Produced as byproduct of bacterial degradation of conjugated bilirubin ; enterohepatic circulation accounts for normal urinary excretion
Is increased with hemolysis or liver disease, & decreased with biliary obstruction
Phenazopyridine causes false positive
High nitrates cause false negative (as in red wines)

35. Analysis of Hemoglobin in U/A's
Not detectable by naked eye unless > 1:1000 blood in urine
Uses peroxidase characteristic of hemoglobin or myoglobin to change color of chromogen
Dipsticks detect both free Hgb & myoglobin, and intact RBC's
False positives from bromides, copper, iodides, oxidizing agents
False negative from ascorbic acid

36. Analysis of Nitrites in U/A's
Nitrites absent from normal urine
Most UTI bacteria reduce urinary nitrates to nitrites using enzyme nitrate reductase
Dipstick uses aromatic amine & diazonium compound to produce pink color in presence of nitrite
False positive rare ( can be due to phenazopyridine)
False negatives :
Bacterial inhibition with antibiotics
High urine flow (dilutional) ; Frequent or continuous (foley) voiding
Ascorbic acid

37. Analysis of Leucocyte Esterase in U/A's
Any purple color on dipstick indicates > 5 WBC's/hpf
Detects intact & lysed WBC's & WBC casts
False negatives :
Cephalexin, gentamicin, nitrofurantoin
Up to 97 % sensitivity & 90 % specificity for culture - proven UTI's

38. Use of "Reflex Urinalysis" at Hershey Medical Center
"Reflex U/A" = dipstick (Chem 9)
Micro exam done at no extra charge if dip is positive for protein, Hgb, or leucocyte esterase
Is indicated for routine U/A's as part of routine physical exam, and in other patients without possible urologic sx

39. Costs for U/A's at Hershey Medical Center
$17.00 for inpatients
$12.00 for outpatients
If microscopic U/A ordered separately :
Add $15.00 for inpatients
Add $13.00 for outpatients
Urine culture is $32.00
Urine C&S is $79.00

40. Rationale for Use of Dipstick as Screening for Micro Exam of Urine
5 combined studies : 3205 patients
Sensitivity : 94 %
Specificity : 72 %
HMC study : 50 patients
Sensitivity : 93 %
Post - test probability of abnormal urine sediment if reflex U/A is negative is 1 to 6 %

41. Analysis of WBC's in Urine
Normal WBC excretion in urine :
Up to 400,000 cells per hour
Averages 650,000 per day
10 WBC per ml. correlates with 1 WBC per hpf
Counts exceeding 10 WBC per ml. correlate with significant bactiuria in 40 to 84 %
Can have false negative if patient is leucopenic

42. White blood cells in urine

43. Causes of Sterile Pyuria
Balanitis or urethritis
Bladder tumors
Calculi
Exercise
Fever
Glomerulonephritis
Renal tuberculosis
Viral infections

44. Analysis of RBC's in Urine
Normal RBC excretion in urine :
Up to 1,000,000 per day
Average 130,000 per day
So average is 1 RBC per 2 to 3 hpf or 500 to 1000 RBC per ml.
Hematuria then represents greater amounts of blood than these
For urine to be considered free of blood, both supernatant & sediment should be dipstick tested

45. Red blood cells in urine

46. Gross hematuria from congenital urethral stricture

47. Analysis for Bacteria in U/A's
Bacteria are absent in normal bladder urine
Micturition commonly deposits bacteria in urine
Classic infection definition : > 100,000 organisms per ml. of freshly centrifuged, freshly voided urine
Correlations with infection :
Detection of any bacteria on uncentrifuged specimen
> 10 bacteria / hpf of centrifuged sample

48. Bacterial urethritis
(should be treated with topical and oral anti-Staph antibiotics)

49. Bacterial Counts in Urine
< 1000 colonies per ml. implies only contamination
Counts > 1000 and < 100,000 per ml. may imply infection
Counts > 100,000 / ml. almost always imply infection
Causes of false low counts :
pH < 5, S.G. < 1.003, voiding < 45 minutes from sample collection, urethral obstruction, infections with fastidious organisms, contaminants with string oxidants (bleach)

50. Diagnostic Significance of Cellular Casts
Represents contents of renal tubules discharged into urine
Cast width descriptions :
Narrow : 1 to 2 RBC's in width
Medium : 3 to 4 RBC's in width
Broad : > 5 RBC's in width ; these are formed in the collecting tubules & suggest severe renal disease
Cast types & associated diseases :
Broad, epithelial, fatty, granular, or waxy : parenchymal renal disease
RBC : acute glomerulonephritis
WBC : pyelonephritis

51. Diagnostic Aspects of Cellular Casts
RBC casts
Usually represent significant glomerular disease
Can occur after very strenuous exercise
Alkaline urine hemolyzes RBC's & can dissolve casts if analysis delayed
Hyaline casts
Clear, colorless ; due to protein precipitation
Occurence depends on urine flow, pH, degree of proteinuria
Granular casts
Result from disintegration of cell material into particles
Form waxy casts when renal failure is advanced

54. Hyaline casts from protein gel in the renal tubule ; normal sediment has one to two per high power field

55. Granular casts

56. Red blood cell casts

57. White blood cell cast

58. Red cell casts in acute glomerulonephritis

59. Waxy granular and cellular casts in chronic glomerulonephritis

60. Hyaline cast with epithelial cells in tubulo-interstitial disease

61. Analysis for Crystals in U/A's
Crystals commonly found in normal urine
Pathologic crystals :
Cysteine (hexagonal ; not birefingent under polarized light, unlike uric acid)
Leucine (yellow spheres with striations)
Tyrosine (fine needles in rosettes)
Phosphate & urate crystals of little Dx significance
Calcium oxalate crystals sometimes indicate ethylene glycol poisoning (but can be normal)

62. Crystals found chiefly in alkaline urine

63. Crystals found chiefly in acid urine
Sulfonamide crystals
Crystals found chiefly in acid urine

64. Ammonio-magnesium-phosphate (struvite) crystal due to chronic U. T. I
Ammonio-magnesium-phosphate (struvite) crystal due to chronic U.T.I. with Proteus (alkaline urine)

65. Uric acid crystals under bright field microscopy

66. Uric acid crystals under polarized light

67. Tyrosine crystals under bright field microscopy

68. Leucine crystals under bright field microscopy

69. Cystine crystals under bright field microscopy

70. Uric acid crystals in a 3 month old patient evaluated for orange diaper stains ; this situation calls for evaluation of renal function tests

71. Miscellaneous Agents Detectable on U/A Micro Exam
Spermatozoa
Trichomonads
Candida albicans
Rarely Giardia or Entamoeba histolytica
Other parasites
Schistosoma
Nematodes

72. Trichomonas vaginalis in urine

73. Candida albicans in urine

74. Measurements of Electrolytes in Urine
Ion specific electrodes currently used (same as for serum)
Clinical situations where measurements useful :
Sodium
Volume depletion, acute oliguria, hyponatremia (R/O SIADH)
Chloride
Determine if metabolic alkalosis is chloride resistant or sensitive
Potassium
Determine site of K+ loss in hypokalemia (if < 10 meq/liter, implies GI tract as source)

75. Interpretation of Urinary Chloride Levels in Metabolic Alkalosis
Urinary chloride 0 to 10 meq/liter ("chloride-responsive") :
Vomiting
NG suction
Diuretic effect
Post-hypercapnia
Urinary chloride > 10 meq/liter (approx. dietary intake) :
Severe hypokalemia
Renal failure
Edematous states
Mineralocorticoid excess
Licorice ingestion

76. Suggested Criteria for Obtaining Urine Cultures if UTI Suspected
All children (age < 14)
All males
Women with history of :
Immunocompromise
Renal abnormalities
Diabetes mellitus
Recent instrumentation
Indwelling catheter
Prolonged Sx before seeking care
3 or more ( ? > 5 ) UTI's in last year
Recent pyelonephritis
Recent hospitalization

77. Lab Medicine Conference : Urinalysis Summary
Assess urine color & overall appearance
Decide if only dipstick analysis needed
Consider explanations for each abnormal component on dipstick & micro
Decide if additional studies (C & S, electrolytes, osmolality, etc.) needed