URINALYSIS

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URINALYSIS
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• The urinalysis is a fundamental test that should
  be performed in all urologic patients
• A complete urinalysis includes both chemical and
  microscopic analyses.

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Reasons for inadequate urinalyses include

• Improper collection,
• Failure to examine the specimen immediately,
• Incomplete examination (eg, most laboratories do
  not perform a microscopic analysis unless it is
  specifically requested by the provider),
• Inexperience of the examiner, and
• (5) Inadequate appreciation of the significance
  of the findings.

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Collection of Urinary Specimens

• In the male patient, a midstream urine sample is
  obtained
• The four aliquots have been designated Voided
  Bladder 1, Voided Bladder 2, Expressed Prostatic
  Secretions, and Voided Bladder 3 (VB1, VB2, EPS,
  and VB3)
• To evaluate for a possible infection in a female,
  a catheterized urine sample should always be
  obtained.
• All urine samples should be examined within 1
  hour of collection and plated for culture and
  sensitivity if indicated for Neonates and Infants

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Physical Examination of Urine

• The physical examination of the urine includes an
  evaluation of color, turbidity, specific gravity
  and osmolality, and pH.

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Color

• The normal pale yellow color of urine is due to
  the presence of the pigment urochrome
• Urine color varies most commonly because of
  concentration, but many foods, medications,
  metabolic products, and infection may produce
  abnormal urine color.

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Common Causes of Abnormal Urine Color
Colorless Very dilute urine
Colorless Overhydration
Cloudy/milky Phosphaturia
Cloudy/milky Pyuria
Cloudy/milky Chyluria
Red Hematuria
Red Hemoglobinuria/myoglobinuria
Red Anthrocyanin in beets and blackberries
Red Chronic lead and mercury poisoning
Red Phenolphthalein (in bowel evacuants)
Red Phenothiazines (e.g., Compazine)
Red Rifampin
Orange Dehydration
Orange Phenazopyridine (Pyridium)
Orange Sulfasalazine (Azulfidine)
Yellow Normal
Yellow Phenacetin
Yellow Riboflavin
Green-blue Biliverdin
Green-blue Indicanuria (tryptophan indole metabolites)
Green-blue Amitriptyline (Elavil)
Green-blue Indigo carmine
Green-blue Methylene blue
Green-blue Phenois (e.g., IV cimetidine Tagamet,
Green-blue IV promethazine Phenergan)
Green-blue Resorcinol
Green-blue Triamterene (Dyrenium)
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Brown Urobilinogen
Brown Porphyria
Brown Aloe, fava beans, and rhubarb
Brown Chloroquine and primaquine
Brown Furazolidone (Furoxone)
Brown Metronidazole (Flagyl)
Brown Nitrofurantoin (Furadantin)
Brown-black Alcaptonuria (homogentisic acid)
Brown-black Hemorrhage
Brown-black Melanin
Brown-black Tyrosinosis (hydroxyphenylpyruvic acid)
Brown-black Cascara, senna (laxatives)
Brown-black Methocarbamol (Robaxin)
Brown-black Methyldopa (Aldomet)
Brown-black Sorbitol
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Turbidity

• Cloudy urine is most commonly due to phosphaturia
• The large numbers of white blood cells cause the
  urine to become turbid.
• Pyuria is readily distinguished from
  phosphaturia either by smelling the urine
  (infected urine has a characteristic pungent
  odor)
• Rare causes of cloudy urine include chyluria (in
  which there is an abnormal communication between
  the lymphatic system and the urinary tract
  resulting in lymph fluid being mixed with urine),
  lipiduria, hyperoxaluria, and hyperuricosuria.

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Specific Gravity and Osmolality

• Specific gravity of urine is easily determined
  from a urinary dipstick and usually varies from
  1.001 to 1.035.
• A specific gravity less than 1.008 is regarded as
  dilute, and a specific gravity greater than 1.020
  is considered concentrated
• Conditions that decrease specific gravity include
  --
• increased fluid intake,
• (2) diuretics,
• (3) decreased renal concentrating ability, and
• (4) diabetes insipidus.
• Conditions that increase specific gravity
  include--
• (1) decreased fluid intake
• (2) dehydration owing to fever, sweating,
  vomiting, and diarrhea
• (3) diabetes mellitus (glucosuria) and
• (4) inappropriate secretion of antidiuretic
  hormone.
• Osmolality is a measure of the amount of material
  dissolved in the urine and usually varies between
  50 and 1200 mOsm/L.

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pH

• Urinary pH is measured with a dipstick test
  strip( methyl red and bromothymol blue), which
  yield clearly distinguishable colors over the pH
  range from 5 to 9.
• Urinary pH may vary from 4.5 to 8
• The average pH varies between 5.5 and 6.5.
• A urinary pH between 4.5 and 5.5 is considered
  acidic, whereas a pH between 6.5 and 8 is
  considered alkaline.

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• In patients with a presumed UTI, an alkaline
  urine with a pH greater than 7.5 suggests
  infection with a urea-splitting organism, most
  commonly Proteus.
• Urinary pH is usually acidic in patients with
  uric acid and cystine lithiasis.
• Alkalinization of the urine is an important
  feature of therapy in both of these conditions

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Chemical Examination of Urine

• Urine dipsticks provide a quick and inexpensive
  method for detecting abnormal substances within
  the urine
• The abnormal substances commonly tested for with
  a dipstick include
• blood,
• (2) protein,
• (3) glucose,
• (4) ketones,
• (5) urobilinogen and bilirubin, and
• (6) white blood cells.

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Hematuria

• Normal urine should contain less than three red
  blood cells per HPF.
• A positive dipstick for blood in the urine
  indicates either hematuria, hemoglobinuria, or
  myoglobinuria.
• The chemical detection of blood in the urine is
  based on the peroxidase-like activity of
  hemoglobin
• Hematuria can be distinguished from
  hemoglobinuria and myoglobinuria by microscopic
  examination of the centrifuged urine
• The presence of a large number of erythrocytes
  establishes the diagnosis of hematuria.
• If erythrocytes are absent, examination of the
  serum will distinguish hemoglobinuria and
  myoglobinuria

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Differential Diagnosis and Evaluation of
Hematuria.

• Hematuria may reflect either significant
  nephrologic or urologic disease
• Hematuria of nephrologic origin is frequently
  associated with casts in the urine and almost
  always associated with significant proteinuria.
• Even significant hematuria of urologic origin
  will not elevate the protein concentration in the
  urine into the 100 to 300 mg/dL or 2 to 3 range
  on dipstick.

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Evaluation of glomerular hematuria (dysmorphic
erythrocytes, erythrocyte casts, and
proteinuria). ANA, antinuclear antibody ASO,
antistreptolysin O Ig, immunoglobulin.
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Evaluation of nonglomerular renal hematuria
(circular erythrocytes, no erythrocyte casts, and
proteinuria). CT, computed tomography IgA,
immunoglobulin A IVU, intravenous urography PT,
prothrombin time PTT, partial thromboplastin
time
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Evaluation of essential hematuria (circular
erythrocytes, no erythrocyte casts, no
significant proteinuria). CT, computed
tomography IVU, intravenous urography
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Proteinuria

• Healthy adults excrete 80 to 150 mg of protein in
  the urine daily
• Proteinuria may be the first indication of
  renovascular, glomerular, or tubulointerstitial
  renal disease, or it may represent the overflow
  of abnormal proteins into the urine in conditions
  such as multiple myeloma.
• Normally, urine protein is about 30 albumin, 30
  serum globulins, and 40 tissue proteins, of
  which the major component is Tamm-Horsfall
  protein.

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Evaluation of proteinuria.
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Glucose and Ketones

• Urine testing for glucose and ketones is useful
  in screening patients for diabetes mellitus
• A serum glucose of about 180 mg/dL above this
  level, glucose will be detected in the urine.
• Ketones are not normally found in the urine but
  will appear when the carbohydrate supplies in the
  body are depleted and body fat breakdown occurs
• Ketones excreted include acetoacetic acid,
  acetone, and ß-hydroxybutyric acid. With abnormal
  fat breakdown, ketones will appear in the urine
  before the serum.

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Bilirubin and Urobilinogen

• Normal urine contains no bilirubin and only very
  small amounts of urobilinogen
• Conjugated bilirubin has a low molecular weight,
  is water soluble, and normally passes from the
  liver into the small intestine through the bile
  ducts, where it is converted to urobilinogen.
• Therefore, conjugated bilirubin does not appear
  in the urine except in pathologic conditions in
  which there is intrinsic hepatic disease or
  obstruction of the bile ducts.
• Indirect bilirubin is of high molecular weight
  and bound in the serum to albumin. It is water
  insoluble and, therefore, does not appear in the
  urine even in pathologic conditions.
• Urobilinogen is the end product of conjugated
  bilirubin metabolism.

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Leukocyte Esterase and Nitrite Tests

• Leukocyte esterase activity indicates the
  presence of white blood cells in the urine.
• The presence of nitrites in the urine is strongly
  suggestive of bacteriuria
• The major cause of false-positive leukocyte
  esterase tests is specimen contamination
• Nitrites are not normally found in the urine, but
  many species of gram-negative bacteria can
  convert nitrates to nitrites

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Protocol for determining the need for urine
sediment microscopy in an asymptomatic population
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Microscopy Technique

• Low-power magnification is sufficient to identify
  erythrocytes, leukocytes, casts, cystine
  crystals, oval fat macrophages, and parasites
  such as Trichomonas vaginalis and Schistosoma
  hematobium.
• High-power magnification is necessary to
  distinguish circular from dysmorphic
  erythrocytes, to identify other types of
  crystals, and, particularly, to identify bacteria
  and yeast
• The urinary sediment should be examined
  microscopically for (1) cells, (2) casts, (3)
  crystals, (4) bacteria, (5) yeast, and (6)
  parasites

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Cells
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Casts

• Tamm-Horsfall mucoprotein is the basic matrix of
  all renal casts it originates from tubular
  epithelial cells and is always present in the
  urine
• When the casts contain only mucoproteins, they
  are called hyaline casts and may not have any
  pathologic significance.
• Red blood cell casts contain entrapped
  erythrocytes and are diagnostic of glomerular
  bleeding, most likely secondary to
  glomerulonephritis
• White blood cell casts are observed in acute
  glomerulonephritis, acute pyelonephritis, and
  acute tubulointerstitial nephritis
• Granular and waxy casts result from further
  degeneration of cellular elements.
• Fatty casts are seen in nephrotic syndrome,
  lipiduria, and hypothyroidism.

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Crystals

• Identification of crystals in the urine is
  particularly important in patients with stone
  disease
• The identification of cystine crystals
  establishes the diagnosis of cystinuria
• Crystals precipitated in acidic urine include
  calcium oxalate, uric acid, and cystine.
• Crystals precipitated in an alkaline urine
  include calcium phosphate and triple-phosphate
  (struvite) crystals.

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Urinary crystals
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Bacteria

• Normal urine should not contain bacteria.
• In a fresh uncontaminated specimen, the finding
  of bacteria is indicative of a UTI.
• Because each HPF views between 1/20,000 and
  1/50,000 mL, each bacterium seen per HPF
  signifies a bacterial count of more than
  20,000/mL.
• Therefore, 5 bacteria/HPF reflects colony counts
  of about 100,000/mL.

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Yeast

• The most common yeast cells found in urine are
  Candida albicans
• Yeasts are most commonly seen in the urine of
  patients with diabetes mellitus or as
  contaminants in women with vaginal candidiasis.

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Parasites

• Trichomonas vaginalis is a frequent cause of
  vaginitis in women and occasionally of urethritis
  in men