Urine

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Human Urine Sample

Steven C. Campbell, M.D., Ph.D. Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.
Synonyms and keywords: Urinary findings; Urinary abnormalities; Findings on urine exam; Urine; Urine composition; Urine output

Overview

Urine is a fluid produced by humans through the kidney, collected in the bladder, and excreted through the genital urethra. Urine formation helps to maintain the balance of minerals and other substances in the body. Urinary findings may be qualitative or quantitative. Qualitative urinary findings are often analyzed on urinalysis and urine culture. Quantitative urinary findings depends on urine output.

Composition of Urine

Urea structure









The following is a list of normal urine constituents:

Alogithm of Common Urinary Findings

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Urinary Findings
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Quality (Composition)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Quantity (Volume)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Urinalysis
 
 
 
Urine culture
 
 
 
 
 
 
 
 
 
 
 
 
 
Urine output
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
High urine output
 
 
 
 
Low urine output
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Urine odor
 
Urine color and turbidity
 
Specific gravity/osmolality
 
Urinary pH
 
Hematuria
 
Pyuria
 
Proteinuria
 
Cells
 
Casts and Crystals
 
Other
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Polyuria
 
 
Oliguria
 
Anuria
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


Urine Odor

Urine is usually odorless but can produce pungent smells following the consumption of certain foods (e.g. asparagus)

Urine Color and Turbidity

Color

Below is a list of common urine discolorations and their associated diseases.

  • Clear or light yellow
  • Dark yellow
    • Dehydration
  • Greenish yellow color
    • Vitamin B ingestion
  • Orange color
  • Dark red color
    • Hematuria
    • Myoglobinuria
    • Ingestion of certain foods: berries, colored candy, and beets
  • Brown color
    • Hematuria
    • Myoglobinuria
    • Porphyria
    • Hyperbilirubinemia
  • Black (melanuria)
    • Sarcoma
    • Alkaptonuria

Turbidity

  • Normal urine is usually clear
  • Turbid urine may be a manifestation of urinary bacterial infection, hematuria, proteinuria, pyuria, or presence of crystals and casts.

Urine Specific Gravity and Osmolality

Urine Specific Gravity

  • Normal urine specific gravity (density) ranges between 1.003 and 1.035 g.cm-3.
  • Specific gravity outside the normal range may sometimes be associated with urinary disorders.

Urine Osmolality

  • In healthy individuals with restricted fluid intake, urine osmolality should be > than 800mOsm/kg.
  • 24-hour urine osmolality normally ranges between 500 and 800 mOsm/kg.
  • Random urine osmolality normally ranges between 50 and 1400 mOsm/kg.

Increased urine osmolality

Decreased urine osmolality

Urinary pH

  • The pH of urine is normally close to neutral pH=6-7 (Range: 4.5 to 8.2).
  • Strongly acidic or alkaline urine may be manifestations of the following:

Renal and urologic diseases

  • Urinary tract infection
  • Acute kidney injury
  • Chronic kindey disease
  • Renal tubular acidosis

Systemic diseases

Drug administration

Hematuria

  • Microscopic hematuria
  • Gross hematuria

Pyuria

  • Microscopic pyuria
  • Gross pyuria

Proteinuria

  • Albuminuria
    • Microalbuminuria
    • Macroalbuminuria
  • Paraproteinuria

Cells

  • Benign
  • Malignant

Casts and Crystals

Casts

Acellular casts

  • Hyaline casts
  • Granular casts
  • Waxy casts
  • Fatty casts
  • Pigment casts
  • Crystal casts

Cellular casts

  • RBC casts
  • WBC casts
  • Bacterial casts
  • Epithelial cell casts

Crystals

  • Struvite crystals (magnesium-ammonium-phosphate)
  • Bilirubin crystals
  • Calcium carbonate crystals
  • Amorphous crystals
  • Calcium oxalate dihydrate crystals
  • Cystine crystals

Other

Urinary beta-HCG (urinary pregnancy test)

Myoglobinuria

Glucosuria

Ketonuria

Bacterial antigens

Sperm

Urinary drug concentration

Dissolved electrolytes or heavy metals

Calciuria (urinary calcium) differential diagnosis:

Catecholamines

Parameter Upper reference range in the urine per 24 hours
Norepinephrine 23-105 micrograms/24 hours
Dopamine 190-450 micrograms/24 hours
Metanephrine 74-297 micrograms/24 hours
Normetanephrine 105-354 micrograms/24 hours
Vanillic acid 3.3-6.5 mg/24 hours
Vanillyl mandelic acid 17-33 micromol/liter (3.3-6.5 mg/24 hour)

Differential Diagnosis of urinary catecholamines

Urine Culture

Normal urine is sterile. Presence of microorganisms in urine may be associated with urinary infections.

  • Fungi
  • Bacteria

Urine Quantity (Volume)

  • The amount of urine produced depends on hydration (volume of fluid intake), physical activity, environmental factors, body surface area, and general health condition.
  • In adult humans, the average urine production is approximately 1 L to 2 L per 24 hours.

High Output

  • Polyuria: Excessive urinary production > 2.5 L per 24 hours

Low Output

  • Oliguria: Urine production < 400 mL / 24 hours in adults. A more specific definition includes the following:
    • Infants: oliguria is defined as urine output < 1 mL/kg/hr[1]
    • Children: Oliguria is defined as urine output < 0.5 mL/kg/hr.
    • Aduults: Oliguria is defined as urine output < 17 to 21 ml/hr.

For a detailed explanation of oliguria, click here.

  • Anuria: Urine production < 100 mL / 24 hr

For a detailed explanation of anuria, click here.

References

  1. Klahr S, Miller S (1998). "Acute oliguria". N Engl J Med. 338 (10): 671–5. doi:10.1056/NEJM199803053381007. PMID 9486997. Free Full Text.


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