Urine

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. A urinalysis (U) is an array of tests performed on urine and is one of the most common methods of medical diagnosis. A part of a urinalysis can be performed by using urine dipsticks, in which the test results can be read as color changes.

Composition of Urine

Urea structure

The following is a list of normal urine constituents:

• Non-organic substances: bicarbonate, chloride, phosphorus, sulphur, bromide, fluoride, iodide, rhodanide, potassium, natron, calcium, magnesium, iron, copper, zinc, cobalt, selenium, arsenium, lead, and mercury.
• Nitrogenous substances: nitrogen, urea, creatine, creatinine, guanidine, choline, carnitine, piperidine, spermidine, dopamine, epinephrine, norepinephrine, serotonin, tryptamine, levulinique amino-acid, and bilirubin
• Non-nitrogenous organic acids
• Amino acids: alanine, carnosine, glycine, histidine, leucine, lysine, methionine, phenylalanine, serine, tyrosine, valine, hydroxyloproline, galactosylhydroxylyzine, xylosylserine, and others.
• Proteins: albumin, haptoglobin, transferrin, immunoglobulins IgG, IgA, IgM, and others.
• Enzymes: lactadehydrogenase, gamma-glutamyl transferase, alpha amylase, uropepsinogene, lysozyme, beta-N-acetylglucosaminidase, urokinase, protease, and others.
• Carbohydrates: arabinose, xyloseribose, fucose, rhammose, ketopentose, glucose, galactose, mannose, fructose, lactose, sucrose, fucosylglucose, raffinose, and others.
• Vitamins: thiamine (vitamin B1), riboflavin (vitamin B2), vitamin B6, 4-pyridoxique acid, nicotinic acid, vitamin B12, biopterine, ascorbic acid (vitamin C) and others.
• Hormones: gonadotropin, corticotropin, prolactin, lactogeniques hormones, oxytocin, vasopressin, thyroxine, catecholamines (epinephrine, norepinephrine, dopamine), insulin, erythropoietin, corticosteroids (aldosterone, corticosterone, cortisone), testosterone, progesterone, estrogen and others.
• Agglutinins and precipitines: neutralizing action on the polio virus and other viruses.
• Antineoplaston: selectively prevents the development of cancer cells without affecting healthy cells that
• Allantoin: nitrogen crystalline substance that promotes healing, from the oxidation of uric acid. It is used in the manufacture of many skin creams.
• DHEA (dehydroepiandrosterone): steroid secreted by the adrenal glands, present in large quantities in male urine. It prevents obesity, prolongs the life of animals and is a possible treatment against anemia, diabetes and breast cancer. DHEA stimulates the development of the bone marrow and increases its production of red blood cells, monocytes, macrophages and lymphocytes. A low level of DHEA seems to be associated with aging.
• Gastric antisecretory products: prevent the onset and development of stomach ulcers.
• Glucoronic acid: produced by the liver, kidneys and intestines, it has a major secretory function.
• H-11: inhibits the growth of cancer cells and reduces the existing tumors without disrupting the recovery process.
• H.U.D. HUD (Human’s urine derivative): demonstrates remarkable anticancer properties.
• Interleukin-1: a positive influence on the auxiliary and inhibitory substances. Can send a signal to the hypothalamus to trigger fever.
• Trimethyl-glyoxal: destroys cancer cells.
• Prostaglandine: a hormonal substance that dilates the blood vessels, lowers tension, relaxes the muscle walls of the bronchi, stimulates contractions during labor, and many metabolic functions.
• Proteoglobulines: plasma proteins containing anti-bodies against certain allergens, they are identical to the proteins of immoglobulines blood serum.
• Prosteoses: immunological products assets allergic reactions.

Algorithm of Common Urinary Findings

Urinary Findings

Quality (Composition)

Quantity (Volume)

Urinalysis

Urine culture

Urine output

High urine output

Low urine output

Urine odor

Color and Turbidity

Specific gravity or 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 table that lists common urine discolorations and their associated conditions.

Urine Color	Associated Conditions
Clear or Light Yellow	Normal urine color
Dark Yellow	Dehydration, vitamin B12 administration
Greenish/Yellow	Vitamin B administration
Yellow-Red	Laxatives
Orange	Rifampicin, nitrofurantoin, pyridium
Dark / Black	Alkaptonuria, porphyria, sarcoma
Milky	Lymphatic fistulas
Opaque	Bacteria, Cells
Dark Red/Pink	Concentrated, hematuria, hemoglobinuria, myoglobinuria, Ingestion of certain foods (colored candy, berries, or beets)
Yellowish-Brown	Hyperbilirubinemia
Pale	Polyuria, chronic kidney disease
Foamy or Frothy	Proteinuria
With sediment	Precipitation of urate salts
Cloudy	Pyuria, tissue components
With intestinal contents	Intestinal fistulas

To view a complete comprehensive list of causes that are are associated with urine discoloration, click here

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

• Acidosis
• Addison's Disease
• Congestive Heart Failure
• Hepatic cirrhosis
• Hypernatremia
• Shock
• Syndrome of Inappropriate Anti Diuretic Hormone (SIADH)

Decreased urine osmolality

• Aldosteronism
• Amyloidosis
• Chronic Interstitial Nephritis
• Chronic pyelonephritis
• Diabetes Insipidus
• Primary polydypsia
• Glomerulonephritis
• Hypercalcemia
• Hypokalemia
• Lithium nephrotoxicity
• Nephrogenic diabetes insipidus
• Polycystic kidneys
• Renal Tubular Necrosis

Urinary pH

• The pH of urine is normally close to neutral pH = 6 to 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

• Diabetes Mellitus
• Diarrhea
• Vomiting
• Fanconi's Syndrome
• Increased protein catabolism
• Lupus erythematosus
• Metabolic/respiratory alkalosis or acidosis
• Protein rich diet

Drug administration

• Acetazolamide
• Aldosteronism
• Amyloidosis
• Antibiotics
• Sodium acetate
• Sodium bicarbonate
• Sodium lactate

Hematuria

• Microscopic hematuria
• Gross hematuria

Pyuria

Pyuria is defined as the presence of 10 or more white cells per cubic millimeter in a urine specimen, 3 or more white cells per high-power field of unspun urine, a positive result on Gram’s stain of an unspun urine specimen, or a urinary dipstick test that is positive for leukocyte esterase

Pyuria may first be classified based on gross/microscopic examination

• Microscopic pyuria
• Gross pyuria

Pyuria may also be classified based on the presence/absence of detectable infection

• Bacteriuria (detectable bacteria in urine)
• Sterile pyuria (non-infectious cause or an infection that is undetected on regular gram-stain and urine culture)

Proteinuria

• Albuminuria
  • Microalbuminuria
  • Macroalbuminuria
• Paraproteinuria

Cells

• Benign
• Malignant

Casts and Crystals

Casts

To view a comprehensive list of urinary cast types and the characteristics of each cast type, click here

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

Eosinophiluria

• Acute interstitial nephritis
• Atheroembolic renal disease
• Rapidly progressive glomerulonephritis
• Urinary tract infection

To view a comprehensive list of causes of eosinophiluria, click here

Urinary drug concentration

• Drug testing uses urinalysis to test for certain chemicals which are typically present in the urine only after recreational drug use.
• These tests must be requested specifically or as part of a toxicology screen, and are not part of a routine urinalysis.

Dissolved electrolytes or heavy metals

Calciuria (urinary calcium) differential diagnosis:

• Bone metastases
• Diets low in calcium
• Hypervitaminosis
• Idiopathic hypercalciuria
• Increased calcium intake
• Multiple Myeloma
• Paget's Disease
• Primary hyperparathyroidism
• Prolonged immobilization
• Pseudoparahypothyroidism
• Renal Tubular Acidosis
• Renal osteodystrophy
• Sarcoidosis
• Steroids
• Vitamin D deficiency
• Vitamin D resistant ricketts

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

• Medication-induced
• Ganglioma
• Multiple endocrine neoplasia type 2
• Neuroblastoma
• Pheochromocytoma
• Stress

Urine Culture

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

• Bacteria: Bacteriuria
• Fungi: Funguria

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 Urine Output

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

Low Urine Output

Low urine output may be either oliguria or anuria:

• 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
  • 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 in adults.

For a detailed explanation of anuria, click here.

References

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