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Sample of human urine

Urine, excreted by the kidneys, is a liquid containing excess water and water-soluble nitrogen-rich by-products of metabolism including urea, uric acid, and creatinine, which must be cleared from the bloodstream. Urinalysis detects these nitrogenous wastes in mammals.

In placental mammals, urine travels from the kidneys via the ureters to the bladder and exits the urethra through the penis or vulva during urination. Other vertebrates excrete urine through the cloaca.[1]

Urine plays an important role in the earth's nitrogen cycle. In balanced ecosystems, urine fertilizes the soil and thus helps plants to grow. Therefore, urine can be used as a fertilizer. Some animals mark their territories with urine.[2][3] Historically, aged or fermented urine (known as lant) was also used in gunpowder production, household cleaning, leather tanning, and textile dyeing.

Human urine and feces, called human waste or human excreta, are managed via sanitation systems. Livestock urine and feces also require proper management if the livestock population density is high.

Physiology

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Main article: Renal physiology
The chemical structure of urea

Most animals have excretory systems for elimination of soluble toxic wastes. In humans, soluble wastes are excreted primarily by the urinary system and, to a lesser extent in terms of urea, removed by perspiration.[4] In placental mammals, the urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The system produces urine by a process of filtration, reabsorption, and tubular secretion. The kidneys extract the soluble wastes from the bloodstream, as well as excess water, sugars, and a variety of other compounds. The resulting urine contains high concentrations of urea and other substances, including toxins. Urine flows from the kidneys through the ureter, bladder, and finally the urethra before passing through the urinary meatus.

Duration

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Research looking at the duration of urination in a range of mammal species found that nine larger species urinated for 21 ± 13 seconds irrespective of body size.[5] Smaller species, including rodents and bats, cannot produce steady streams of urine and instead urinate with a series of drops.[5]

Characteristics

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Quantity

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Tigers spray small quantities of urine to mark their territories.[6]
Tigers spray small quantities of urine to mark their territories.[6]

Average urine production in adult humans is around 1.4 L (0.31 imp gal; 0.37 US gal) of urine per person per day with a normal range of 0.6 to 2.6 L (0.13 to 0.57 imp gal; 0.16 to 0.69 US gal) per person per day, produced in around 6 to 8 urinations per day depending on state of hydration, activity level, environmental factors, weight, and the individual's health.[7] Producing too much or too little urine needs medical attention. Polyuria is a condition of excessive production of urine (> 2.5 L/day), oliguria when < 400 mL are produced, and anuria being < 100 mL per day.

Constituents

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Further information: Urinalysis
Urine under the microscope

About 91–96% of urine consists of water.[7] The remainder can be broadly characterized into inorganic salts, urea, organic compounds, and organic ammonium salts.[7][8] Urine also contains proteins, hormones, and a wide range of metabolites,[9] varying by what is introduced into the body.[citation needed]

The total solids in urine are on average 59 g (2.1 oz) per day per person.[9] Urea is the largest constituent of the solids, constituting more than 50% of the total. The daily volume and composition of urine varies per person based on the amount of physical exertion, environmental conditions, as well as water, salt, and protein intakes.[7] In healthy persons, urine contains very little protein and an excess is suggestive of illness, as with sugar.[9] Organic matter, in healthy persons, also is reported to at most 1.7 times more matter than minerals.[8] However, any more than that is suggestive of illness.[8]

Typical design values for the concentrations of constituents in fresh urine, based on data in Sweden and Switzerland[10]: 12 [11]
Parameter Value
pH 6.2
Total nitrogen 8,830 mg/L
Ammonium/ammonia-N 460 mg/L
Nitrate and nitrite 0.06 mg/L
Chemical oxygen demand 6,000 mg/L
Total phosphorus 800–2,000 mg/L
Potassium 2,740 mg/L
Sulphate 1,500 mg/L
Sodium 3,450 mg/L
Magnesium 120 mg/L
Chloride 4,970 mg/L
Calcium 230 mg/L

However, it is important to note that lesser amounts and concentrations of other compounds and ions are often present in urination of humans.[9]

Color

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See also: Abnormal urine color
Medical experts have long connected urine colour with certain medical conditions. A medieval chart showing the medical implications of different urine color

Urine varies in appearance, depending principally upon a body's level of hydration, interactions with drugs, compounds and pigments or dyes found in food, or diseases.[9] Normally, urine is a transparent solution ranging from colorless to amber, but is usually a pale yellow.[9] Usually urination color comes primarily from the presence of urobilin.[12] Urobilin is a final waste product resulting from the breakdown of heme from hemoglobin during the destruction of aging blood cells.[13][14]

Colorless urine indicates over-hydration. Colorless urine in drug tests can suggest an attempt to avoid detection of illicit drugs in the bloodstream through over-hydration.

  • Dark urine due to low fluid intake.
    Dark urine due to low fluid intake.
  • Dark red urine due to blood (hematuria).
    Dark red urine due to blood (hematuria).
  • Dark red urine due to choluria.
    Dark red urine due to choluria.
  • Pinkish urine due to consumption of beetroots.
    Pinkish urine due to consumption of beetroots.
  • Green urine during long term infusion of the sedative propofol.
    Green urine during long term infusion of the sedative propofol.

Odor

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Dogs communicate using olfactory signals in urine.[15]

Sometime after leaving the body, urine may acquire a strong "fish-like" odor because of contamination with bacteria that break down urea into ammonia.[citation needed] This odor is not present in fresh urine of healthy individuals; its presence may be a sign of a urinary tract infection.[citation needed]

The odor of normal human urine can reflect what has been consumed or specific diseases.[9] For example, an individual with diabetes mellitus may present a sweetened urine odor. This can be due to kidney diseases as well, such as kidney stones.[citation needed] Additionally, the presence of amino acids in urine (diagnosed as maple syrup urine disease) can cause it to smell of maple syrup.[16]

Eating asparagus can cause a strong odor reminiscent of the vegetable caused by the body's breakdown of asparagusic acid.[17] Likewise consumption of saffron, alcohol, coffee, tuna fish, and onion can result in telltale scents.[18] Particularly spicy foods can have a similar effect, as their compounds pass through the kidneys without being fully broken down before exiting the body.[19][20]


pH

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The pH normally is within the range of 5.5 to 7 with an average of 6.2.[7] In persons with hyperuricosuria, acidic urine can contribute to the formation of stones of uric acid in the kidneys, ureters, or bladder.[21] Urine pH can be monitored by a physician or at home.[22]

A diet which is high in protein from meat and dairy, as well as alcohol consumption can reduce urine pH, whilst potassium and organic acids, such as from diets high in fruit and vegetables, can increase the pH and make it more alkaline.[7]

Cranberries, popularly thought to decrease the pH of urine, have actually been shown not to acidify urine.[23] Drugs that can decrease urine pH include ammonium chloride, chlorothiazide diuretics, and methenamine mandelate.[24][25]

Density

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Human urine has a specific gravity of 1.003–1.035.[7]

Bacteria and pathogens

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Urine is not sterile, not even in the bladder,[26][27] contrary to longstanding popular belief. This opened a new area of study: the urinary microbiome. In the urethra, epithelial cells lining the urethra are colonized by facultatively anaerobic Gram-negative rod and cocci bacteria.[28] One study conducted in Nigeria isolated a total of 77 distinct bacterial strains from 100 healthy children (ages 5–11) as well as 39 strains from 33 cow urine samples, a considerable amount being pathogens.[29] Pathogens identified and their percentages were:

Bacterial isolates in human urine and cows'[29]
Humans aged 5–11 Bacterial percentage in humans Bacterial percentage in cows
Bacillus 10.4% 5.1%
Staphylococcus 2.6% 2.6%
Citrobacter 3.9% 12.8%
Klebsiella 7.8% 12.8%
Escherichia coli 36.4% 23.1%
Proteus 18.2% 23.1%
Pseudomonas 9.1% 2.6%
Salmonella 3.9% 5.1%
Shigella 7.8% 12.8%

The study also states:

Multiple antibiotic resistance (MAR) rates recorded in children urinal bacterial species were 37.5–100% (Gram-positive) and 12.5–100% (Gram-negative), while MAR among the cow urinal bacteria was 12.5–75.0% (Gram-positive) and 25.0–100% (Gram-negative).

— Microbial evaluation and public health implications of urine as alternative therapy in clinical pediatric cases: health implication of urine therapy[dead link]

Examination for medical purposes

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A Doctor Examining Urine. Trophime Bigot.

Many physicians in ancient history resorted to the inspection and examination of the urine of their patients. Hermogenes wrote about the color and other attributes of urine as indicators of certain diseases. Abdul Malik Ibn Habib of Andalusia (d. 862 AD) mentions numerous reports of urine examination throughout the Umayyad empire.[30] Diabetes mellitus got its name because the urine is plentiful and sweet.[31] The name uroscopy refers to any visual examination of the urine,[32] including microscopy, although it often refers to the aforementioned prescientific or Proto-scientific forms of urine examination. Clinical urine tests today duly note the color, turbidity, and odor of urine but also include urinalysis, which chemically analyzes the urine and quantifies its constituents. A culture of the urine is performed when a urinary tract infection is suspected, as bacteriuria without symptoms does not require treatment.[33] A microscopic examination of the urine may be helpful to identify organic or inorganic substrates and help in the diagnosis.

The color and volume of urine can be reliable indicators of hydration level. Clear and copious urine is generally a sign of adequate hydration. Dark urine is a sign of dehydration. The exception occurs when diuretics are consumed, in which case urine can be clear and copious and the person still be dehydrated.

Uses

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Further information: Lant
Urine of pregnant women in the first trimester is collected by a company which purifies the fertility hormone hCG from it (Ede, the Netherlands)

Source of medications

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Urine contains proteins and other substances that are useful for medical therapy and are ingredients in many prescription drugs. Urine from postmenopausal women is rich in gonadotropins that can yield follicle stimulating hormone and luteinizing hormone for fertility therapy.[34] One such commercial product is Pergonal.[35]

Urine from pregnant women contains enough human chorionic gonadotropins for commercial extraction and purification to produce hCG medication. Pregnant mare urine is the source of estrogens, namely Premarin.[34] Urine also contains antibodies, which can be used in diagnostic antibody tests for a range of pathogens, including HIV-1.[36]

Urine after four months of storage (note the color and turbidity change compared to fresh human urine). During storage, the urea in urine is rapidly hydrolyzed by urease, creating ammonia. Collected urine can be used as a fertilizer.
Fresh human urine after excretion

Urine can also be used to produce urokinase, which is used clinically as a thrombolytic agent.[citation needed]

Fertilizer

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This section is an excerpt from Reuse of human excreta § Urine as a fertilizer.[edit]

Applying urine as fertilizer has been called "closing the cycle of agricultural nutrient flows" or ecological sanitation or ecosan. Urine fertilizer is usually applied diluted with water because undiluted urine can chemically burn the leaves or roots of some plants, causing plant injury,[37] particularly if the soil moisture content is low. The dilution also helps to reduce odor development following application. When diluted with water (at a 1:5 ratio for container-grown annual crops with fresh growing medium each season or a 1:8 ratio for more general use), it can be applied directly to soil as a fertilizer.[38][39] The fertilization effect of urine has been found to be comparable to that of commercial nitrogen fertilizers.[40][41] Urine may contain pharmaceutical residues (environmental persistent pharmaceutical pollutants).[42] Concentrations of heavy metals such as lead, mercury, and cadmium, commonly found in sewage sludge, are much lower in urine.[43]

Typical design values for nutrients excreted with urine are: 4 kg nitrogen per person per year, 0.36 kg phosphorus per person per year and 1.0 kg potassium per person per year.[44]: 5  Based on the quantity of 1.5 L urine per day (or 550 L per year), the concentration values of macronutrients as follows: 7.3 g/L N; .67 g/L P; 1.8 g/L K.[44]: 5 [45]: 11  These are design values but the actual values vary with diet.[46][a] Urine's nutrient content, when expressed with the international fertilizer convention of N:P2O5:K2O, is approximately 7:1.5:2.2.[45][b] Since urine is rather diluted as a fertilizer compared to dry manufactured nitrogen fertilizers such as diammonium phosphate, the relative transport costs for urine are high as a lot of water needs to be transported.[45]

The general limitations to using urine as fertilizer depend mainly on the potential for buildup of excess nitrogen (due to the high ratio of that macronutrient),[38] and inorganic salts such as sodium chloride, which are also part of the wastes excreted by the renal system. Over-fertilization with urine or other nitrogen fertilizers can result in too much ammonia for plants to absorb, acidic conditions, or other phytotoxicity.[42] Important parameters to consider while fertilizing with urine include salinity tolerance of the plant, soil composition, addition of other fertilizing compounds, and quantity of rainfall or other irrigation.[48] It was reported in 1995 that urine nitrogen gaseous losses were relatively high and plant uptake lower than with labelled ammonium nitrate.[citation needed] In contrast, phosphorus was utilized at a higher rate than soluble phosphate.[49] Urine can also be used safely as a source of nitrogen in carbon-rich compost.[39]

Cleaning

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Given that urea in urine breaks down into ammonia, urine has been used for cleaning. In pre-industrial times, urine was used – in the form of lant or aged urine – as a cleaning fluid.[50] Urine was also used for whitening teeth in Ancient Rome.[51]

Gunpowder

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Main article: Potassium nitrate

Urine was used before the development of a chemical industry in the manufacture of gunpowder. Urine, a nitrogen source, was used to moisten straw or other organic material, which was kept moist and allowed to rot for several months to over a year. The resulting salts were washed from the heap with water, which was evaporated to allow collection of crude saltpeter crystals, that were usually refined before being used in making gunpowder.[52]

Survival uses

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Urophagia is the consumption of urine. Urine was consumed in several ancient cultures for various health, healing, and cosmetic purposes. People have been known to drink urine in extreme cases of water scarcity.

The US Army Field Manual advises against drinking urine for survival. The manual explains that drinking urine tends to worsen rather than relieve dehydration due to the salts in it, and that urine should not be consumed in a survival situation, even when there is no other fluid available. In hot weather survival situations, where other sources of water are not available, soaking cloth (a shirt for example) in urine and putting it on the head can help cool the body.[53]

During World War I, Germans experimented with numerous poisonous gases as weapons. After the first German chlorine gas attacks, Allied troops were supplied with masks of cotton pads that had been soaked in urine. It was believed that the ammonia in the pad neutralized the chlorine. These pads were held over the face until the soldiers could escape from the poisonous fumes.[citation needed]

Urban legend states that urine works well against jellyfish stings.[54] This scenario has appeared many times in popular culture including in the Friends episode "The One With the Jellyfish", an early episode of Survivor, as well as the films The Real Cancun (2003), The Heartbreak Kid (2007) and The Paperboy (2012). However, at best it is ineffective, and in some cases this treatment may make the injury worse.[55][56][57]

Textiles

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Urine has often been used as a mordant to help prepare textiles, especially wool, for dyeing. In the Scottish Highlands and Hebrides, the process of "waulking" (fulling) woven wool is preceded by soaking in urine, preferably infantile.[58]

Olfactory communication

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Urine plays a role in olfactory communication, since it contains semiochemicals that act as pheromones.[59][60] The urine of predator species often contains kairomones[61] that serve as a repellent against their prey species.[62]

History

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Medieval Welsh text from the Red Book of Hergest on uroscopy, called Ansoddau'r Trwnc (the 'Qualities of Urine'). Opening lines (translated):
"Since it is through the qualities of the urine that a person's faults and his dangers and his diseases and his illness can be identified..."
Image of two facing pages of the illuminated manuscript of "Isagoge", fols. 42b and 43a. On the top of the left hand page is an illuminated letter "D" – initial of De urinarum differencia negocium ('The matter of the differences of urines'). Inside the letter is a picture of a master on bench pointing at a raised flask while lecturing on the "Book on urines" of Theophilus. The right hand page is only shown in part. On its very bottom is an illuminated letter "U" – initial of Urina ergo est colamentum sanguinis ('Urine is the filtrate of the blood'). Inside the letter is a picture of a master holding up a flask while explaining the diagnostic significance of urine to a student or a patient. HMD Collection, MS E 78.

The fermentation of urine by bacteria produces a solution of ammonia; hence fermented urine was used in Classical Antiquity to wash cloth and clothing, to remove hair from hides in preparation for tanning, to serve as a mordant in dying cloth, and to remove rust from iron.[63] Ancient Romans used fermented human urine (in the form of lant) to cleanse grease stains from clothing.[64] The emperor Nero instituted a tax (Latin: vectigal urinae) on the urine industry, continued by his successor, Vespasian. The Latin saying Pecunia non olet ('money does not smell') is attributed to Vespasian – said to have been his reply to a complaint from his son about the unpleasant nature of the tax. Vespasian's name is still attached to public urinals in France (vespasiennes), Italy (vespasiani), and Romania (vespasiene).

Alchemists spent much time trying to extract gold from urine, which led to discoveries such as white phosphorus by German alchemist Hennig Brand when distilling fermented urine in 1669. In 1773 the French chemist Hilaire Rouelle discovered the organic compound urea by boiling urine dry.

Language

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The English word urine (/ˈjuːrɪn/, /ˈjɜːrɪn/) comes from the Latin urina (-ae, f.), which is cognate with ancient words in various Indo-European languages that concern water, liquid, diving, rain, and urination (for example Sanskrit varṣati meaning 'it rains' or vār meaning 'water' and Greek ourein meaning 'to urinate').[65] The onomatopoetic term piss predates the word urine, but is now considered vulgar.[66][67] Urinate was at first used mostly in medical contexts.[citation needed] Piss is also used in such colloquialisms as to piss off,[66] piss poor, and the slang expression pissing down to mean heavy rain. Euphemisms and expressions used between parents and children (such as wee, pee, number one and many others) have long existed.

Lant is a word for aged urine, originating from the Old English word hland referring to urine in general.

See also

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Notes

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Urine

View on Grokipedia
from Grokipedia
Urine is a of in humans and other vertebrates, produced by the kidneys to remove waste products, excess , and acids from the while maintaining and balance. It consists primarily of (approximately 95%), along with (about 2%), (0.1%), (0.03%), electrolytes such as , sodium, and , and various other metabolic wastes and solutes, totaling around 3,000 components. The production of urine occurs in the kidneys' nephrons through a multi-step process: is first filtered in the to form a filtrate, followed by selective of essential substances like glucose, , and most in the , and secretion of additional wastes in the distal tubule and collecting duct. Each day, the kidneys filter roughly 150 quarts (about 142 liters) of to produce 1 to 2 quarts (1 to 2 liters) of urine in adults, with output varying by age, hydration, and health status—children produce less, typically scaled to body size. Once formed, urine flows through the ureters to the for storage, where it can hold 300 to 500 milliliters comfortably before triggering the urge to urinate. Urine plays a critical role in by regulating , , and mineral levels, such as sodium, potassium, calcium, and phosphate, while its analysis—known as —provides insights into function, hydration, infections, , and other conditions through assessments of color, volume, chemical composition, and microscopic elements. Abnormalities in urine, such as changes in , protein presence, or blood cells, can signal metabolic disorders, urinary tract infections, or renal diseases.

Biology and Physiology

Formation and Production

Urine formation begins in the nephrons of the kidneys, the functional units responsible for filtering and producing urine through a series of coordinated processes. Each kidney contains approximately one million nephrons, consisting of a (glomerulus and ) and a renal tubule. The primary mechanisms involved are glomerular filtration, tubular reabsorption, and tubular secretion, which collectively transform into urine while maintaining . Glomerular filtration occurs in the , where blood enters the —a network of capillaries surrounded by . High hydrostatic pressure in the glomerular capillaries forces fluid from the across the membrane into the capsule's lumen, forming the glomerular filtrate. This filtrate includes , electrolytes such as sodium, , and ions, and small solutes like , , and , while larger molecules like proteins and blood cells are retained in the bloodstream. The process is non-selective for small molecules, with a typical filtration rate that ensures efficient waste removal without depleting essential nutrients. Following , the filtrate enters the renal tubule, where tubular recovers vital substances back into the . In the proximal convoluted tubule, about 65-70% of the filtered , , glucose, and are reabsorbed via active and mechanisms, driven by pumps on the tubular cells. The then plays a crucial role in concentrating the filtrate: the descending limb is permeable to , allowing into the hyperosmotic medullary , while the ascending limb actively transports out, creating an osmotic gradient essential for urine concentration. Further refinement occurs in the , where additional are reabsorbed, and in the collecting duct, where fine-tunes urine volume based on body needs. Tubular secretion complements by actively transporting additional substances from the into the tubular lumen, enhancing waste elimination. This process occurs primarily in the , distal tubule, and collecting duct, targeting excess ions, , , and certain drugs to maintain acid-base balance and levels. Secretion ensures that the final urine composition reflects precise adjustments to plasma conditions. Hormonal regulation orchestrates these processes to adapt urine production to physiological demands. Antidiuretic hormone (ADH), released from the in response to high or low , increases water permeability in the collecting duct via channels, promoting reabsorption and concentrating urine. Aldosterone, secreted by the , enhances sodium reabsorption and potassium secretion in the distal tubule and collecting duct, helping regulate balance and . The renin-angiotensin system, activated by low renal , triggers renin release from juxtaglomerular cells, leading to II formation, which stimulates aldosterone secretion and to conserve sodium and . Under normal conditions, adults produce 800 to 2,000 milliliters of urine per day, influenced by factors such as hydration status, dietary intake, and overall . Increased intake dilutes urine and boosts volume, while or high-protein diets elevate solute load, prompting concentration. Conditions like or disorders can alter production rates, underscoring the system's responsiveness. In mammals, evolutionary adaptations have enhanced urine concentration to conserve in terrestrial environments. The elongated and vasa recta countercurrent multiplier system allow for hyperosmotic urine production, far exceeding , which is particularly pronounced in desert-adapted species to minimize loss. This mechanism represents a key innovation in , enabling survival in arid habitats.

Excretion and Regulation

Following filtration in the kidneys, urine travels through the ureters—muscular tubes approximately 22–30 cm long and 3–4 mm in diameter that connect the renal pelvis to the bladder—via peristaltic contractions to prevent backflow. The urinary bladder, a distensible muscular sac located in the pelvis, stores urine until expulsion, with a typical capacity of 300–500 mL in healthy adults before discomfort prompts voiding. From the bladder, urine exits through the urethra, a canal that differs in length between sexes (about 4 cm in females and 20 cm in males) and is lined with smooth muscle proximally and skeletal muscle distally to facilitate controlled release. The process of urine expulsion, known as micturition or voiding, is governed by the micturition reflex, a coordinated neural mechanism that integrates sensory input from bladder stretch receptors with motor outputs to ensure efficient emptying while maintaining continence. As the bladder fills, afferent signals from pelvic nerves travel to the (primarily at S2–S4 levels), triggering a spinobulbospinal pathway that ascends to the pontine micturition center (PMC) in the for higher coordination. Upon voluntary initiation, the PMC activates parasympathetic efferents via pelvic nerves to contract the —the layer of the bladder wall—while simultaneously relaxing the (smooth muscle) and inhibiting the external urethral sphincter (skeletal muscle) through control, allowing urine to flow. This reflex is modulated by inhibitory signals from higher brain centers, such as the , to delay voiding until socially appropriate. Regulation of micturition maintains by balancing storage and elimination, primarily through the (ANS) and feedback mechanisms. During storage, sympathetic innervation from the thoracolumbar (T10–L2) via hypogastric nerves relaxes the and contracts the internal to promote continence, while parasympathetic activity is suppressed. For voiding, parasympathetic signals predominate to drive detrusor contraction and relaxation, with somatic control over the external providing fine-tuned voluntary regulation. Feedback loops involving volume sensors adjust voiding frequency to approximately 4–7 times per day in healthy adults, influenced by intake, diurnal rhythms, and hormonal factors like antidiuretic hormone; excess ingested liquid is typically processed by the kidneys and excreted as urine within 30–60 minutes to a few hours, varying by hydration status, volume consumed, and individual factors. Even without external fluid intake, the kidneys continue producing urine to eliminate toxins and metabolic waste, reducing output to a minimum of 400–500 mL per day by utilizing water from food, metabolic processes, and other internal sources. This ensures efficient waste removal without excessive strain. Disruptions in these pathways, such as from or , can impair regulation, leading to conditions like (incomplete emptying due to detrusor underactivity or outlet obstruction) or incontinence (uncontrolled leakage). Urinary incontinence, affecting continence mechanisms, is classified by underlying physiology: stress incontinence occurs with increased intra-abdominal pressure (e.g., coughing) due to urethral hypermobility or sphincter weakness, often from pelvic floor damage; urge incontinence involves sudden detrusor overactivity from involuntary reflex triggering, commonly linked to neurogenic irritation; and overflow incontinence results from chronic retention causing bladder overdistension and leakage, typically from outlet obstruction or detrusor hypoactivity, such as in nerve damage from multiple sclerosis. These disorders highlight the precision of neural and muscular coordination in normal excretion, where even minor ANS imbalances can compromise homeostasis.

Evolutionary Role

In vertebrates, urine serves as a primary mechanism for eliminating nitrogenous wastes such as and , enabling and maintenance of internal in diverse environments. This contrasts with , particularly , which employ Malpighian tubules—a system of blind-ending tubes that extract wastes from the (insect blood equivalent) and convert to for minimal water loss, reflecting adaptations to terrestrial life without a closed . The kidney, evolving from simpler structures in early chordates, represents a more complex filtration and reabsorption apparatus that processes directly, highlighting a key divergence in excretory evolution driven by habitat transitions from aquatic to terrestrial realms. Adaptations for water conservation underscore urine's evolutionary importance, particularly in terrestrial vertebrates. Mammals developed the in their nephrons, a countercurrent multiplier system that creates a hyperosmotic medullary , allowing production of concentrated urine up to four times the osmolarity of plasma to minimize in arid conditions. In contrast, aquatic species like produce dilute, hypoosmotic urine via aglomerular kidneys that prioritize excess water excretion over conservation, while marine reabsorb salts to form isotonic urine, illustrating how environmental pressures shaped urinary concentration mechanisms across vertebrate lineages. Beyond waste management, urine functions in chemical communication, enhancing and . In mammals, urinary pheromones signal estrus, with volatile compounds like major urinary proteins (MUPs) detected by the to attract mates; for instance, female mice upregulate receptors during estrus to respond to male urinary cues, synchronizing breeding cycles. Territorial marking via urine spraying in species like cats and dogs deposits signals containing fatty acids and proteins, delineating boundaries and reducing conflict by conveying identity and status to conspecifics. Fossil evidence, including urolites—trace s of urine streams manifesting as radial erosion patterns—provides insights into ancient excretory behaviors and inferred physiologies. In sauropod dinosaurs, urolites associated with trackways suggest liquid urination rather than the uric acid paste of modern birds, implying urea-based adapted to large body sizes and variable water availability, which indirectly informs dietary reconstructions by linking hydration needs to patterns. Similar traces in early fossils from deposits reveal comparable urinary signaling roles, supporting the persistence of these adaptive functions through evolutionary transitions.

Physical and Chemical Characteristics

Volume and Flow

The typical daily urine output in healthy adults ranges from 800 to 2000 milliliters, depending on factors such as fluid intake and overall hydration status. For instance, consuming 2 to 3 liters of daily can increase urine toward the upper end of this range by enhancing renal and . This output reflects the kidneys' role in maintaining , with variations occurring throughout the day due to circadian rhythms and activity levels. During micturition, or , the flow rate in healthy adults typically peaks at 20 to 25 milliliters per second in both sexes, with women often exhibiting similar or slightly higher rates due to anatomical differences in the such as its shorter length. These peak flow rates are measured via uroflowmetry and can vary based on voided volume, with higher volumes generally yielding stronger flows. Average flow rates during a single void are lower, approximately 10 to 15 milliliters per second across both sexes. Several factors can alter urine volume significantly. Diuretics such as and alcohol promote increased output by inhibiting antidiuretic hormone, leading to higher daily volumes; for example, moderate alcohol intake can increase urine output in the short term through suppression of release. Conversely, reduces volume, resulting in defined as less than 400 milliliters per day, often as an early sign of impaired renal . , exceeding 3 liters per day, commonly arises in conditions like diabetes mellitus, where induces osmotic . Urine volume varies by age and sex. In children, output is proportionally higher relative to body weight, with normal rates of 1 to 2 milliliters per kilogram per hour in infants and young children, compared to 0.5 to 1 milliliter per per hour in adults. In the elderly, volumes tend to decrease due to age-related decline in kidney function, including reduced , which can lower daily output by 20% or more even with stable intake. Sex differences are minimal for total daily volume but more pronounced in flow dynamics, as noted earlier. Clinical assessment of volume often involves 24-hour urine collection, where all voids over a full day are gathered in a to quantify total output and evaluate renal health.

Appearance and Color

Normal urine appears clear and transparent, with a color ranging from pale to deep amber, attributed to the pigment urochrome, which forms from the oxidation of during hemoglobin breakdown in the body. The intensity of this yellow hue varies with hydration status; well-hydrated individuals produce lighter, more dilute urine, while concentrates the urochrome, resulting in darker shades. Turbidity, or cloudiness, in urine deviates from its typical clarity and may stem from the presence of crystals, epithelial cells, red blood cells, or threads, often observed upon cooling or in pathological states. Foamy urine, characterized by persistent bubbles upon voiding, typically signals , where excess proteins lower and create a soap-like effect. Several factors influence urine's visual properties beyond baseline . Dietary intake, such as consuming beets, can impart a tint through , a benign discoloration from pigments. Medications like phenazopyridine, used for urinary pain relief, often turn urine orange, while rifampin, an , produces similar effects due to their metabolic byproducts. Abnormal colors frequently warrant clinical attention. Red urine commonly results from , indicating blood leakage into the urinary tract from various causes. Orange hues beyond may link to rifampin or phenazopyridine intake. Green discoloration can arise from bacterial infections or ingested dyes, altering the urine's appearance through bacterial pigments or exogenous compounds. Historically, urine color served as a diagnostic tool in ancient , with Hippocratic texts from around BCE describing observations of hues like , , or to infer humoral imbalances and predict disease outcomes. These early assessments laid foundational practices for uroscopy, emphasizing visual traits in health evaluations across Greek and Byzantine traditions.

Odor and Taste

Human urine typically exhibits a mild, aromatic primarily attributable to the presence of and , which are natural byproducts of excreted by the kidneys. This scent becomes more pronounced and ammonia-like when urine is concentrated, such as during , as lower water content amplifies the volatile compounds. Abnormal odors can signal underlying health issues or dietary influences. A sweet or fruity smell often arises from ketones in uncontrolled , where excess blood sugar leads to their production and excretion. Foul odors, resembling or rot, commonly result from bacterial overgrowth in urinary tract infections, as metabolize into stronger-smelling compounds. Additionally, consuming can produce a distinctive sulfurous due to the breakdown of its asparagusic acid into volatile sulfur metabolites excreted in urine. Similarly, coffee consumption can cause urine to smell like coffee, as volatile compounds from the roasted beans, such as furanmethanethiol, are metabolized and excreted; caffeine's diuretic effect increases urine output or concentration through mild dehydration, amplifying the odor, which is more evident with black coffee lacking additives like milk or sugar. This effect is comparable to asparagus-induced odor and is generally harmless unless excessively strong, potentially indicating high intake or inadequate hydration. The of urine is generally described as salty and bitter, stemming from its composition of electrolytes like and waste products such as , which acts as a bitter tastant. In modern contexts, tasting urine is strongly discouraged due to the risk of ingesting pathogens or contaminants that could transmit infections. Historically, however, physicians practiced uroscopy, including tasting, to diagnose conditions; for instance, the second-century physician Galen noted the sweet of urine in diabetic patients, attributing it to renal dysfunction. Urine odor can intensify post-excretion due to environmental factors. Higher temperatures accelerate the enzymatic of into , enhancing volatility, while prolonged storage allows bacterial activity to further release odorous gases.

pH, , and

The of human urine typically ranges from 4.5 to 8.0, with an average value around 6.0, reflecting its slightly acidic nature under normal conditions. A diet high in and protein tends to lower urine , making it more acidic due to increased excretion of acids like sulfuric and , while a diet rich in fruits and promotes a higher, more alkaline through greater production. Urinary tract infections can elevate above 8.0 by bacterial of into , which alkalinizes the urine. Urine density, measured as specific gravity, normally falls between 1.005 and 1.030 g/mL, serving as an indicator of solute concentration relative to . Values at the higher end of this range often signal , as reduced intake concentrates electrolytes, urea, and other solutes in the urine. Urine exhibits high solubility for key components like , which dissolves up to approximately 1000 g/L in its aqueous matrix, facilitating efficient waste elimination. However, supersaturation of less soluble substances, such as calcium and ions, can lead to formation, including stones, when their concentrations exceed limits driven by factors like low urine or pH imbalances. pH is commonly measured using dipstick tests, which provide rapid colorimetric assessment through indicator dyes that change hue based on hydrogen ion concentration. Specific gravity is accurately determined with a refractometer, which quantifies the refractive index of urine to reflect total dissolved solids. Urine pH shows diurnal variations, often becoming more acidic during nighttime hours due to circadian rhythms in acid excretion and reduced buffering from meals. Certain medications influence these properties; for instance, sodium bicarbonate administration raises urine pH by increasing bicarbonate excretion and buffering acidity.

Microbial Content

Traditionally, the human is considered sterile, with urine produced there free of microorganisms under normal conditions; however, urine samples can become contaminated during passage through the , introducing low levels of skin and periurethral flora such as species, particularly in females. Recent studies using advanced techniques like expanded quantitative urine culture (EQUC) and 16S rRNA gene sequencing have challenged this view, revealing a resident urinary in healthy individuals, composed of low-abundance, diverse bacteria including , , Gardnerella, , and , often detected via catheterized samples to minimize contamination. These microbial communities are typically non-pathogenic and may contribute to urinary tract , though their full role remains under investigation in research. As of 2025, ongoing research highlights in and recurrent UTIs, with emerging therapeutic approaches like modulation showing promise. In cases of urinary tract infections (UTIs), pathogenic bacteria predominate, with uropathogenic Escherichia coli (UPEC) accounting for approximately 80% of uncomplicated cases, followed by Klebsiella pneumoniae, Proteus mirabilis, Enterococcus species, and Staphylococcus saprophyticus. These infections often present with symptoms such as dysuria, frequency, and urgency, driven by bacterial ascension from the urethra or hematogenous spread. Antibiotic resistance is a growing concern among these pathogens, particularly extended-spectrum β-lactamase (ESBL)-producing strains of E. coli and Klebsiella, which hydrolyze multiple β-lactam antibiotics and complicate treatment, with prevalence increasing in community and hospital settings. Detection of microbial content in urine relies on standard urine culture, which grows from samples to identify pathogens and assess susceptibility, typically requiring 24-48 hours for results, and molecular methods like (PCR) for rapid DNA detection of specific or resistance genes. Asymptomatic bacteriuria (ASB), defined as significant bacteriuria without symptoms, is prevalent in certain populations, affecting 1-6% of premenopausal women, rising to 15-50% in elderly individuals (especially residents) and 2-7% in pregnant women. According to Infectious Diseases Society of America (IDSA) guidelines, screening and treatment are recommended only for pregnant women to prevent , while ASB should not be screened for or treated in most other groups, including the elderly and those with catheters, to avoid promoting resistance.

Medical Examination and Diagnostics

Urinalysis Procedures

Urinalysis procedures involve a series of standardized steps to evaluate urine for diagnostic purposes, beginning with appropriate sample collection to minimize and preserve sample integrity. The most common method is the midstream clean-catch technique, in which the patient cleans the genital area with provided wipes, voids the initial urine stream into a to discard potential contaminants, and then collects a midstream sample (typically 30-60 mL) in a sterile . Catheterization provides an alternative when clean-catch is not feasible, such as in immobile patients, by inserting a thin, sterile tube through the into the to aspirate urine directly. For assessments requiring total daily output, a 24-hour urine collection is employed, where the patient discards the first morning void and collects all subsequent urine over 24 hours in a large , often preserved with an or base to stabilize analytes. To prevent degradation of cellular elements, , or chemical components, samples should be delivered to the laboratory within one hour or refrigerated at 2-8°C if delayed, avoiding preservatives unless specified for 24-hour collections. Following collection, the procedure typically includes a macroscopic or visual examination to assess physical characteristics. A observes the urine's color, which ranges from pale yellow to in typical samples, and clarity, noting any turbidity, cloudiness, or unusual hues that may suggest the presence of cells, , or other particulates. This initial step provides a quick, non-invasive overview without requiring equipment beyond basic lighting and containers. Chemical analysis is conducted using multiparameter strips, or dipsticks, which are immersed in a well-mixed urine sample for a specified time (usually 1-2 seconds) and then evaluated for color changes indicating the presence of specific substances. These strips commonly test for glucose, , ketones, occult blood, leukocytes (via ), nitrites (suggesting bacterial reduction), , , and , with results interpreted visually or via reflectance photometry for quantitative accuracy. The process is rapid, taking about 1-2 minutes per sample, and is sensitive to concentrations as low as 5-10 mg/dL for or 75 mg/dL for glucose, depending on the strip brand. Microscopic examination focuses on the urinary sediment to identify cellular and formed elements. The urine sample (about 10-15 mL) is centrifuged at low speed (typically 400-600 g for 5 minutes) to concentrate the , the supernatant is decanted, and the remaining pellet is resuspended in a small volume of urine or saline for placement on a . Under high-power magnification (400x), the preparation is scanned systematically for red blood cells ( <3-5 per high-power field), white blood cells (<5 per field), epithelial cells, casts (hyaline, granular, or cellular), crystals (e.g., uric acid or calcium oxalate), yeast, parasites, and bacteria, with phase-contrast microscopy enhancing visibility of non-pigmented structures. This step requires fresh samples analyzed within 2 hours to avoid artifactual changes like cell lysis. In modern high-throughput laboratories, automated systems streamline urinalysis by integrating chemical and microscopic components. Flow cytometry-based analyzers, such as those using fluorescent dyes and laser detection, rapidly enumerate and classify cells, bacteria, and other particles in uncentrifuged urine by measuring light scatter and fluorescence, processing up to 100 samples per hour with reduced manual labor. These systems often combine with automated dipstick readers for comprehensive reporting, correlating well with manual methods while minimizing variability.

Diagnostic Indicators

Urine serves as a valuable diagnostic medium for detecting various biomarkers that indicate underlying health issues or physiological states. These indicators are identified through , which can reveal abnormalities in protein, glucose, blood cells, ketones, hormones, and drug metabolites. Abnormal levels or presences of these substances often signal renal dysfunction, metabolic disorders, or other systemic conditions, prompting further clinical evaluation. Proteinuria, the presence of excess protein in urine, is defined as excretion exceeding 150 mg per day and serves as an early indicator of kidney damage, such as glomerular injury or tubular dysfunction. In healthy individuals, urinary protein loss is minimal, typically under 150 mg daily, but elevated levels can result from conditions like , where proteinuria surpasses 3.5 g per day, leading to hypoalbuminemia and edema. This biomarker reflects impaired filtration barriers in the kidneys and is associated with increased cardiovascular risk. Glycosuria, or glucose in the urine, typically occurs when blood glucose levels exceed the renal threshold of approximately 180 mg/dL, as the kidneys' reabsorption capacity is overwhelmed. This is a hallmark of uncontrolled diabetes mellitus, particularly type 2, where persistent hyperglycemia leads to osmotic diuresis and potential dehydration. In non-diabetic individuals, glycosuria is rare unless renal function is compromised, such as in . Hematuria, the presence of red blood cells (RBCs) in urine, can be gross (visible, causing pink, red, or cola-colored urine) or microscopic (detectable only by microscopy, with more than 3 RBCs per high-power field). It signals potential issues like , , or malignancies such as or renal tumors, requiring imaging or for differentiation. Gross hematuria often indicates lower urinary tract bleeding, while microscopic forms may point to glomerular disease. Ketonuria, the detection of ketones like acetoacetate or beta-hydroxybutyrate in urine, arises from fat metabolism during states of insulin deficiency or reduced carbohydrate intake. It is prominent in starvation, where prolonged fasting elevates ketone production to provide energy, or in diabetic ketoacidosis associated with type 1 diabetes, where acidosis develops from unchecked lipolysis. Urine ketone levels above trace amounts warrant immediate assessment to prevent complications like coma. Urine-based pregnancy tests detect human chorionic gonadotropin (hCG), a hormone produced by the placenta shortly after implantation, using immunoassay strips that employ antibodies to bind hCG and produce a visible line. These tests are highly sensitive, detecting hCG levels as low as 25 mIU/mL in urine as early as 10-14 days post-conception. False negatives can occur if tested too early, while positives confirm pregnancy with over 99% accuracy when performed correctly. Drug screening in urine identifies metabolites of substances like cannabis, specifically 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH), which persists for days to weeks after use due to fat storage and slow elimination. Detection thresholds are typically 50 ng/mL for initial immunoassay screens, confirmed by gas chromatography-mass spectrometry at 15 ng/mL, indicating prior cannabis exposure rather than current intoxication. This biomarker is widely used in workplace and legal contexts to assess compliance or impairment history.

Pathological Conditions

Urinary tract infections (UTIs) represent one of the most common bacterial infections diagnosed through urine analysis, affecting the urinary system from the to the kidneys. Cystitis, an infection of the bladder, typically presents with symptoms such as urgency, dysuria (painful urination), frequent urination (pollakiuria), and suprapubic pain, often without systemic signs. Pyelonephritis, an upper UTI involving the kidneys, is characterized by more severe symptoms including flank pain, tenderness, high fever (>38°C), and potential or , which can lead to complications like if untreated. The lifetime prevalence of UTIs in women is approximately 50–60%, with about half of all adult women experiencing at least one episode, driven by factors like shorter length and sexual activity. Kidney stones, or urolithiasis, form when urine becomes supersaturated with minerals, leading to crystal precipitation and stone development in the kidneys or urinary tract. The most common types are calcium-based stones, comprising 75–85% of cases and primarily consisting of calcium oxalate or phosphate, while struvite stones (10–15%) arise from infections by urease-producing bacteria, resulting in alkaline urine conditions that promote rapid growth. Stone formation begins with supersaturation of solutes like calcium, oxalate, or phosphate beyond their solubility limits, followed by nucleation, aggregation, and retention within the renal pelvis or calyces. A primary symptom is renal colic, an intense, sudden flank pain radiating to the groin due to ureteral obstruction by the stone, often accompanied by hematuria, nausea, and urinary urgency. Chronic kidney disease (CKD) involves progressive loss of renal function, frequently identified through urine tests revealing proteinuria and reduced glomerular filtration rate (GFR). Proteinuria, particularly albuminuria exceeding 300 mg/g creatinine, indicates glomerular damage and accelerates CKD progression in both diabetic and nondiabetic cases, serving as a key marker for disease severity and cardiovascular risk. Reduced GFR, defined as less than 60 mL/min/1.73 m² for at least three months, reflects impaired filtration capacity and is staged from G1 (normal) to G5 (kidney failure), with progression rates varying by etiology such as 10 mL/min/year in diabetic nephropathy. GFR is commonly estimated via creatinine clearance, calculated from serum creatinine levels using equations like CKD-EPI, providing a practical surrogate when direct measurement is unavailable. Diabetes insipidus (DI), particularly the central form, results from antidiuretic hormone (ADH) deficiency, impairing the kidneys' ability to concentrate urine and leading to excessive water loss. This condition causes , with urine output often exceeding 3–20 liters per day, and produces dilute, hypotonic urine with low specific gravity (<1.005) due to unopposed renal water excretion. Accompanying drives fluid intake to match losses, and diagnosis relies on urine analysis showing persistent dilution despite , distinguishing it from osmotic diuresis in diabetes mellitus. Bladder cancer often manifests early through changes detectable in urine, with hematuria being the most common presenting sign in over 80% of cases. Gross hematuria (visible blood) correlates with more advanced disease in about one-third of patients, while microscopic hematuria prompts evaluation in high-risk individuals, yielding a diagnosis in 10–20% of such instances. plays a crucial role in by identifying exfoliated malignant urothelial cells, offering high specificity (96%) for high-grade tumors and , though sensitivity is lower (44%) for low-grade lesions. Recent advances in the 2020s have highlighted biomarkers like gelatinase-associated lipocalin (NGAL) for early detection of (AKI), a condition impacting urine output and composition. Elevated urinary NGAL levels indicate tubular damage, as seen in studies of diabetic patients on SGLT2 inhibitors, where it signals distal without proximal cortical involvement, enabling timely intervention to prevent progression to CKD. As of 2025, further developments include the updated American Urological Association/Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (AUA/SUFU) guidelines on , which provide revised risk stratification and expanded use of urine-based tumor markers for evaluation. Emerging technologies encompass rapid for urinary tract infections (UTIs) using next-generation sequencing and , as well as spectral urine analysis for non-invasive, point-of-care disease detection. Additionally, has demonstrated the potential of urine profiling to identify early-stage diseases, including cancers and infections, through patterns in cellular RNA.

Practical and Historical Uses

Agricultural and Industrial Applications

urine serves as a valuable due to its high content of essential plant s, including primarily in the form of , , and , which collectively account for approximately 90% of excreted , 50-65% of , and 50-80% of from the . In ancient civilizations such as and , urine was routinely applied to crops to enhance growth, a practice documented by Roman agronomist who recommended aged urine for fertilizing pomegranates and other plants. Today, urine-diverting toilets facilitate sustainable farming by separating urine at the source, allowing collection and storage for direct application as a nutrient-rich equivalent to synthetic alternatives, thereby reducing reliance on manufactured inputs and supporting in . In industrial applications, urine played a key role in 17th-century European production, where it was essential for extracting saltpeter () through in dedicated beds layered with lime, , and including urine and , a process overseen by royal "petremen" who collected materials from households to meet military demands. The derived from breakdown in aged urine made it an effective historically, as its alkaline properties dissolve grease and disinfect surfaces; diluted urine was used in households for removing stains from fabrics and metals, leveraging the natural ammonium hydroxide formed during decomposition. Urine also functioned as a in , particularly for processing, where its content helped fix dyes to fibers by forming coordination complexes that enhanced colorfastness, a method employed in preindustrial to prepare yarns before immersion in baths. Similarly, in leather tanning, urine was soaked with hides to loosen hair and flesh through alkaline swelling, aiding the subsequent tanning with vegetable or other agents to produce durable , a step integral to traditional production before modern chemical substitutes.) In contemporary , urine separation technologies mitigate by diverting the urine stream, which contributes up to 75% of in residential effluents, from combined systems; this reduces in water bodies and enables nutrient recovery for reuse, aligning with sustainable sanitation goals under the UN's .

Therapeutic and Survival Uses

Urine has served as a source for several historically significant therapeutic agents. , a isolated from human urine, was discovered in 1947 and developed as a thrombolytic to dissolve blood clots, offering advantages in over earlier agents like . It is purified from human male urine and administered to treat clots in the cardiovascular system or catheters. Prior to the 1940s, pregnanediol, a progesterone metabolite extracted from the urine of pregnant mares or cows, was chemically converted into progesterone for , marking an early milestone in synthesis before more efficient plant-based methods emerged. In scenarios, such as environments with limited , one's own urine has been considered for short-term hydration, as it consists of approximately 95% . However, this practice is only viable briefly and carries risks, including exacerbation of due to the urine's salt content, potential imbalances, , and further strain if repeated. Experts advise against it as a primary strategy, emphasizing that it provides minimal net gain and can worsen outcomes in prolonged . Urine therapy, or urotherapy, involves the ingestion or topical application of urine and has been promoted in for treating conditions like disorders (e.g., or eczema) and boosting immunity, based on claims of its nutrient content and properties. These assertions trace back to ancient practices but lack support from modern , with studies showing no therapeutic benefits and highlighting pseudoscientific rationales. Regulatory bodies and health organizations, including the FDA, have debunked such uses, noting potential harms like bacterial introduction or reabsorption. In field medicine and wilderness emergencies, freshly voided urine from a healthy person has been used historically as an improvised irrigant for wounds when sterile solutions are unavailable. However, urine is not sterile and modern experts, including infectious disease specialists, advise strongly against this practice due to the risk of introducing bacteria that could worsen infections; it is inferior to proper antiseptics or even boiled water where possible, with urea's antimicrobial action being limited and insufficient. Historical records, including Roman texts by Pliny the Elder, document urine's application to sores and burns for similar purposes, though contemporary guidelines prioritize safer alternatives. Myths persist regarding urine dilution techniques to evade drug testing, such as excessive intake to lower drug concentrations, but these are largely ineffective due to detection methods measuring levels, specific gravity, and temperature. Laboratories flag diluted samples, often requiring retesting under observation, and overhydration can still yield positive results if metabolites remain above thresholds. Such attempts do not reliably avoid detection and may lead to adverse consequences in employment or legal contexts.

Cultural and Symbolic Significance

In societies, urine has played a subtle role in olfactory communication, primarily through pheromones that facilitate signaling. Although humans lack a functional for detecting pheromones as prominently as other mammals, compounds in urine, such as and estratetraenol, can influence mood and social interactions at low concentrations. These volatile substances in bodily secretions like urine may modulate affective responses in others, contributing to interpersonal dynamics without conscious awareness. Across ancient cultures, urine featured in rituals tied to and . In around 1350 BCE, women suspecting would urinate on and seeds; sprouting indicated conception, with barley growth signaling a male child and wheat a female, a practice documented in the and verified as approximately 70% accurate in modern tests due to hormonal effects. This method blended ritual oracle-like prediction with early empirical observation, reflecting urine's symbolic link to life's generative forces. In some indigenous Siberian traditions, shamans incorporated urine in purification rites by filtering psychoactive mushrooms through it to enhance visionary states during spiritual ceremonies, viewing the recycled substance as a purifying medium for transcendence. Urine has long been subject to cultural taboos and etiquette norms regulating its public handling. In many Western societies, public is criminalized as ; for instance, under the UK's 1986 Public Order Act, it can result in fines up to £1,000, stemming from 19th-century concerns over public decency amid . Similarly, in the United States, ordinances in cities like New York impose fines of $50 to $250 for street , enforced since the early to maintain civic order. Gender-separated public facilities emerged in the as a response to Victorian moral codes; the first U.S. law mandating separate restrooms for men and women was passed in in 1887, with over 40 states following by 1920 to enforce sex-specific privacy and prevent perceived moral lapses. In art and literature, urine symbolizes subconscious desires and anxieties, particularly in psychoanalytic interpretations. , in (1900), analyzed urination dreams as manifestations of repressed urges, often representing release of tension or infantile regression; for example, he linked urinary symbolism to water imagery, viewing it as a disguised expression of libidinal or aggressive impulses rooted in childhood experiences. This framework influenced 20th-century literature, where urination motifs evoke vulnerability or rebellion, as seen in surrealist works exploring bodily taboos. Contemporary has repurposed urine as a provocative of defiance and bodily . In 1973, Harvard students staged the "Pee-In" against a tuition hike, marching with urine-themed signs and threatening to urinate in to symbolize rejection of institutional control. rights campaigns have similarly employed urine; in 2016, activists sang "Let Us Pee" outside the governor's mansion to oppose HB2's restrictions, highlighting enforced norms. In 2023, protesters left bottles of urine outside the to decry perceived transphobia, framing the act as a bold assertion of marginalized embodiment.

History and Terminology

Historical Discoveries

The practice of uroscopy, the examination of urine to diagnose illnesses, dates back to ancient times, with the Greek physician documenting its use around 400 BCE. He described assessing urine's color, clarity, odor, and even taste to infer imbalances in the body's four humors—, , yellow bile, and black bile—and to predict disease outcomes, such as associating pale urine with poor prognosis in certain fevers. In the , advancements in chemical analysis began to reveal urine's composition. French Hilaire-Marin Rouelle isolated from human urine in 1773 by evaporating it and treating the residue with alcohol, marking the first identification of an from a biological source. This discovery paved the way for Friedrich Wöhler's groundbreaking synthesis of in 1828, achieved by heating , which demonstrated that organic molecules could be created from inorganic materials in a setting and challenged the prevailing theory of —that living organisms possessed a unique life force necessary for such syntheses. The introduced to urine examination, enabling detailed analysis of sediments. Pioneers like Pierre François Olive Rayer and his students, including Eugène Vigla, in during the late , systematically studied urinary sediments for cells, casts, and crystals to diagnose renal diseases, with techniques spreading to Britain and by the . Alfred Donné further advanced this field through his microscopic investigations of bodily fluids, including urine, publishing illustrated works in the that highlighted pathological elements like spermatozoa and cells, establishing as a cornerstone of clinical . The 20th century brought immunological and biochemical innovations to urine testing. Following the discovery of antibiotics in the 1940s, urine cultures and sensitivity tests emerged in the 1950s to identify bacterial pathogens in urinary tract infections (UTIs) and guide antibiotic therapy, with tests for nitrites and leukocytes becoming standard by the mid-century to detect infections treatable by drugs like . In the 1960s, the development of antibody-based assays for (hCG) in urine revolutionized detection, leading to the first over-the-counter home tests by the late 1970s that allowed self-testing without laboratory animals or invasive procedures. Recent decades have leveraged to uncover the urine and its diagnostic potential. Since the , next-generation sequencing has revealed diverse bacterial communities in healthy urine, challenging the notion of sterility and linking to conditions like and UTIs, with studies identifying core taxa such as and uropathogens through metagenomic analysis. In parallel, urine-based liquid biopsies have advanced cancer detection from the onward, using techniques like cell-free and exosome profiling to identify tumor mutations and biomarkers for with high sensitivity, offering non-invasive alternatives to for early screening and monitoring.

Etymology and Linguistic Variations

The English word "urine" entered the language around the 14th century, borrowed from urine or orine (), which derives directly from Latin urina, ultimately tracing back to the ūr- or ur-, signifying "" or "liquid." This root also connects to ancient terms like vār for , highlighting urine's conceptual link to bodily fluids in early . In medical , terms related to urine often draw from Greek roots, reflecting classical influences on scientific terminology. For instance, "diuresis," denoting increased urine production or flow, originates from the 17th century via medical Latin, combining Greek dia- ("through") and ourein ("to urinate"), from ouron ("urine"). Similarly, "anuria," referring to the absence or severe reduction of urine output, emerged in 1838 as medical Latin from Greek an- ("without") + ouron ("urine") + -ia (abstract noun ). Colloquial English variations for urine include slang terms shaped by and . "Piss," a vulgar term for or urine itself, dates to around 1300 from pissier, rooted in pissiare, likely imitative of the sound of urinating. A milder , "pee," arose in 1788 as an abbreviation of "piss" (initial letter ), with the sense of "to urinate" established by 1879; it also serves as a for urine or the act. Cultural euphemisms further soften direct reference, such as "number one" for (contrasted with "number two" for ), a usage first attested in early 20th-century , possibly originating in children's or educational contexts to avoid explicitness. Across languages, terms for urine show parallels in derivation from Latin or Greek, with regional adaptations. In French, "urine" mirrors the English form, directly from Latin urina. Spanish uses "orina," an evolution from Latin urina via . In indigenous languages, the term łizh denotes urine. The linguistic treatment of urine reflects evolving taboos, transitioning from open medical discourse in antiquity—where practices like uroscopy involved detailed public examination of urine for diagnosis—to modern delicacy, fostering euphemisms amid Victorian-era prudishness that stigmatized bodily functions.

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