Urine

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Introduction[edit | edit source]

Urine chart dehydration.jpg

Urine is a liquid waste produced by the kidneys. Urine is a clear, transparent fluid that normally has an amber color. The average amount of urine excreted in 24 hours is between 5 to 8 cups or 40 and 60 ounces. Chemically, urine is mainly a watery solution of salt and substances called urea and uric acid.

  • Normally, it contains about 960 parts water to 40 parts solid matter.
  • Abnormally, it may contain sugar (in diabetes), albumin (a protein, as in some forms of kidney disease), bile pigments (as in jaundice), or abnormal quantities of one or another of its normal components.[1]

The kidneys make urine by filtering wastes and extra water from the blood. The waste is called urea. Your blood carries it to the kidneys. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The bladder stores urine until the person is ready to urinate. It swells into a round shape when it is full and gets smaller when empty. If your urinary system is healthy, the bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours

Characteristics[edit | edit source]

  • Urine Osmolarity: The urine osmolarity is a way to assess the concentration of the urine and may vary between 50 and 1200 mOsmol/kg. on average, urinary solute comes to about 1000 mOsmol/ day, with approximately 1.4 liters of urine being secreted per day. The amount and concentration of urine varies with the level of exertion, the environment, the level of hydration, and the intake of salt and protein. The solute concentration is higher in meat-eaters, because of the large amount of urea obtained from meat, whereas lower solutes are formed in vegetarians who get most of their energy from carbohydrates[2]
  • pH: normally around 6.2 with a range of 5.5–7.0.  A high dietary protein and alcohol intake leads to increased pH, while vegetables and fruit bring about a more alkaline pH.[2]
  • Contents. Over 99 percent of urinary solutes are composed of only 68 chemicals which have a concentration of 10 mg/L or more. 42 compounds are actually involved. They may be classified as follows: Electrolytes such as sodium, potassium, calcium, magnesium and chloride; Nitrogenous chemicals such as urea and creatinine; Vitamins; Hormones; Organic acids such as uric acid; Other organic compounds.[2]
  • Total Dissolved Solids: constitute between 24.8 to 37.1 g/kg. Urinary solids are primarily made up of organic matter, largely volatile solids. Urine has large amounts of nitrogen, phosphorus, and potassium. Nitrogen content in urine is high, mostly in urea, which makes up more than 50 percent of the total organic acids. This includes urea from protein metabolism, sodium and potassium both of which come from food. Dry solids thus comprise 14-18 percent nitrogen, 13 percent carbon, and 3.7 percent each of potassium and phosphorus. The largest excretion of these substances from the body is through urine[2]
  • Nitrogen in urine is excreted mostly as urea, with about 11 g per day being the average excretion of nitrogen. Creatinine is another important nitrogenous compound in urine, and its level depends on the body mass and muscle mass, as well as age. Nitrate is a third nitrogenous compound in urine, with increased concentrations if the person has a high protein diet.[2]

Urinalysis[edit | edit source]

Urine is an unstable fluid; it changes composition as soon as it is eliminated through micturition. Accurate collection, storage, and handling are crucial to maintaining the sample’s integrity.

Urinalysis is an ancient diagnostic screening test that has stood the test of time and is still useful in clinical laboratories since it plays a critical role in the health assessment process. For some, a urinalysis is considered as the most common, simple, and relevant screening exam that provides clinicians with valuable information about the general health status of a patient, including hydration, urinary tract infection, diabetes mellitus, and liver or renal disease.[3]

Clinical Significance[edit | edit source]

Kidney anatomy.jpg

A person may have problems with urination if you have

References[edit | edit source]

  1. Medicine Net Urine Available:https://www.medicinenet.com/urine/definition.htm (accessed 9.7.2021)
  2. 2.0 2.1 2.2 2.3 2.4 Medical Live Science Urine Available:https://www.news-medical.net/health/Urine-Composition-Whats-Normal.aspx ( accessed 9.7.2021)
  3. Queremel Milani DA, Jialal I. Urinalysis. [Updated 2021 May 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available: https://www.ncbi.nlm.nih.gov/books/NBK557685/ (accessed 9.7.2021)
  4. Midline plus Urine Available:https://medlineplus.gov/urineandurination.html (accessed 9.7.2021)