The lower urinary track consists of the urethra (the small tube that carries urine from the bladder and expels it from the body) and the bladder. The upper urinary tract consists of the ureters (two longer thin tubes that carry the urine from the kidney to the bladder) and the kidneys.
The term urination (or voiding) refers to discharge or the elimination of urine from the body.
Urine is fluid containing water and waste secreted by the kidneys. It is stored in the bladder and eliminated through the urethra. Besides waste products such as urea, uric acid, ammonia, and creatinine, it also contains a surplus of products that is necessary to the functioning of the body. In a typical urine sample sodium, potassium, calcium, magnesium, chloride, phosphate, and sulfate may be present.
The ingredients of urine are not usually visible; however, if urine is alkaline some of the ingredients may form a sediment (solid particles in solution) that can be seen in urine after voiding. If mucus or blood is present, the urine may appear to be cloudy.
Any change in urination (voiding) or in the urine itself may determine the presence of illness or disease. Urination in excess or the presence of glucose in the urine can be definitive for diabetes. Decreased urination may reflect dehydration or nephritis (inflammation within the kidneys). Hematuria (blood in urine) may also indicate kidney involvement or infestation of bladder threadworm. Suppression or absence of urine may indicate kidney failure.
If there is bladder distention and minimal urine output this may indicate an obstruction due to calculi (stones), or tumor growth. It may also occur post surgery in the recovery period depending on the type of surgery and response to anesthesia.
A urinalysis, or a testing of the urine, can often be helpful in the diagnosis and treatment of illness or disease.