Urine is a liquid that is excreted several times a day. It contains a host of waste substances and some excess nutrients combined with water from the body. Apart from serving as a means to expel unnecessary substances and fluid from the body, it also helps the body regulate physiological functions like blood pressure.
The kidneys produce urine by filtering the blood through tiny structures known as glomeruli. This occurs in the upper abdomen where the kidneys are located. The urine passes down the urinary bladder in the pelvis. The bladder stores the urine until it is full or if a person chooses to urinate even though the bladder is not filled to capacity.
The urethra carries this urine out of the body and into the environment. The color, volume and odor of urine along with how often urination is passed. Any abnormality in the urine or the process of urination may indicate a problem either in other parts of the body before blood is filtered in the kidneys (pre-renal), or with production of urine within the kidney (renal), the passage and storage of urine (post-renal) or discharge of urine (voiding).
Normal Urine Color, Odor and Output
Urine is known to be yellow in color but this may vary from a pale yellow to clear. A darker yellow or mustard color is not always considered abnormal but may have to be investigated at times. In some cases, urine can be discolored like a brown to black color, red, orange or even a greenish hue which may arise for several reasons, some of which are dietary while others are due to diseases.
The odor of urine is that of ammonia, resembling household detergents containing ammonia. This odor may vary in intensity. Sometimes it is barely detectable whereas other times it can be very The odor may vary after consuming certain foods (such as asparagus) or beverages (such as large amounts of coffee).
The average adult will pass out between 1 to 2 liters of urine although this can be as low as 500ml or as high as 3 liters. Frequency of urination differs among individuals and depends on the urine volume passed in a day. The frequency of urination can vary among people and is also influenced by hydration levels. Some people may only urinate 2 or 3 times in a day whereas others may urinate up to 8 times or more.
Different Types of Urinary Problems
- Anuria is the total absence of urine output or urine output less than 100ml per day. Passing urine but less than 400ml in 24 hours is known as oliguria.
- Cloudy urine refers to murky hue of the urine and indicates the presence of pus or highly alkaline urine.
- Dribbling is the involuntary passing of small amounts of urine after urination (post-micturition dribble).
- Dysuria is pain or discomfort upon passing out urine. This may vary from burning in the urethra to severe pain in the bladder, along the path of ureter or kidney pain. Also refer to urinary tract pain.
- Hematuria is the presence of blood in the urine. This may not always be obvious (visibly bloody urine) and the urine may vary between a reddish to brownish color or there may be no difference in the color and blood in the urine is only detected with testing.
- Hesitancy is difficulty initiating (starting) urination. There may be straining as the person tries to pass out urine but the onset of the urine flow is delayed.
- Incontinence is passing out urine involuntarily. This may range from dribbling to completely soiling oneself with urine.
- Nocturia is awaking at night to pass urine. Failure to do so may lead to nocturnal enuresis (incontinence).
- Oliguria is reduced urine volume output of less than 400ml per day. It should not be confused with anuria where there is little to no urine output.
- Polyuria is large urine volume output, usually more than 3 liters per day. Frequent urination does occur but frequency alone is not an indication of polyuria.
- Pneumaturia refers to gas bubbles in the urine. This may be seen with some urinary tract infections (UTIs) and should not be confused with foamy urine.
- Proteinuria is the presence of protein (particularly albumin) in the urine. This is one of the main causes of foamy urine.
- Straining is forceful effort in maintaining a normal flow of urine during urination or impaired urine flow despite straining.
- Urinary frequency or frequent urination refers to urinating more often, typically above the average number of times that a person urinates. This may vary among individuals. The volume may be small and within the norm for daily urine output or large in volume (polyuria).
Abnormalities of Urine
Urine may be considered abnormal when there are deviations of color, odor or volume of the urine. Abnormal urination may refer to straining, hesitancy, dribbling or frequent urination.
Changes in the color of the urine may not always be due to a disease. However, if the change is persistent and other signs and symptoms present then it should be investigated. The causes of these abnormal colors has been discussed under:
Although blood in the urine may not always cause red color of the urine, this has been discussed further under hematuria.
Change in the odor of the urine may be temporary and not a sign of pathology. As with changes in the color, the presence of any other signs and symptoms should be investigated further. Changes in color or odor in the event of no change in the diet, or use of medication or supplements may be an indication of poisoning or a disease.
Sometimes there may be a discharge from the urethra, vagina (women) or penis (men), which can affect the odor of urine. The presence of any discharge along with the urine may be an indication of a urinary tract infection (particularly STIs) or retrograde ejaculation in men has to be considered. Discharge should always be investigated.
Volume and Frequency
Changes in volume may not always be immediately evident. Some people may not realize that the urine that they are passing, if at all, is smaller volume than normal. Other signs and symptoms may be noticed before low or excessive urine volume output is noticed. The causes of abnormal urine volume are discussed further under:
Changes in frequency may not always be noticed immediately. Urine frequency changes even under normal circumstances with increased water consumption or with substances like alcohol or caffeine. However, frequent urination of small volume of urine should be investigated. Read more on the causes of frequent urination.