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A post-void residual urine greater than 50 ml is a significant amount of urine and increases the potential for recurring urinary tract infections. [ citation needed ] In adults older than 60 years, 50-100 ml of residual urine may remain after each voiding because of the decreased contractility of the detrusor muscle . [ 7 ]
It is a measure of the quantity of urine excreted in a specified period of time (per second or per minute). It is measured with uroflowmetry, a type of flow measurement. The letters "V" (for volume) and "Q" (a conventional symbol for flow rate) are both used as a symbol for urine flow rate. The V often has a dot , that is, V̇ ("V-dot").
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 ...
The normal number of times varies according to the age of the person. Among young children, urinating 8 to 14 times each day is typical. This decreases to 6–12 times per day for older children, and to 4–6 times per day among teenagers. [4]
The ability to voluntarily inhibit micturition develops by the age of two–three years, as control at higher levels of the central nervous system develops. In the adult, the volume of urine in the bladder that normally initiates a reflex contraction is about 300–400 millilitres (11–14 imp fl oz; 10–14 US fl oz).
The majority of fluid output occurs via the urine, approximately 1500 ml/day (approx 1.59 qt/day) in the normal adult resting state. [12] [13] Some fluid is lost through perspiration (part of the body's temperature control mechanism) and as water vapor in exhaled air. These are termed "insensible fluid losses" as they cannot be easily measured.
The urine volume is measured (this shows how efficiently the bladder empties). High volumes (180 ml) may be associated with urinary tract infections. [5] A volume of greater than 50 ml in children has been described as constituting post-void residual urine. [6] High levels can be associated with overflow incontinence.
Nocturnal polyuria is defined as an increase in urine production during the night but with a proportional decrease in daytime urine production that results in a normal 24-hour urine volume. With the 24-hour urine production within normal limits, nocturnal polyuria can be translated to having a nocturnal polyuria index (NPi) greater than 35% of ...