Capacity of the bladder and urination frequency

In adults, the capacity of the urinary bladder is 600-1000 ml, but the sensation of the bladder filling occurs earlier (Ernst Mutschler et al.: Mutschler Arzneimittelwirkungen, 9th edition, Wissenschaftliche Verlagsgesellschaft, 2008, p. 708). The average voiding volume (functional bladder capacity) for adults is around 300-400 ml (Lukacz E.S. et al., A healthy bladder: a consensus statement, International Journal of Clinical Practice, 2011, 65, 10, 1026-1036). The values can vary between individuals. A healthy adult eliminates approx. 1,500 mL of urine every 24 hours.
The number of urinations is also called micturition. This depends on the individual capacity of the urinary bladder and the consumed volume of liquid, among other things. An increase in micturition is to be assumed with advancing age.
At a maximum drinking volume of 2,000 mL per day, 4 - 7 urinations over the course of the day and one urination at night are considered normal.

Diagnosis in the case of urination disorders

Uroflowmetry is used as a diagnostic tool in urology to identify urination disorders. Urination disorders include frequent urination, difficulty urinating, and pain during urination.
The causes of urination disorders commonly involve an enlargement of the prostate or a narrowing of the urethra. Problems involving bladder function itself may also cause symptoms. Inadequate contraction of the bladder muscle may result in a weak urinary stream and residual urine in the bladder when the patient is unable to completely empty the bladder.

Measurement method

The measuring device, the uroflowmeter, is equipped with a funnel to collect the urine. A sensor on the tip of the funnel measures the volume of eliminated urine per time unit. The determined values are presented as a curve. The height and progression of the curve provide information concerning certain diseases.

Sequence of the examination

The urinary bladder must be full and there must be a strong urge to urinate during uroflowmetry. The bladder must contain at least 150 mL in order to provide for a meaningful assessment. During the measurement, the patient urinates in the funnel until the bladder is completely empty. Urination should take place without excessive pushing. The physician then checks to ensure whether the bladder is completely empty (residual urine measurement), usually using ultrasound.
Uroflowmetry merely involves urinating into a funnel. As a result, this test is not associated with any discomfort.

Assessment of the measurement values

The most important uroflowmetry parameter is the volume of urine measured per time unit (second) during urination.
The reference range for maximum urine flow in an adult is between 15 and 50 mL per second. Values between 10 and 15 mL per second are suspect and may potentially require more detailed study by the physician. A urine flow of less than 10 mL per second suggests an obstruction during urination.

A delayed rise in the curve and a delayed drop with prolonged urination may be a sign of an enlarged prostate. Your physician will explain your findings based on a printout of the curve.