Urinavgang

Urinavgang, or urination, is the act of discharging urine from the urinary bladder through the urethra. In medical terminology, the preferred terms are micturition or voiding. Urinavgang is a routine physiological function in humans and other animals with a urinary system.

The process is regulated by the autonomic and somatic nervous systems. During the storage phase, the detrusor muscle remains relaxed while the internal urethral sphincter and, if necessary, the external urethral sphincter remain closed. When voiding is initiated, signals from the sacral spinal cord and higher brain centers trigger detrusor contraction and relaxation of the sphincters. Sensory receptors in the bladder wall monitor fullness, and voluntary control over the external sphincter allows social suppression of the act when appropriate.

Normal urine output depends on age, fluid intake, and kidney function. In adults, typical voiding frequency is several times per day, and daily urine volume usually ranges from about 800 to 2000 milliliters. The bladder capacity is commonly around 400 to 600 milliliters, though this varies.

Common clinical concerns related to urinavgang include urinary incontinence, urinary retention, nocturia (nighttime voiding), dysuria (painful urination), polyuria (excessive urination), and oliguria (reduced urine output). These conditions may reflect infections, bladder outlet obstruction, neurological disorders, medications, or kidney disease. Evaluation commonly includes history, physical examination, urinalysis, and, if indicated, uroflowmetry, imaging, or urodynamic testing.