Urinary Urgency: Function, Tasks, Role & Diseases

The urge to urinate corresponds to the conscious perception that the maximum filling volume of the bladder has been reached. Mechanoreceptors are located in the wall of the bladder, which register the pressure on the bladder with increasing filling level and transmit the information to the brain.

What is the urge to urinate?

The urge to urinate corresponds to the conscious perception that the maximum filling volume of the bladder has been reached. The kidneys produce up to 1.5 liters of urine daily. The urinary bladder serves as a temporary storage facility for the urine thus produced. The urine accumulates in the bladder until it is emptied by micturition. The capacity of the bladder is much smaller than the amount of urine produced daily by the kidneys. When the urine in the bladder reaches a volume of about 500 milliliters, the brain receives a notification via the nervous system and triggers the so-called urge to urinate via pressure receptors in the bladder. When the human bladder is full, the person feels a consciously perceived need to urinate through sensory cells. This need arises through a regulatory circuit of the central and autonomic nervous systems. Control over urination is not innate, but is learned by children within the first five years of life. Before gaining control, the bladder empties automatically with the urge to urinate, allowing it to reabsorb the permanently produced urine from the kidneys.

Function and task

With normal fluid intake, the urinary bladder empties through the urethra up to six times a day. The amount of urine excreted for each micturition averages around 400 milliliters. This can vary up and down depending on habit and fluid intake. The bladder has a maximum capacity corresponding to the filling volume that triggers the imperative urge to urinate or leads to involuntary bladder emptying. Between men and women, different filling volume values apply to the urge to urinate. In men, the normal value is up to 600 milliliters of filling volume until the urge to urinate becomes apparent. In women, the value is significantly lower because their sexual organs take up more space and the bladder therefore has a smaller volume. A woman’s bladder can therefore hold about 400 milliliters without the urge to urinate. There may be more or less pronounced fluctuations in these values from person to person. Confirmed maximum values do not exist. The bladder obtains its storage function from two sphincters, known as the external striated sphincter and the internal smooth sphincter. As the bladder fills, the bladder emptying muscle, Musculus detrusor vesicae, must adapt to the pressure conditions. When the muscle can no longer relax further to accommodate the increasing pressure, the steep rise in pressure shifts to the interior of the bladder. Mechanoreceptors are located in the bladder that can sense stretch and pressure. In this way, the stretch receptors in the bladder wall trigger a micturition reflex. As a consequence, the muscle emptying the bladder contracts. The internal sphincter is passively stretched and the external sphincter actively relaxes. In a circuit of the autonomic nervous system, the information about the filling level of the bladder reaches the brain via the afferent nerves of the stretch receptors and allows the person to consciously perceive the urge to urinate in this way. In the formatio reticularis, bladder emptying and urge to urinate are controlled centrally. The parasympathetic nervous system initiates the emptying of the bladder by causing the bladder muscles to contract, thus supporting bladder emptying. As its antagonist, the sympathetic nervous system causes the bladder to relax after emptying, allowing it to fill again. It stimulates the sphincter muscles to contract, preventing uninterrupted emptying of the bladder.

Diseases and ailments

In the context of various diseases, patients often suffer from increased urination. If the increased urge to urinate occurs only now and then, it is not yet a pathological phenomenon. In most cases, an increase in fluid intake or the consumption of coffee, alcohol and other diuretic substances is responsible. Equally well, the intake of diuretics or psychological stress can increase the urge to urinate. Only if there is an increased urge to urinate over a longer period of time is there possibly a disease. In this context, the urge to urinate can be described as a symptom of a disease and is not itself a disease.Symptomatically, increased urination may occur, for example, in the context of diabetes mellitus and diabetes insipidus. Stage III of acute renal failure is also characterized by increased urination. The same is true for hyposthenuria, polydipsia, and descensus uteri or prostatitis. When an obese patient is affected by increased urination, the phenomenon may be related to slackening of the pelvic floor muscles. New mothers also often suffer from slackened pelvic floor muscles and increased urination immediately after giving birth. If patients experience the urge to urinate particularly during sleep or when lying down, additional causes may be possible. For example, a bladder infection or, in men, prostatic hypertrophy can also trigger the urge to urinate. If there is an increased urge to urinate but not increased urine formation, other connections should be considered. For example, prostate disease or irritable bladder may trigger this phenomenon. In women, however, the most likely cause in this context is an early phase of pregnancy.

is an early phase of pregnancy. In addition to an increased urge to urinate, the absence of urination may also be a symptom of a disease. If the bladder empties without warning, incontinence is present and may be due to malfunctions in the nervous system regulatory circuits.