The act of urination. Urination disorders. Quantity, composition and properties of urine
When examining the act of urination, attention is paid to the posture of the animal during the excretion of urine, the frequency of urination, its nature and the amount of urine excreted and its appearance. Of the disorders of the act of urination, the following deserve attention.
Soreness during urination is expressed in anxiety, looking at the stomach, fanning the tail, groaning, straining, etc. (urinary colic). These phenomena can be not only during urination, but sometimes shortly before it or some time after urination. They are often observed in inflammation of the bladder, inflammation of the renal pelvis, urinary stones, spasms of the sphincter of the bladder with overflow, inflammation of the urethra or blockage of urinary stones, inflammation of the prostate or cooper glands and inflammation of the peritoneum.
Lack of urination or excretion of urine in drops with unimpaired kidney secretion and severe overflow of the bladder (ischuria). The cause of this condition may be blockage of the urethra by stones or its narrowing, paralysis or rupture of the bladder, spasm of its sphincter, and sometimes loss of consciousness. Another reason for the lack of urination may be the cessation of urine secretion by the kidneys (anuria). In this case, the urinary bladder is found empty, and in the kidneys, during their palpation, changes are found that indicate their disease.
Abnormally infrequent urination occurs due to kidney disease, accompanied by a decrease in urine secretion (oliguria), with severe diarrhea or sweating, and with a decrease in water intake.
Frequent urination occurs with and without an increase in the amount of urine excreted. Frequent urination with an increase in the amount of urine (polyuria) is associated with an increase in kidney secretion and is observed with sugar and simple diabetes, sometimes with chronic interstitial nephritis, during the recovery period with exudative processes (pleurisy, dropsy, croupous pneumonia) and with excessive fluid intake. Frequent urination without increasing the amount of urine gives them a characteristic of acute inflammation of the bladder and sometimes for pyelitis, inflammation of the urethra, prostate gland and irritation of the female genital organs. In this case, urine is usually excreted in small quantities, but often.
Urinary incontinence is the constant or intermittent involuntary release of urine without an appropriate posture and without the active participation of the animal. A similar phenomenon can be observed in paralysis of the bladder with relaxation of the 2nd sphincter due to damage to the spinal cord or bladder disease.
“There is no greater happiness in life than a bladder emptied on time” (Ovid)
“Good urination is the only pleasure that you can get without feeling remorse later” (I. Kant)
Every hour, up to about 50 ml of urine enters the bladder in a healthy adult, which gradually increases the pressure in it as the bladder fills. When the volume reaches about 400 ml, there is a feeling of filling the bubble. The urination reflex can be realized with a quantity of urine from 300 to 500 ml (depending on the anthropometric parameters of the individual). But before proceeding to the consideration of the process of urination and its regulation, it is necessary to get acquainted with the substrate of this process (from an anatomical point of view), i.e. with the bladder, or rather with its sphincters and detrusor.
The detrusor of the bladder (from the Latin “detrudere” - to push out) is the muscular membrane (of the bladder), consisting of three mutually intertwining layers that form a single muscle that expels urine - the detrusor (m. detrusor urinae). Thus, contraction of the detrusor leads to urination. The outer layer of the detrusor consists of longitudinal fibers, the middle layer consists of circular fibers, and the inner layer consists of longitudinal and transverse fibers. The most developed middle layer, which in the region of the internal opening of the urethra forms the sphincter of the bladder neck or internal sphincter ( ! note - the anatomical commonality implies a common innervation of the detrusor and the internal sphincter of the bladder, i.e. during urination, there is a simultaneous - reflex - relaxation of the internal sphincter and contraction of the bladder). It should be noted that the muscles that make up the internal sphincter of the bladder and m.detrusor urinae, consist of smooth muscle fibers that receive autonomic innervation, and therefore are not subject to consciousness. The external sphincter is located at the level of the pelvic floor and consists of striated muscles innervated by somatic nerves and, as a result, is subject to consciousness. Such conscious control is able to suppress an involuntary attempt to empty the bladder, i.e. (normally) no urine comes out until the person "consciously chooses to open the sphincter".
Quite often in modern scientific and educational literature, unfortunately, one has to deal with the statement about the presence of 2 (internal and external) bladder sphincters. The bladder does not have a single sphincter. What is called an internal “smooth muscle” sphincter is not, because it does not contain the circular muscle fibers inherent in sphincters. What is located around the internal opening of the urethra and its proximal part is a complex of anatomical formations: the tongue of the bladder "uvula vesicae" - a cavernous formation of the vesicourethral segment, a detrusor loop, bundles of longitudinal smooth muscle fibers passing from the detrusor to the urethra and transverse smooth muscle bundles of lateral sections of the proximal urethra. The blood filling of the "tongue" helps to retain urine in the bladder, the loop fixes the base plate. Longitudinal fibers during contraction shorten the proximal urethra, contributing to the opening of its internal opening before urination, and transverse fibers cause the anterior and posterior walls of the proximal urethra to close to hold urine. The "external" sphincter, which actually contains circular smooth muscle fibers, does not belong to the bladder, but is known to be the urethral sphincter.
source "Impaired bladder function (lecture)" Borisov V.V. Department of Nephrology and Hemodialysis, FPPO Physicians of the First Moscow State Medical University named after I.I. THEM. Sechenov, Moscow (journal "Bulletin of Urology" No. 1 - 2014)[read ]
quote from the clinical lecture "Peculiarities of the activity of the bladder" by V.V. Borisov:
“... A special place in ensuring the function of the bladder is occupied by the structure of small intramural vessels, which have a spiral shape. It is she who allows you to maintain the necessary constant clearance in conditions of significant stretching of the wall. In this case, the spirals are stretched, and the lumen of the arterial vessel remains unchanged. No less important in ensuring the function of the urinary tract system in general and the bladder in particular are cavernous-like vascular formations open in the wall of the ureter and bladder Yu.A. Pytel in the middle of the last century and confirmed by further studies of morphologists of the school of academician V.V. Kupriyanov. In their structure, they resemble the cavernous tissue of the penis, in which, like in a sponge, blood can be deposited, significantly increasing the volume of this formation. The sudden overflow of such a formation with blood contributes to the contraction of the surrounding smooth muscle structures and the implementation of a quick and effective overlap of the lumen of the hollow organ. Such formations have been described in the area of the ureteropelvic, ureterovesical and vesicourethral segments of the urinary tract. For the bladder, cavernous formations in the region of the ureteral orifice are one of the antireflux mechanisms during urination, and in the region of the neck of the bladder - one of the mechanisms for retaining urine in the bladder during the filling phase ... "[read the lecture in full]
In essence, the detrusor is an integral muscle, a single functional syncytium of smooth muscle cells and fibers oriented spirally in mutually perpendicular planes, fibers that pass from the inner layers to the middle and outer ones and vice versa. It is this feature of the structure that allows the detrusor to work in a friendly manner both for active expansion in the filling phase and for active contraction when emptying the bladder.
The activities of the bladder are multifaceted and include the accumulation and retention of urine, the evacuation of urine through the urethra to the outside (i.e., urination), and, last but not least, the facilitation of the flow of portions of urine from the terminal ureters and the prevention of backflow of urine from the bladder into the ureters. .
Neurogenic regulatory mechanisms of bladder activity are complex, they are elements of the autonomic nervous system and are represented in the cortex, limbic system, thalamus, hypothalamus, reticular formation, and are also associated with the cerebellum. They are connected by conducting pathways with the center of urination in the lower lumbar and sacral sections of the spinal cord. The sphincter of the urethra, with the help of the pudendal (syn.: genital) nerve, receives not only autonomic, but also somatic innervation, which determines voluntary urination.
The highest center of regulation of the entire system that controls urination is the brain, in which the urination center of the latter is located in the paracentral lobule of the frontal lobe (next to the center of the foot). The main function of the center of urination, including the frontal lobe, is ( !
voluntary, conscious) tonic inhibition of detrusor contraction until the most suitable favorable moment for emptying the bladder.
[read] the article "The role of the brain in the regulation of the process of urination" by V.B. Berdichevsky, A.A. Sufianov, V.G. Elishev, D.A. Barashin, Clinic of Urology, Tyumen State Medical Academy of the Russian Ministry of Health (Andrology and Genital Surgery Journal, No. 1, 2014)
The next center in the system of nervous control over urination is the center located in the bridge. It also has the name Barrington's core or Nucleus Locus Coerulus (the core of the bluish spot). The center is localized in the ventral part of the gray matter located around the aqueduct. In the posterior part of the bridge tire, two interacting areas are distinguished: M-zone (empty zone) and L-zone (accumulation zone). The pontine urination center plays the role of the main relay switch of afferent and efferent impulses between the brain and the lower urinary tract (bladder, urethra). It also coordinates the progressive relaxation of the urethral sphincter and the contraction of the detrusor during urination.
The lower centers (parasympathetic and sympathetic), which carry out ( ! involuntarily, unconsciously) the act of urination, located in the spinal cord. In addition, there are conductive nerve fibers in the spinal cord that connect the higher (paracentral lobules, Barrington's nuclei) and lower (spinal centers) urination. The parasympathetic urination center is located in the sacral (sacral) section of the spinal cord (in segments S2 - S4). The sympathetic center of urination is located in the thoraco-lumbar spinal cord (in segments T9-10 - L2-3). The classical concept of the activity of the bladder as a whole assumes that the filling phase (detrusor relaxation and contraction, closing of sphincters) is sympathetic, and urination (detrusor contraction and relaxation, opening of sphincters) is realized by parasympathetic structures.
somatic nerves. As mentioned above, in the spinal cord there are conducting nerve fibers connecting the higher and lower, spinal, urination centers (in the S2-4 segments), which allows arbitrary downward control over the act of urination. This "connection" is carried out by pyramidal (motor) pathways. From the spinal cord to the bladder, further connection is carried out by somatic (genital) nerves, the main point of application of which is the external sphincter; moreover, this sphincter can contract arbitrarily, but it relaxes reflexively along with the opening of the internal sphincter at the beginning of urination. Basically, the external sphincter provides retention of urine (voluntary, conscious) with increasing pressure in the bladder.
Sensitive innervation of the bladder. Afferent (going from the periphery to the center) fibers begin in receptors located in the wall of the bladder and responding to stretch. Filling the bladder reflexively increases the tone of the muscles of the bladder wall and the internal sphincter, which are innervated by neurons of the sacral segments (S2-4) and splanchnic pelvic nerves. Increased pressure on the wall of the bladder is perceived consciously, since part of the afferent impulses along the posterior cords of the spinal cord rush to the center of urination in the brainstem, which is located in the reticular formation near the bluish place. From the center of urination, impulses follow to the paracentral lobule on the medial surface of the cerebral hemispheres and to other areas of the brain.
It is assumed that in the process of evolution, the initially formed nervous system was divided into the animal and autonomic nervous systems. The animal nervous system, associated with the activity of the sense organs and voluntary skeletal muscles, ensured the adaptation of the body to the action of environmental factors. Its functions are controlled by consciousness. The autonomic nervous system, regulating the activity of internal organs, ensured the preservation of the constancy of the internal environment of the body. In response to the negative influence of external factors, it, by mobilizing the adaptive-compensatory mechanisms of the body, contributed to the performance of the functions of the animal nervous system. The activity of the autonomic nervous system was carried out without the participation of consciousness. The sympathetic part of the autonomic nervous system took over the adaptation of the body to environmental conditions. The parasympathetic part of the autonomic nervous system contributed to maintaining the constancy of the internal environment of the body. The metasympathetic part of the autonomic nervous system provided the innate automatism of the organ and was evolutionarily the most ancient part of the autonomic nervous system. The scope of its innervation is limited and covers a purely hollow organ. This autonomy of the intramural ganglia, having a complete set of links necessary for independent reflex activity - sensory, associative, effector, is, as it were, its own "brain" of the organ. The experiment shows that, having significant independence from the central and peripheral regulation, the metasympathetic nervous system is able to carry out adequate reflex activity of the organ with its complete denervation. Thus, the freshly extirpated bladder of an animal, when sufficiently filled through the urethra with warm saline, is capable of spontaneous emptying. Not all scientists are ready to recognize the separation of the metasympathetic nervous system into an independent section of the nervous system, considering it a part of the parasympathetic innervation of the bladder. However, no one denies that an organ has significant autonomous properties.
The whole mechanism of accumulation and emptying of the bladder is schematically as follows. . In the process of physiological support of the work of the lower urinary tract, the human body creates and maintains a certain tone of the striated muscles of the anterior wall of the abdomen and perineum. In these comfortable conditions, based on the presence of autonomous (involuntary, uncontrolled by consciousness) properties, the bladder slowly accumulates urine into a relaxed detrusor reservoir. The somato-visceral reflex provides the process of retention of urine received for storage through increased tone of the internal and external sphincters of the bladder, as well as the initial tone of the muscles of the perineum. The physiological tone of the striated muscles of the human body indicates the adequate functioning of the brain, within the framework of conscious control over the function of the bladder, in the conditions of adaptation of the human body to external factors of stay. The central nervous system simultaneously has a corrective effect on the work of the autonomic nervous system, which ensures the maintenance of homeostasis, including the reservoir functions of the bladder. Physiologically, bladder sympathicotonia predominates. Detrusor relaxed. Its size slowly adapts to the volume of incoming urine. In this case, the leading function of the sympathetic nervous system is the leveling of intravesical pressure by synchronously increasing the capacity of the bladder. The parasympathetic nervous system is in a depressed state. It does not send impulses to contract the detrusor and relax the internal sphincter. All systems that regulate the accumulation and retention of urine are in a state of functional equilibrium. The bladder is filled with urine to a physiologically acceptable level. Nerve impulses about this through the lateral cords of the spinal cord enter the paracentral lobes of the cerebral hemispheres, some of the impulses go to the opposite side. Conscious regulation of urination is carried out due to nerve impulses from the motor zone of the cerebral cortex to the motor neurons of the anterior horns of the S2-4 segments. In order to initiate the act of urination, the brain gives a command to the abdominal muscles to contract, and at the same time to the muscles of the external sphincter of the bladder to ensure this process is unhindered. The somato-visceral reflex is realized. This impulsation simultaneously has a triggering effect on the metasympathetic part of the bladder nervous system and a corrective effect on other autonomic centers. Sympathetic dominance fades, and the bladder comes under the influence of parasympathetic innervation. The phase of parasympathicotonia of the bladder begins. Under the influence of acetylcholine (a mediator of the parasympathetic nervous system), the detrusor contracts, the internal sphincter of the bladder relaxes. Everything happens quickly, synchronously, and the entire volume of accumulated urine leaves the bladder. The brain is informed by external control organs (hearing, vision, tactile sensations) about the completion of the act of urination. The viscero-somatic reflex induces contraction of the muscles of the perineum and relaxation of the anterior abdominal wall, with their subsequent transfer to the physiological tone mode. At the same time, the autonomous functions of the bladder are placed under the protection of the vegetative centers that accompany the new process of filling the bladder in the framework of maintaining the homeostasis of the human body.
In the living space of a person, the urinary retention system dominates, predominantly regulated by the sympathetic division of the autonomic nervous system. The conscious feeling of fullness of the bladder is mediated by the stretching of the organ wall by the increasing volume of urine during the filling phase. At the same time, sensitive impulses from receptors located in its wall enter the sacral spinal cord along the pelvic nerve. Then they are sent along the anterior and posterior columns of the spinal cord to the urination centers located in the region of the bridge and the cerebral cortex. The brain is equipped with external control organs that evaluate the current vital situation. If for a given period of time there is a suitable situation for a particular individual, then the brain, which feels the urge to urinate, initiates the beginning of the act of urination with specific actions. At the same time, the abdominal muscles, innervated by the intercostal nerves, smoothly tighten, and the muscles of the perineum relax due to efferent somatic impulses reaching the target along the pudendal nerve. This is a conscious and controlled stage of urination. Further, this somatic impulse suppresses the sympathetic dominance of the bladder, which ensures the slow accumulation of urine, and activates the parasympathetic influence on the organ through the efferent pathways of the pelvic nerve for the rapid and exhaustive emptying of the latter.
The lack of comfortable conditions for the act of urination makes a person by a volitional decision to suppress somatic impulses in the form of an urge to urinate and transmit a command of sympathetic innervation to continue the process of accumulation of urine initiated by the neurotransmitter norepinephrine. The next urge to urinate may also coincide with the lack of proper conditions. Once again, the brain suppresses the responses of the spinal cord to carry out the process of ridding the bladder of the increasing volume of urine. The urge again ceases to be relevant for human behavior. The third urge to urinate disturbs the brain at the limit of the capacity of the bladder. There are still no conditions for urination. Consciousness and upbringing do not allow the fulfillment of the demanded physiological act. However, a person feels that he can no longer resist the increasing pressure of urine on the controlled muscles of the perineum, urethra, and a powerful stream, as it were, gradually leaves the urinary tract. This is the result of an imperative urge to urinate, which, ignoring the forbidden efforts of consciousness and the forbidding coordinating influence of the autonomic nervous system, induces the autonomic metasympathetic nervous system to urgently and effectively rid the bladder of a "life-threatening" volume of urine. And only a slight blush of shame will indicate the forced disobedience of the bladder of the central and vegetative vertical of control of the nervous system.
The average daily amount of urine in a healthy person is 1500 ml. This volume is approximately 75% of the fluid taken per day, the remaining 25% is excreted from the body by the lungs, skin, and intestines. The frequency of urination per day ranges from 4 to 6 times. The bladder empties completely during urination. Urination itself lasts no more than 20 seconds at a urine flow rate of 20-25 ml/sec in women and 15-20 ml/sec in men.
Urination in a healthy person is an arbitrary act, completely dependent on consciousness. Urination begins as soon as an impulse is given from the central nervous system. Urination that has begun can be arbitrarily interrupted by an appropriate command from the central nervous system.
The physiological volume of the bladder is 250-300 ml, but depending on a number of circumstances (ambient temperature, psycho-emotional state of a person), it can vary widely.
Violations of the act of urination are divided into 2 large groups: a) disorders of the act of urination as symptoms of irritation of the lower urinary tract and b) disorders of the act of urination as symptoms of infravesical obstruction (mechanical obstruction to the outflow of urine at the level of the urethra).
Symptoms of lower urinary tract irritation include frequent and painful urination, sudden onset of an imperative (imperative) urge to urinate (a sudden strong desire to urinate, in which you sometimes fail to hold urine), frequent urination at night. Recently, these symptoms have been referred to as bladder filling phase symptoms. The cause of irritation symptoms is an inflammatory process in the bladder, prostate, and urethra. Tumors, foreign bodies, specific (tuberculous) inflammation, radiation therapy can also cause symptoms of lower urinary tract irritation.
Among the symptoms of irritation of the lower urinary tract, the most common is frequent urination - pollakiuria (daytime pollakiuria - more than 6 times in the daytime, nocturnal pollakiuria - more than 2 times per night). This symptom appears in diseases of the lower urinary tract: bladder, urethra. The volume of urine for each urination decreases, but the total amount of urine excreted per day does not exceed the norm. The frequency of urination can be significant, reaching 15-20 times a day or more. Pollakiuria may be accompanied by an imperative (imperative) urge to urinate. Pollakiuria can be noted only during the day, disappearing at night and at rest, this often occurs with stones in the bladder. Nocturnal pollakiuria (nocturia) is often observed in patients with prostate tumors. Permanent pollakiuria can be observed in chronic diseases of the bladder. Pollakiuria is often accompanied by pain during urination.
Oligakiuria- abnormally rare urination, most often the result of a violation of the innervation of the bladder at the level of the spinal cord (disease or injury).
nocturia- the predominance of nighttime diuresis over daytime due to an increase in the volume of urine excreted and the frequency of urination. Most often, this condition is observed in cardiovascular insufficiency. The latent edema formed during the day due to heart failure decreases at night when the conditions for cardiac activity improve. The intake of more fluid into the vascular bed leads to an increase in diuresis.
stranguria- Difficulty urinating, combined with frequent urination and pain. Most often, stranguria is observed in patients with a pathological process in the bladder neck and with urethral strictures.
Urinary incontinence- involuntary excretion of urine without the urge to urinate. Distinguish between true urinary incontinence and false. True urinary incontinence occurs in case of insufficiency of the urethral sphincter, while there are no anatomical changes in the urinary tract. True urinary incontinence may be permanent, or it may appear only in certain situations (intense physical activity, coughing, sneezing, laughing, etc.). False urinary incontinence is observed in cases of congenital (exstrophy of the bladder, epispadias, ectopia of the mouth of the ureter into the urethra or vagina) or acquired defects of the ureters, bladder or urethra (traumatic injuries of the urethra and ureter).
Currently, there are several types of true urinary incontinence:
stress urinary incontinence or stress urinary incontinence;
urge urinary incontinence (urinary incontinence) - involuntary loss of urine with a preceding imperative (immediate) urge to urinate;
mixed incontinence - a combination of stress and urge incontinence;
enuresis - any involuntary loss of urine;
nocturnal enuresis - loss of urine during sleep;
persistent urinary incontinence, urinary incontinence from overflow (paradoxical ischuria);
other types of urinary incontinence may be situational, for example, during sexual intercourse, laughter.
Stress incontinence. It develops as a result of a violation of the normal anatomical relationship between the bladder and the urethra due to a decrease in the tone of the pelvic floor muscles and a weakening of the sphincters of the bladder and urethra. At the same time, increased intra-abdominal pressure (laughter, coughing, lifting weights, etc.) affects only the bladder, and the urethra is beyond the action of increased pressure vectors. In this situation, the pressure in the bladder is higher than the intraurethral pressure, which is manifested by the release of urine from the urethra throughout the time until the pressure in the bladder becomes lower than the pressure in the urethra.
Urinary incontinence or urge incontinence- the inability to retain urine in the bladder when there is an urge to urinate. It is more often observed in acute cystitis, diseases of the bladder neck, prostate gland. Urinary incontinence is a manifestation of an overactive bladder.
Nocturnal enuresis- Urinary incontinence that occurs during sleep at night. It is observed in children due to neurotic disorders or intoxication due to an infectious disease, as well as due to the inferiority of the endocrine system, manifested by insufficient production of antidiuretic hormone. Under such unfavorable conditions, dissociation of impulses in the central nervous system occurs and stable connections of the cortex, subcortex and centers of the spinal cord are not formed during the formation of a reflex to urination. As a result, there is insufficient inhibition of the subcortical centers by the cortex at night and the impulses emanating from the bladder when it is filled with urine switch at the level of the spinal cord and lead to an automatic contraction of the bladder with urination, without causing the child to wake up.
Urinary incontinence from overflow. Urinary incontinence from overflow (paradoxical ischuria) occurs due to the loss of the ability of the muscles of the bladder to contract and passive overdistension of the bladder by urine. Overdistension of the bladder leads to stretching of the internal sphincter of the bladder and insufficiency of the external sphincter. In this case, there is no independent urination and urine is almost constantly excreted from the urethra drop by drop due to the excess of intravesical pressure over intraurethral. Urinary incontinence from overflow (paradoxical ischuria) is a manifestation of detrusor decompensation and occurs with infravesical obstruction of any genesis (benign prostatic hyperplasia, urethral stricture).
Symptoms of infravesical obstruction are more often manifested by symptoms of impaired bladder emptying in the form of: difficult onset of urination, the need for straining when urinating; reducing the pressure and diameter of the urine stream; sensations of incomplete emptying of the bladder after urination; acute or chronic urinary retention (involuntary cessation of the physiological emptying of the bladder); intermittent urine output.
Difficulty urinating- noted in cases of obstruction of the outflow of urine through the urethra. The stream of urine becomes lethargic, thin, the pressure of the stream weakens, up to dropping, the duration of urination increases. Difficulty urinating is noted with urethral strictures, benign hyperplasia and prostate cancer.
Urinary retention (ischuria). There are acute and chronic urinary retention. Acute urinary retention occurs suddenly. The patient cannot urinate with intense urge to urinate and intense pain in the bladder area. Acute urinary retention often occurs in cases of existing chronic obstruction of the outflow of urine (benign prostatic hyperplasia, stone and urethral stricture).
Chronic urinary retention develops in patients with a partial obstruction to the outflow of urine in the urethra. In these cases, the bladder is not completely emptied of urine during urination and part of it remains in the bladder (residual urine). In healthy individuals, after urination, no more than 15-20 ml of urine remains in the bladder. With chronic urinary retention, the amount of residual urine increases to 100, 200 ml or more.
The act of urination consists of two phases - the phase of accumulation of urine and the phase of evacuation of urine. At the same time, the detrusor of the bladder and its sphincters (smooth muscle and external, striated) are in reciprocal relationships: in the phase of urine accumulation, the detrusor relaxes, and the sphincter is contracted and retains urine, in the phase of urine emptying, the detrusor contracts and the sphincter relaxes, the bladder is emptied. This process is provided by a complex regulatory system, which involves the spinal cord, subcortical and cortical centers, a system of biologically active substances and sex hormones.
In the urine accumulation phase, the main role belongs to the bladder detrusor, which provides an adequate reservoir function (due to the elasticity of the bladder muscles and thanks to the system of detrusor-stabilizing reflexes), while the pressure in the bladder, despite its filling, is maintained at a low level (5 -10 cm water column). Urinary evacuation is a complex reflex act, during which there is a synchronous relaxation of the internal and external sphincters of the bladder and contraction of the bladder muscle-detrusor. The abdominal and perineal muscles also take part in the evacuation of urine. Normal urination is determined by the anatomical and functional usefulness not only of the sphincters and detrusor, but also by the system of nervous structures that regulate this complex act.
The main autonomic center is the spinal center of regulation of the act of urination, located at the level of the lumbosacral segments of the spinal cord, which, in turn, has sympathetic (Th XII - L II-III) and parasympathetic (LIV-V) representation. It should be remembered that the parasympathetic department is responsible for the vegetative provision of the contractile activity of the detrusor, and the sympathetic department is responsible for its adaptation (as the bladder fills with urine, the pressure in it does not increase). Somatic provision of the striated muscles of the pelvic floor is provided by the sacral segments. But the connection between the somatic and vegetative links is largely carried out thanks to the system of reflexes stabilizing the detrusor. It is thanks to this complex system that the reciprocal relationship between the detrusor and the sphincter is ensured (when the detrusor contracts, the sphincter relaxes, and, conversely, the cessation of urination and the contraction of the sphincter leads to the restoration of the reservoir function of the bladder). From 6-8 months to one year, the child begins to feel and tries to somehow “signal” the need to urinate. There is an active formation of a conditioned reflex, cortico-visceral (vertical) connections are formed, carried out through subcortical, pontine centers. As the child grows older, in instilling the skills of urination and the formation of a mature type of control over it, three main factors become especially important:
1. Increasing the capacity of the bladder to ensure its reservoir function.
2. The emergence of arbitrary control over the striated muscles (external urethral sphincter) to ensure the arbitrary start and end of the act of urination, which usually appears by the third year of a child's life.
3. Formation of direct voluntary control over the micturition reflex, which allows the child to control the process of detrusor contraction by his own volitional effort. Initially, the possibility of control manifests itself in the daytime, and later during sleep. The last phase of developing urinary control is the most difficult. The formed mechanism of control over the micturition reflex, similar to an adult, in most children develops by the age of 5. It is also characterized by the absence of involuntary detrusor contractions in the accumulation phase, which is also confirmed by special urodynamic studies.
Thus, given the complexity and multicomponent nature of the regulatory mechanisms of the act of urination, one can imagine how diverse the etiopathogenesis of urinary incontinence in children can be. Nevertheless, if you follow the diagnostic protocol developed on the basis of the recommendations of the International Society for Urinary Continence in Children, you can, after conducting the necessary research, clearly differentiate the differences in the causes and nature of urinary incontinence, prescribe a pathogenetically justified treatment, conduct a course of rehabilitation and achieve recovery.
The act of urination
The final urine from the renal pelvis through the ureters enters the bladder. In a filled bladder, urine exerts pressure on its walls, irritating the mechanoreceptors of the mucous membrane. The resulting impulses along the afferent (sensory) nerve fibers enter the urination center located in the 2-4 sacral segments of the spinal cord, and then to the cerebral cortex, where there is a feeling of urge to urinate. From here, impulses along the efferent (motor) fibers come to the sphincter of the urethra and urination occurs. The cerebral cortex is involved in voluntary urinary retention. In children, this cortical control is absent and is developed with age.
Quantity, composition and properties of urine
Amount of urine
The difference between the amount of fluid drunk and excreted is called diuresis (it must be counted). Normally, in an adult, the daily amount of urine is 1.5 - 2 liters.
An increased amount of urine is normally noted with heavy drinking, as well as with chills, since spasm of the skin vessels increases blood flow to the kidneys.
A pathological increase in diuresis is called polyuria - observed in diabetes mellitus (due to an increase in the osmotic pressure of primary urine due to the high content of glucose in it), inflammatory diseases of the kidneys, water metabolism disorders, hyperfunction of the thyroid gland, diabetes insipidus (associated with a decrease in the production of vasopressin) .
A decrease in the amount of urine is normally observed during a dry diet, as well as during heat and during physical exertion, which is explained by increased sweating.
A pathological decrease in diuresis is called oliguria, and a complete cessation of urination is called anuria. Oliguria and anuria are observed in nephrosclerosis, chronic glomerulonephritis, chronic renal failure, closing of the lumen of the ureter with a stone or compression of the urethra by a hypertrophied prostate gland (with adenoma and prostate cancer), after heavy blood loss (due to a drop in hydrostatic blood pressure), hypothyroidism, with an excess of the hormone vasopressin.
