The kidneys filter the blood and produce urine: the latter is conducted by the ureters into the bladder and from here, through the urethra, to the outside with micturition. The bladder works as a reservoir that collects and keeps urine. If the bladder didn’t exist, urine would flow outside continuously since its production is continuous (even if flow varies according to the different hours of the day).
The bladder, therefore, allows the urine to be collected and eliminated when an individual decides to urinate. The mechanism which makes the bladder a reservoir, and, when necessary, allows it to empty itself, is called a sphincter.
In practical terms, the sphincter behaves like a tap which is mostly closed and opens only when we wish to empty the bladder/reservoir. Actually, the sphincter is a complex formation of both voluntary and involuntary muscular strata, which synergically keep the passage between the bladder and urethra closed. Thetightness of the sphincter is not absolute, but is relative to physiological pressure: a high pressure of urine may force its tightness. When the sphincter does not work properly, we have incontinence (leakage of urine), i.e. partial or total emptying of the bladder, without the participation and/or will of the individual.
In order to understand the causes and types of incontinence, we must remember how the bladder works. The bladder is a reservoir that adapts to its content as urine flows into it.
This reservoir is made up of involuntary smooth musculature and fills up as an elastic system (similar, for example, to a balloon), and, when it is full, it would contract and empty itself automatically if there were no control.
Physiologically, instead, when the bladder fills up with a certain amount of urine, the liquid increases its internal pressure. Since the bladder is inside the abdomen, it also receives external pressure due to muscular tension and the distention of the intestine.
Pressure receptors (indicators) positioned on the bladder wall, sensing the sum of the two pressures (internal and external), send the brain, through the nervous fibers of the spinal medulla, a message that the bladder is becoming full. The brain becomes aware that the bladder is full (sensation of fullness, the need to urinate) and, if it is impossible to urinate, the brain inhibits bladder contraction. Vice versa, when you reach the toilet, the brain removes inhibition, the bladder contracts, by reflex the sphincters open, and you can urinate. Any problem, disease or trauma interfering with this simple mechanism may cause malfunctioning and thus a leakage of urine.
We generally distinguish two types of incontinence: urge and stress incontinence, which sometimes may be associated.
Urge incontinence occurs when the bladder contracts before the brain inhibits contraction: this fact, by increasing urine pressure above the tightness of the sphincter, makes you lose your urine. The most common causes are inflammatory (cystitis) due both to bacterial or viral infections or physical damage, and neurological diseases that modify or interrupt the nervous connections between the bladder and the brain.
Stress incontinence occurs when the sphincter diminishes or loses the strengthwith which it closes the urethra: therefore, at physiological bladder filling, when the brain is not informed of the state of fullness, the increase in pressure on the bladder causes it to empty itself partially or totally.
This happens with coughing, sneezing, weight lifting, or with changes in body position: all these facts increase abdominal pressure causing a greater pressure on the bladder. If the pressure threshold to which the sphincter responds is lower than the pressure stimulating it, the sphincter does not resist and urine spills out: hence the leakage of urine.
In case of urine leakage, it is necessary to understand which type of incontinence has caused the loss of urine. Therefore, a urological evaluation is necessary, which, through an accurate reconstruction of the episodes of incontinence and the concomitant circumstances, will enable the doctor to identify the type of incontinence and find a remedy for it.
The basic tests necessary to frame the problem, besides the patient’s history and urological evaluation, are:
These tests confirm/rule out urinary tract infections, anatomical abnormalities of the urinary tract and of male and female genitalia (for example prolapses), and concomitant systemic diseases.
It is necessary to keep in mind whether the patient is in pharmacological treatment for any concomitant disorders; previous physical treatments (radiotherapy) and habits such as intestine malfunctioning must also be considered.
Sometimes, besides these basic tests, other diagnostic procedures are necessary, such as a diary of micturition and urine leakages, or a uroflowmetry. Only in particular cases and on exclusive judgement of a urologist, is it necessary to undergo a urodynamic investigation or evaluations by other specialists such as a neurologist.