“I don’t know if you’ve ever wondered how the human bladder works; and if so, has this action been imagined as something simple, as the result of a routine fact of the body, conditioned by the bagging and emptying of urine?”, raises Dra. Carmen González Enguita
Urodynamic study: with the bladder open to technological scrutiny
But the divulgative concern of the head of the Urology Service at Madrid’s Hospital Universitari Fundació Jiménez Díaz does not stop there, he also outlines another argumentative line: “They knew that the process of urination is guided by our brain and that there are seasons of control at the level of the spinal cord?”
To urinate, a popular verb for the act of urination, is a very, very complex physical exercise; where the individual’s will and decision are always present.
“It is essential that a whole series of neurological circuits are intact, without any neglect, so that urination occurs in an agreed and coordinated manner after the voluntary determination of each individual”, he emphasizes.
“I think, so that they can already imagine that it is not a simple act, but a complex one, and that it is not a mechanical act either, but that the fact that it requires the action and coordination of different elements, makes the act of urinating in a complex and dynamic process“, the surgeon states with informative resoluteness.
Records and data can be obtained from these dynamic and coordinated filling and emptying actions led by the phenomena of relaxation and contraction through specific technological analyses: a urodynamic study to unravel how the patient’s bladder works.
“This is a diagnostic test that examines the functioning of the lower urinary tract (bladder and urethra), in order to observe possible changes in urination; something that would translate into some condition or subsequent illness that needs some kind of treatment”, he explains.
In the urodynamic study, the symptoms that the patient refers to in the consultation are artificially induced.
Under the ambulatory intervention system, with local anesthesia to reduce discomfort for the patient, male or female, different graphic records are obtained that indicate, among other pathologies, urinary incontinence, micturition difficulty, prolapses or pelvic pain.
And how are the bladder, urine and urination related?
The bladder has the shape of a balloon, it is a membranous smooth muscle organ – detrusor – that inflates or deflates depending on the urine content.
“As a curiosity, the term bladder comes from the Greek cistos (κύστις), so all words referring to it will begin with the root ‘cyst‘, for example, cystitiscystotomy, cystocele or cystoscopy”, explains Dra. González Enguita.
The bladder stores around 500 milliliters of urine in the case of women and 700 ml in men. People produce between 1.5 and 1.7 liters of urine each day.
The sphincter muscles open and close to empty or hold back the passage of urine into the urethra, the body’s connection to the outside.
the urine it is yellowish in color and is secreted by the kidneys as a result of the purification and filtering of the blood, the final part of the cellular metabolism and, therefore, of the functioning of all the organs of our anatomy.
The urine, which comes out of the two kidneys through the ureters, accumulates in the bladder and is expelled to the outside of the human body through the meatus of the urethra during the dynamic process of urination.
The act of urination is performed when the bladder removes the urine it contains inside: this voluntary action happens, when there is no harm, when the bag, the bladder, is full.
“Urination is very complex, involving neural circuits and impulses, receptors and neurotransmitters on the anatomical and muscular structures of both the bladder and the urethra,” the urologist points out.
It is a process with a neurohumoral foundation or compensatory mechanism led by coordinated impulses from the sympathetic nervous system (regulator of activation responses) and parasympathetic (deactivator of action).
During the filling phase, the wall of the bladder is stretched, relaxed and compliant, thanks to the action of the sympathetic nervous system; which produces the relaxation of the detrusor muscle, through Beta Adrenergic receptors, and the closure of the bladder neck due to the effect of Alpha-1 adrenergic receptors.
Inhibition of the contraction of the detrusor muscle allows the urine that arrives from the ureters to the bladder to be quietly stored without receiving any impulse to be expelled outside through the urethra.
In this phase, the bladder capacity increases without increasing the pressure or the need to initiate urination.
Some time later, you will be followed by the bladder emptying phase: the parasympathetic nervous system activates its receptors (via cholinergic stimulation) producing contractions of the detrusor muscle, the bladder.
At the same time, also by cholinergic receptors, the bladder neck and urethra are relaxed due to the inhibition of the sympathetic nervous system: the impulses necessary to facilitate the outflow of urine and empty the bladder are provoked.
Physiology of micturition
“Therefore, micturition is defined as a dynamic development, where coordination is basic and where a correct integration of the participating anatomical structures (neurological and muscular), pathways and nerve centers is necessary for everything to work properly”, he emphasizes.
“The human being achieves, within a few years of his birth, urinary continence, not losing urine involuntarily (urinary incontinence) when he does not touch the filling phase”, he adds.
“Similarly, and under equal conditions, the bladder must and must be emptied when appropriate, without micturition dysfunction occurring as a whole”, he completes.
Is there a difference between male and female urination?
Although the dynamics of urination are similar in both sexes, the anatomy of the pelvic floor in women and the prostate in men establish some differences.
The muscles and ligaments of the respective pelvic floor fulfill the function of support and stabilization of the organs that occupy the upper area of the pelvis: bladder, urethra, rectum, uterus, fallopian tubes, ovaries, vagina, prostate and seminal vesicles.
The female pelvis is wider and is structurally arranged to accompany the development of the uterus during pregnancy. The male is narrower and longer.
In women, their levator muscle complex is designed with a larger opening to accommodate the passage of the urethra and vagina (urogenital hiatus). The density of muscle fibers is lower than in men in this pelvic area.
The vast majority of cases of urinary incontinence in women are due to the involuntary relaxation of the urethral sphincter, either because of damage to the pelvic nerve or because of weakness in the muscles of the pelvic floor (the causes of which will be due to the ‘pregnancy, childbirth or menopausal stage).
The prostate, specialized in the production of fluids for semen, is crossed by the urethral duct. If the prostate enlarges, especially in the more advanced stages in men, the ureter is narrowed and the flow of urine decreases.
Conversely, urinary incontinence in men is usually linked to a radical prostatectomy.
Concludes the doctor and surgeon, Carmen González Enguita, head of the Urology Service at the Fundació Jiménez Díaz University Hospital in Madrid.
SECOND CHAPTER: ?What is and what is a urodynamic study for?? (date of publication: 09/03/2023)