Cystometry

Cystometry is the basic method of urodynamic studies, during which both phases of the urination cycle are studied - filling (accumulation) and emptying, studying the dependence of intravesical pressure on the degree of filling of the bladder. Cystometry allows you to assess the function of the detrusor and urethra at different periods. So, normally in the filling phase, the bladder does not contract and is passive, and the urethra is closed (shortened). In the emptying phase, the bladder contracts, and the urethra relaxes, which ensures a normal flow of urine. Filling is assessed from the point of view of sensitivity, capacity, stability of compliance and competence: that is, explore both the motor / motor and sensitive components of the urinary reflex.

Cystometry is an invasive study. Prior to its implementation, study the medical history, conduct a physical examination, assess the diary of urination and the results of a general urine test. A physical examination for specificity can be called neuro-urological and urogynecological. Define some reflexes (anal, bulbous-cavernous), cognitive function. For women, a vaginal examination is required, an assessment of the pelvic floor muscles, as well as a Q-tip or a direct catheter test to determine urethral mobility, a test with pads). For men, a digital rectal examination, and if necessary - ultrasound (ultrasound) of the prostate.

Indications for cystometry

• pollakiuria,
• nocturia,
• Urgency urge to urinate,
• enuresis,
• difficulties in "starting" urination,
• urinary incontinence,
• the presence of residual urine in the bladder (retention),
• dysuria in the absence of an inflammatory process in the urinary system.

The main evaluation criteria for cystometry

Criterion	Characteristic
Sensitivity	Subjective sensation arising when filling the bladder. Determine from the moment of the first sensation of filling to a strong urge
"Stability" (in the old terminology) or the absence of involuntary detrusor cuts	During the filling phase, the bladder is inhibited and does not contract. Urination begins with an arbitrarily initiated detrusor reduction
Compliance	The property of the bladder is to keep the low intraluminal pressure at various volumes of its filling. Determine by the formula C = V / P detrusor (ml / cm of water)
Capacity	Cystometric - the volume of the bladder, which is commanded to urinate. Maximum cystometric - the volume at which the patient can no longer hold the urge to urinate
Competence (urethra)	The ability to maintain and, if necessary, increase the pressure in the closure area, ensuring a constant difference in urethral and papillary pressure in its favor (ensuring the retention of urine during filling)

Cystometry can be simple single-channel, when only intravesical pressure is recorded. Such a study is carried out in two modes: intermittent. When the filling of the bladder with sterile solution / water alternates with pressure recording periods (a single-channel catheter is used), or permanent, when filling and recording is carried out simultaneously (using a two-channel catheter).

At the moment, two-channel cystometry is considered the standard, when the indicators of intravesical and intra-abdominal pressure are simultaneously recorded. A two-channel catheter is used to measure intravesical pressure (usually 6 to 10 CH) and a rectal balloon catheter to measure intra-abdominal pressure.

You can use catheters filled with water, air, and "micro-type" catheters, with a piezo-electronic sensor at the end. The most widely available and widely used water catheters. In the future, it is possible to switch to air or "microtype" catheters, which provide more accurate measurements, free from the influence of the hydrostatic component. Catheters are connected to pressure sensors and a computer system that records the readings. The study is carried out in a standing, sitting or lying position. Pressure sensors must be located at the level of the pubic articulation. In expert-class laboratories, the number of measurement channels is sometimes increased to six, combining cystometry with EMG and constant X-ray control (video-dynamic study).

The International Continence Society (ISC) recommends a minimum list of requirements for equipment for cystometry:

• two channels of pressure measurement with display and safe preservation of three pressure indicators (vesicou, abdominal, detrusor);
• one channel measuring urine flow with display and storage of information;
• registration of indicators of the entered volume and volume of the allocated urine (in graphic and digital form);
• adequate scales and measurement scales without loss of information beyond the limits of the scale;
• accounting of the standard information record.

Method of cystometry

The study begins with the placement of the patient in the chair or on the "field" treatment couch, the installation of catheters, connecting them to the sensors, checking the adequacy of their work. The bladder should be empty. For stationary urodynamics, the filling is carried out at a rate of 10-100 ml / min (depending on the age of the patient and the capacity of the bladder). Outpatient urodynamic research involves the natural filling of the bladder. The volume of filling is calculated according to the capacity: for adults - 400-500 ml. For children - according to the formula 30 + 30p, where n is the age of the patient in years.

During filling, the sensations of the patient, the pressure and volume parameters are recorded. The main parameters recorded during urination (cystometry of emptying) are pressure, flow rate and volume. When researching on the chart, mark the main events:

• cough to confirm that the pressure transmission is OK (conducted at the beginning, at the end and every 100 ml of filling):
• beginning of infusion;
• first sensation;
• the first urge to urinate;
• normal urge to urinate;
• strong urge to urinate;
• Spontaneous and provoked by coughing or straining of leakage of urine;
• maximum cystometric capacity;
• stop infusion and start urination;
• nonspecific sensations, pain, urgency;
• artifacts (can be commented).

In the study report, all events should be detailed according to the pressure indicators of all registration channels and the volume of filling at the time of the event.

Explanation of results

Urodynamic disorders, determined by cystometry:

• hypersensitivity - the emergence in the early stages of filling the first sensation or urge, a strong prolonged urge to urinate;
• reduced sensitivity 
• reduced sensitivity during filling;
• lack of sensitivity - during the entire phase of filling the bladder, there is no sensitivity;
• decreased compliance - a violation of the ability to maintain low intravesical pressure during filling, which leads to a decrease in the cystometric capacity;
• detrusor hyperactivity - involuntary detrusor pressure rises of various amplitude. It can be neurogenic (neurological cause) and ideopathic. For neurogenic detrusor hyperactivity, a higher amplitude of contractions is characteristic, 
• urinary incontinence due to detrusor hyperactivity (mandatory urinary incontinence):  
• stress urinary incontinence: loss of urine due to increased abdominal / intra-abdominal pressure:
• IVO-increase of detrusor's detonation pressure and decrease in flow rate during synchronous registration (standardized only for men for women, clear criteria have not yet been determined). IVO is often due to an increase in the prostate gland in men, prolapse of pelvic organs in women (see "Pressure-flow ratio study");
• dysfunctional urination (pseudodissinergia) uncoordinated relaxation of pelvic floor muscles and reduction of detrusor during urination in the absence of a neurological disorder, which leads to a violation of emptying the bladder. To diagnose such a disorder, cystometry is combined with EMG of pelvic floor muscles;
• detrusor-sphincter dissynergy - a competitive reduction in detrusor reduction in the urethra and periurethral striated muscles, recorded during emptying. In this case, the flow of urine can be interrupted. Determine only in patients with spinal cord injuries. To diagnose detrusor-sphincter dissynergy, cystometry is supplemented with EMG and / or conducted in the framework of video-dynamic examination.

Thus, cystometry is of great clinical importance, since it helps to correctly interpret the symptoms of urinary disorders and choose the most effective type of treatment.

[1], [2], [3], [4], [5]

Pressure / flow ratio study

It consists in measuring intravesical pressure, intra-abdominal pressure and volumetric flow rate during the entire phase of urination. The study is used to analyze the violation of emptying and determine its cause (actually an IVO or a violation of the contractile capacity of the bladder).

From the point of view of the physiology of urination, it is believed that the urine flow collects speed when detrusor pressure begins to exceed the urethral pressure. This value is called the opening pressure of the urethra (P _det, open). Further, the flow rate reaches its maximum (Qmax), which is determined by the ratio between the detrusor and urethra pressure. As soon as the detrusor pressure ceases to exceed the pressure in the urethra, the urinary bladder is no longer able to expel the urine, and the flow rate becomes zero.

A full emptying of the bladder is provided by three components:

• sufficient amplitude and duration of detrusor reduction;
• adequate and timely reduction of urethral resistance (opening of the sphincter);
• absence of mechanical obstruction.

In addition, to assess the coordination of pelvic floor muscles and detrusor cuts, it is possible to perform EMG, according to special indications - video-dynamic study.

The flow / volume ratio study is performed after the filling cystometry, when the patient expresses a desire to urinate, and the filling of the bladder ceases. The recommended size of the catheter is 7-8 CH, so as not to create an additional obstacle to the flow of urine. The Urofluometer is placed as close as possible to the external opening of the urethra for recording the flow without artificial delay. The study is conducted in the most comfortable conditions, without external stimuli and provocations. The following indicators are used for interpretation:

• intravesical pressure - Pves (mm.v.st.);
• abdominal / intra-abdominal pressure - Pabd (mm.v.st.);
• detrusornoe pressure - Pdet (mm.v.st.)
• maximum detrusor pressure (cmW.water);
• detrusor pressure at the maximum flow (cm Hg);
• volume of residual urine.

A flux / volume ratio study is the only way to separate men with low Qmax due to impaired detrusor function from patients with true IVO. In this case, the presence of IVO is indicated by low Qmax values against a background of high intravesical pressure. On the other hand. The combination of low intravesical pressure with relatively high Qmax indicates a non-obstructive urination. In patients with low values of intravesical pressure and Qmax, a violation of the detrusor contractile capacity may be suspected: primary or conditioned IVO.

For the convenience of assessing the parameters of obstruction and contractility, a large number of nomograms has been proposed. The most commonly used are two of them.

Nomogram Abrams-Griffiths (1979). To build it, the authors used pressure / flow ratio charts to identify patients with IVO. Nomopharma allows to define urination as obstructive (high pressure, low speed), non-obstructive (low pressure and high speed) or as ambiguous. The boundaries between the three zones of nomophram were determined empirically.

The nomograph Schafer (1985) is an alternative method of interpreting the degree of obstruction. The author uses the same basic principles as when creating the Abrams-Griffiths nomogram. The pressure / flow ratio was evaluated taking into account the concept of elasticity and stretchability of the urethra. The conducted analysis allowed introducing the concept of "passive urethral resistance", quantitatively interpreting the pressure / flow data. Passive urethral resistance is defined as the ratio of the minimum opening pressure of the urethra and the constant C. These parameters reflect the optimal conditions of urinary outflow from the bladder for this act of urination with a relaxed state of the urethra and the smallest possible urethral resistance. The location of the graph and the shape of the loop of the linear ratio of the passive resistance of the urethra depend on the nature and degree of obstruction. By transferring a simplified pressure / flow chart to the nomogram, it became possible to assess the degree of obstruction on a 7-point scale (0 to VI). Comparison of the proposed methods with a clinical assessment of obstruction showed their complete coincidence, which proves the validity of the underlying theoretical premises.

The urine flow / volume ratio is standardized only for men, to assess the urinary function of which nomograms were created. Approaches to assessing obstruction in women are under development. At the moment, the following urodynamic criteria serve to determine female obstruction: Pdet / Qmax> 35 cm of water. At Qmax <15 ml / s.

When examining men, the urine flow / volume ratio is the "gold standard". Timely determination of the nature of urodynamic disorders (primarily IVO) is of practical importance in the treatment of patients with prostate adenoma, since without this factor, the functional results of surgical treatment deteriorate substantially. It is estimated that about 25-30% of patients referred for surgery on the results of a comprehensive survey meet urodynamic criteria for obstruction associated with prostate disease, and up to 30% of patients with reduced detrusor contractility without signs of obstruction are promptly treated.

At the moment, the European Association of Urology has developed rigorous indications for a flow / volume study in patients who are planning an operative intervention for prostate adenoma:

• age less than 50 years;
• age over 80 years;
• the volume of residual urine is more than 300 ml;
• Qmax> 15ml / s;
• suspicion of neurogenic dysfunction;
• the transferred radical operative intervention on pelvic organs;
• at unsatisfactory results of previous surgical treatment

It is proposed to add to the list of indications an additional item - the incompatibility of the level of complaints (using the international system of summary assessment of prostatic disease symptoms (IPSS)] and the data of primary uroflowmetric screening (expressed complaints and minor urination disorders or minor complaints with pronounced urination disorders determined by uroflowmetry).

Combined urodynamic examination is also recommended for patients with concomitant diabetes mellitus, before planned surgical or minimally invasive treatment. Timely conduct of the flow / volume study significantly improves the results of surgical treatment, allows to avoid diagnostic errors and, thereby, raise the quality of life of patients.

Investigation of "pressure at the point of leakage"

Conducted in patients with insufficient obstructive function of the urethra for various reasons. Allocate abdominal and detrusor pressure at the point of leakage. Abdominal pressure is measured by coughing or straining. The measurement is more preferable when straining, as it is necessary to determine the minimum pressure leading to leakage. With a cough test, the amplitude is usually higher than the minimum required. The most important parameter is detrusor pressure, when leakage of urine occurs due to an increase in detrusor pressure without "stressful" provocation or straining. Measured at the beginning of urination / leakage, the intravesical pressure is defined as the opening pressure.

In patients with IVO, this indicator is quite high. In a number of observations with obstruction, the detrusor pressure exceeds 80 cm of water. (one of the IWO indicators). In this situation, this is a reflection of the urethral resistance, and not a characteristic of the retention function. Patients with pathologically high detrusor leakage may simultaneously have a low abdominal pressure index. Men with damage to the transverse striated sphincter (for example, after radical prostatectomy) have a low detrusor pressure at the point of leakage, as well as healthy women with a short, easily open urethra. Thus, according to this indicator, it is difficult to judge the function of the detrusor itself.

The clinical meaning of determining detrusor pressure at the point of leakage is to predict the situation in the upper urinary tract with simultaneous presence of obstruction (more often than functional) and urinary incontinence in persons with neurogenic disorders of urination. In such patients, the compliance of the bladder decreases, high-amplitude detrusor hyperactivity is diagnosed, which leads to retrograde hydraulic pressure and damage to the VMP. Critical values are greater than 40 cm of water. Art. For this group of patients, the measurement of detrusor leakage pressure is appropriate in the context of a video-dynamic study.

Abdominal leakage pressure is used mainly for the diagnosis of stress urinary incontinence in women:

• type III is characterized by a pressure below 80 cm of water. (due to insufficiency of the internal sphincter);
• for type II - above 80 cm of water. (due to hypermobility of the urethra).

The standard equipment, any of the catheter types (water, air filled, "microtype") of the smallest possible size for measuring intravesical pressure and a standard rectal catheter are used for the study. When interpreting the data, the correct calculation of parameters is important, taking into account the patient's position, starting pressure and possible artifacts.

Intraurethral pressure profile

It is a measurement and graphical representation of the intralumin pressure over the entire length of the urethra. There are two main methods of measurement: static and dynamic. For static measurement, the theoretical basis is the proposition that. That the pressure of the flow of urine should be the force that is needed to open the urethra and begin urination. Thus, the pressure / resistance is measured at each point along the entire length of the urethra. With static passive profilometry, the patient is at rest. With stress profilometry, the patient is offered to periodically cough and strain, during which time the urethral resistance is measured.

Dynamic measurement of intraurethral pressure profile is carried out at the time of urination. Measured parameters:

• urethral closure pressure - difference in urethral and vesicle pressures;
• urethral closure pressure (stress) - difference in urethral and cystic pressure when coughing;
• maximum urethral pressure - maximum recorded pressure in the measurement zone;
• the maximum closure pressure of the urethra is the pressure at the point where the urethral pressure most exceeds the bubble pressure;
• maximum closure pressure of the urethra (stress) pressure at the point where the urethral pressure is most superior to the bladder pressure when coughing;
• the urethral closure pressure profile the difference in urethral and cystic pressure at all points along the length of the urethra during coughing. Positive peaks correspond to the areas of urine retention (the pressure in the urethra is higher than that of the vesicle), and the negative peaks correspond to the incontinence zones (bubble pressure is higher than the urethral one);
• the functional length of the profile the length of the urethra where the urethral pressure is above the vesicle;
• pressure transmission - is determined by the ratio of increase in intravesical pressure increase to the increase in urethral pressure during cough, expressed in percent. Normally, the ratio is 1: 1 (100%). With hypermobility of the urethra, when its proximal part loses its normal intraabdominal position and is outside the transmission zone, the indicator decreases.

Investigation of intraurethral pressure profile is performed on standard equipment using a three-way catheter with infusion channels, measuring intravesical and urethral pressures. A "micro-type" catheter is preferred. To move the catheter through the urethra at a constant speed and fix it at the outer opening, use a special device - a puller.

The study of the profile of intraurethral pressure is included in the standard of examination of women suffering from urinary incontinence. Less common for men (mainly with decompensation of the external sphincter and postoperative urinary incontinence).

The study of the profile of intraurethral pressure to determine urodynamics has no unequivocal opinion. Different specialists give preference to one or another method of measuring it, and some even refuse to do it. Nevertheless, in a number of clinical situations, this research is necessary and allows us to evaluate the urodynamic situation collectively, and therefore. More precisely.