Urodynamic examination technique of upper urinary tract

The examination methods include renal or ureteral fistula manometry, percutaneous renal pelvis puncture perfusion manometry, bladder and ureter intubation manometry, intraoperative renal pelvis and ureter puncture manometry, and dynamic radiological observation during intravenous urography. There are two points of great clinical value: the measurement of urine discharged from urethral orifice per unit time is called urine flow rate measurement, and its unit is ml/s, which can reflect the general level of urine storage and urination function of lower urinary tract and is the basic item of urodynamic examination of lower urinary tract. It is often used to screen dysuria, and can also provide objective indicators for evaluating curative effect.

The important parameters of this examination are: maximum urine flow rate (MFR), average urine flow rate (AFR), urination time, urine flow time, urine volume, etc. Among them, MFR is the most significant. However, MFR can be affected by the patient's age, gender, body position, psychological factors, urine volume and other factors, so it should be noted that when the urine volume is 500ml, MFR has a downward trend. In men, MFR tends to decrease with age, and the normal value of MFR decreases obviously after 50 years old. Generally speaking, when the urine volume is ≥200ml, the normal male MFR is ≥ 20 ~ 25ml/s and the female MFR is ≥ 25 ~ 30ml/s. MFR ≤15ml/s should be suspected as abnormal urination, while MFR≤ 10ml/s is obviously abnormal. The patient may have lower urinary tract obstruction (prostatic hypertrophy, etc.). ) or neurogenic bladder.

Urinary flow rate curve is a curve that can reflect the change of instantaneous urinary flow rate when measuring urinary flow rate. The shape of normal urine flow rate curve is mostly related to age and urine volume, while abnormal curve is often related to the nature of disease, which can be used as a reference for diagnosis. This examination mainly reflects the function of bladder by measuring the relationship between pressure and volume in bladder. The process of bladder filling (urine storage function) and contraction (urination function) can be recorded as bladder pressure-volume curve (CMG). From the curve, we can know: the volume and compliance of bladder; Stability of bladder; Sensory and motor innervation of bladder. This examination is mainly used for the diagnosis and classification of patients with neurogenic bladder.

During the examination, the catheter must be inserted into the bladder through urethra, and the bladder filling medium (normal saline or CO gas) should be gradually filled into the bladder. In this process, we should pay attention to the patient's feeling and reaction to bladder filling, the change of bladder internal pressure (i.e. bladder compliance) when bladder volume increases, and whether there is inhibitory contraction (i.e. involuntary contraction of bladder, which is manifested as the pressure peak of 15cmHO on CMG). Sometimes, in order to stimulate the hidden and uncontrolled contraction, it is necessary to repeat the examination under the conditions of accelerating the filling speed, changing the body position and coughing. The maximum bladder filling volume (not the actual bladder capacity) is when the patient has a strong sense of urination. Stop filling at this time, instruct the patient to urinate, and observe whether the detrusor can consciously contract. Then, ask the patient to restrain urination and observe whether he can relax the detrusor actively. Sometimes, in order to make a differential diagnosis, some drugs (such as propafenone and carbamoyl methylcholine hydrochloride) can be given to repeat this examination.

This examination requires a bladder pressure and volume meter. In the past, the water column manometer was widely used, which needed intermittent inflation pressure measurement, and the corresponding CMG was hand-painted, so the inspection result was inaccurate. Modern bladder pressure volumeter adopts various pressure sensors and recorders, which can continuously and automatically record corresponding curves and improve the accuracy of examination.

Its main disadvantage is that the measured intravesical pressure during bladder contraction is the sum of intra-abdominal pressure and detrusor systolic pressure, and it is impossible to distinguish whether the increase of intravesical pressure is caused by detrusor contraction or the influence of intra-abdominal pressure. At present, the value of this examination is mainly manifested in the filling period, which is called bladder pressure and volume measurement during filling period. This is a basic combined examination technique for urodynamic examination of lower urinary tract, which can accurately judge the contractility of detrusor and lower urinary tract obstruction, thus making up for the shortcomings of the above two examinations when they are used alone. This examination requires simultaneous measurement of bladder pressure, intra-abdominal pressure (rectal pressure), detrusor systolic pressure (bladder pressure minus intra-abdominal pressure) and urine flow rate during urination. During the examination, manometric catheters should be placed in the bladder (transurethral or pubic puncture) and rectum and connected with their respective pressure sensors. When the patient urinates to measure the urine flow rate, the recorder can record four corresponding curves at the same time. Among them, the detrusor pressure curve is drawn by the electronic circuit in the instrument.

From the recorded four curves, we can not only know the parameters such as bladder neck opening time, maximum urination pressure, detrusor systolic pressure and urine flow rate, but also diagnose some diseases (such as detrusor sphincter dyssynergia) through the corresponding time correlation between pressure and urine flow rate curves. According to the results of this examination, the intravesical pressure can be calculated according to the formula [9 18-02]/[918-0/] (where [918-02] is the intravesical pressure). This value is about 0.6 for men and 0.2 for women. An increase in this value indicates lower urinary tract obstruction. When urinating, the pressure in the bladder is mostly 45 ~ 80 cmho.

Generally not more than 100cmHO. At the maximum urine flow rate, the intravesical pressure in men is about 70 ~ 80 cmho, and that in women is about 55 ~ 65 cmho.

According to the measurement results of pressure/urine flow rate, the following conditions can be found, as shown in the following table [Significance of pressure/urine flow rate measurement]. The continuous measurement and recording of urethral pressure is called UPP. This examination is mainly used to understand urethral function. There are two types of UPP, namely, static measurement under non-micturition state and dynamic measurement under micturition state. The former mainly reflects the ability of urethra to control urination in closed state, while the latter reflects the ability of urethral pressure to change accordingly when urination occurs.

The methods of UPP are: liquid or gas perfusion manometry; Balloon catheter manometry; There are three methods to measure the pressure of urinary catheter with miniature pressure sensor. Among them, liquid or gas perfusion manometry is widely used.

During the examination, the manometric catheter should be inserted into the bladder through the urethra, and then the catheter should be pulled out at a constant speed along the urethra with the help of mechanical devices. When using liquid or gas perfusion pressure measurement method, it is necessary to continuously inject liquid or gas into the pressure measurement catheter at a constant flow rate at the same time. The pressure of injected liquid (gas) that pushes open the closed urethral wall and enters the urethral cavity is close to the closing pressure there. Therefore, with the continuous pulling out of the manometric catheter, the pressure at various points in the urethra can be recorded, and the corresponding urethral pressure distribution curve can be drawn by the recorder.

The urethral pressure distribution curve can provide the following data: bladder pressure, maximum urethral pressure, maximum urethral closure pressure and functional urethral length. The maximum urethral pressure is about 85 ~ 126 cmho in men and 35 ~1/5 cmho in women (it decreases obviously with age). The functional length of male urethra is about 5.4±0.8cm, and that of female urethra is about 3.7±0.5cm. In addition, due to anatomical reasons, the shape of urethral pressure curve between male and female is obviously different. The former shows the peak pressure of prostate and urethra, while the latter shows a bell-shaped curve.

Repeated examination in different positions, coughing or urinating can often get more information, which is helpful to make a more accurate judgment of urethral function. Used to understand the function of external urethral sphincter. Because the external anal sphincter and external urethral sphincter are innervated by pudendal nerve, the EMG of external anal sphincter is generally used to reflect the activity of external urethral sphincter.

During examination, the electrode should be placed on the surface of sphincter (surface electrode) or penetrated into sphincter (needle electrode). Generally speaking, the former operation is simple and the patient's pain is small, while the latter operation is more complicated, but the result is more accurate.

Under normal circumstances, the external urethral sphincter maintains a certain tension and participates in controlling urination, so EMG can show continuous EMG activity, which can be enhanced when coughing hard to resist the increase of bladder pressure. When urinating, due to the relaxation of external urethral sphincter, EMG is static. Once the urine is finished, EMG activity resumes.

This kind of inspection is rarely carried out alone and is usually used in combination with some of the above-mentioned inspections. When the EMG activity continues to increase during urination, it is an important diagnostic basis for the dyssynergia of the external sphincter of detrusor. The above tests focus on reflecting the function of a certain aspect of the lower urinary tract. Therefore, in order to fully understand the function of lower urinary tract, it is necessary to selectively combine these examination techniques according to the specific conditions of patients. At present, more advanced urodynamic examination instruments are often combined. In addition to the above inspection, several or all items can be selected for joint inspection at the same time as needed. Inspection data will be recorded by recording paper, TV video and film photography. For subsequent retrieval. Some newly introduced inspection instruments also have computer equipment, which can analyze and process some curves and images to make the inspection results more accurate.

The commonly used synchronous combined examination techniques in clinic are: urine flow rate/pressure/electromyography; Bladder pressure volume/electromyography; Urethral pressure distribution/pressure/electromyography, etc. Other complicated synchronous combined examinations often add synchronous cystourethrography when urinating, and record all the examination results through TV video and film photography.

The emergence of urodynamic examination technology is an important progress in urology, but urodynamic examination itself is interfering with the normal physiological activities of urinary tract and affecting the spirit and psychology of patients, so the examination results may not reflect the actual situation of patients, so detailed medical history, comprehensive physical examination and necessary other examinations must not be ignored.