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    Home > Active Ingredient News > Urinary System > Clinical essentials | Shock wave lithotripsy of upper ureteral calculi

    Clinical essentials | Shock wave lithotripsy of upper ureteral calculi

    • Last Update: 2021-04-27
    • Source: Internet
    • Author: User
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    In August 1980, the Germans used the Dornier HM3 shock wave lithotripter for the first time to treat upper ureteral calculi, and the success rate was only about 60%.

    It was not until the mid-1980s that upper ureteral calculi formally became an indication for SWL (extracorporeal shock wave lithotripsy).

    According to reports at the time, the success rate of SWL is generally higher than 80%, and often even exceeds 90%.

    In 1990, SWL officially became the preferred treatment for upper ureteral stones.

    The upper ureteral calculi are close to the kidney, and the average volume is larger than the middle and lower calculi, which poses a greater threat to kidney function.

    If the stone stays locally for more than 6 weeks, the self-expulsion rate is very low.

    Therefore, in the era of minimally invasive therapy, it is generally advocated to take surgical intervention as early as possible for upper ureteral stones.

    1.
    Preoperative preparation points The upper part of the ureter is adjacent to the colon, duodenum and other abdominal organs.
    In the case of more intestinal contents, it is necessary to fast or clean the intestines, which will help to clearly display the stones and reduce the attenuation of shock waves.

    2.
    Shock wave approach With the improvement of the flexibility of the shock wave lithotripter positioning system, the shock wave source can move up and down, and a comfortable supine position can solve most of the upper stone positioning.

    The lumbar and lateral lumbar approach can reduce the influence of intestinal gas on the lithotripsy effect; the abdominal approach has a smaller treatment depth, which is especially suitable for obese patients with upper distal stones.

    3.
    Treatment parameters There is a lack of a water environment conducive to crushing of ureteral stones.
    Compared with kidney stones of the same size, a larger therapeutic dose is required.

    In the early days, when the Dornier HM3 shock wave lithotripter was used to treat upper ureteral stones, the upper limit of energy used was up to 30kV, with 3000 shocks; now it is changed to the upper limit of energy of 24kV, with 2400 shocks, but the efficiency of lithotripsy has not been significantly reduced.

    Later, Parr found in experiments that there is energy saturation when crushing artificial ureteral stones.
    Even if the energy of the shock wave is increased, it may not significantly improve the crushing effect of the stones.

    Therefore, excessive energy input is unnecessary and even harmful.

    The number of impacts of ureteral stones depends on the response of the stones to treatment.
    Small stones may be completely crushed within 1000 times.

    Large stones can often be scattered and elongated along the lumen after disintegration.
    Larger fragments in different parts can be tracked and strive to be completely crushed; when the rated impact dose is reached, the stone has not been completely crushed.
    The impact should be suspended and wait for the next treatment .

    Excessive shock can only increase the local congestion and edema of the ureter, and further reduce the local space, which is not conducive to gravel and stone removal.

    It is generally believed in foreign countries that when SWL is used to treat large-volume incarcerated ureteral stones, the shock wave focus should be placed on the upper edge (proximal end) of the stone, and the favorable conditions of the "water-stone" interface should be used to give full play to the lithotripsy Effectiveness (Figure 1).

    Figure 1 The target setting of shock wave focus when SWL is used to treat incarcerated ureteral stones abroad, but the author holds a different view: the upper ureter swings up and down due to the influence of respiration.
    The moving distance is 5-20mm, with an average of 11mm.
    The treatment target cannot be fixed during the SWL process.
    If the upper edge of the stone is used as the impact target, as the stone position moves down during inhalation, the shock wave "hit" phenomenon will occur, and the overall hit rate of the stone will decrease instead.
    (figure 2).

    Moreover, the domestic shock wave lithotripter has a larger focus, and it is unnecessary to use the upper edge of the stone to locate it.

    Therefore, the author believes that the treatment of any type of upper ureteral stones should focus on the geometric center of the stone.

    Figure 2 The effect of breathing action on different positioning positions of the stone A.
    Foreign shock wave lithotripter (the focal spot is consistent with the geometric center of the stone); B.
    Foreign shock wave lithotripter (the focal spot is placed on the upper edge of the stone); C.
    Domestic shock wave Lithotripter (the focal spot is consistent with the geometric center of the stone); D.
    Domestic shock wave lithotripter (the focal spot is placed on the upper edge of the stone) 4.
    Postoperative follow-up After in-situ shock wave lithotripsy, the fragments of the stone are generally 1~ The stone discharge starts in 3 days, and the average clear time is about 4.
    6 days. However, some stones may be embedded in the lumen of the ureter even if they are fragmented, so that the stones cannot be discharged by themselves in a short period of time.
    The reason is that the local shock waves cause edema of the ureteral mucosa and hinder the discharge of stones.

    After the edema disappears, as the inner diameter of the lumen expands, the stone fragments will pass by themselves and be gradually discharged.

    If there is no significant change in the shape of the stones on the KUB two weeks after the operation, a second-stage lithotripsy should be used.

    If the effect of re-shock is still not good and the basic shape of the stone remains unchanged, internal lithotripsy should be used instead of repeated shocks, so as not to aggravate local tissue damage and delay the timely treatment of urinary tract obstruction.

    The content of this article is excerpted from "The Principle and Application of Shock Wave Lithotripsy" (China Science and Technology Press).

    Yimaitong has been authorized by the publishing house.

    For more information, please read the original book.

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