Clinical Essentials | Shock Wave Lithotripsy for Middle Ureteral Stones

The middle ureteral calculi overlap with the iliac bone.
In the early stage, due to the stone positioning and impact technology, it was inconvenient to use the HM3 sink type first-generation shock wave lithotripter to treat the middle ureteral calculi.
Later, with the second-generation shock wave lithotripsy With the advent of the camera, especially the introduction of high-definition and digital subtraction X-ray technology, the positioning and posture problems of SWL have been solved.

The procedure of SWL for ureteral stones is as follows.

1.
The main points of preoperative preparations The middle section of the ureter is the most superficial part of the entire ureter.
The stones are 2~6cm away from the abdominal skin and are greatly affected by intestinal gas.
Preoperative bowel preparation is more important.

In addition, the middle ureter is accompanied by abdominal blood vessels, and there is a lithotripsy center equipped with ultrasound diagnostic equipment.
The shape and diameter of the blood vessels should be routinely reviewed before the operation of the stone location.

2.
The ureteral calculus in the middle of the shock wave approach can only be taken through the abdominal approach, whether it is the upper or lower positioning lithotripter.

In the case of ureteral dilatation, ultrasound can guide the pulsating iliac vessels to find the dilated ureter and stones (Figure 1); if there is no ureteral dilatation, the second ureteral stenosis can be found in the superficial part of the iliac vessels, such as stone obstruction in the middle.
, The upper part of the stone can generally show the diameter of the ureter and the typical strong echo and acoustic shadow of the stone.

Most of the X-ray positioning lithotripters can only take the prone position.

Since the middle section is relatively shallow, the water bladder often needs to be highly filled to be well coupled.

When X-ray positioning, you should pay attention to refer to the location of the stones on the preoperative abdominal X-ray film, carefully observe and look for the target on the monitor.

It can make full use of the moment of breathing to distinguish dynamic stones from static bone background.

When the stone image is too light, double-dose intravenous urography or ureteral catheterization can also be used to assist in positioning.

According to Sun Xizhao's report, the accuracy of direct X-ray positioning of stones is 98%, and only 2% of those who rely on intravenous urography to assist in positioning.

Figure 1 Ultrasonic positioning treatment of middle ureteral calculi Figure 3.
Treatment parameters The middle ureteral distance is superficial, the shock wave energy attenuation is less, the volume of the middle ureteral calculi is also smaller than that of the upper ureteral calculi, and it is not affected by breathing.
In theory, treatment is needed The dose is relatively small.

Therefore, the shock wave lithotripsy effect of the stones in this part should be ideal.

Zhang Dongfang compared the treatment parameters of 464 cases of ureteral calculi (Table 1).
The results showed that as the ureteral calculi moved downward, the therapeutic dose gradually decreased, the stone-free rate and efficiency quotient increased, and the re-shock rate decreased (Table 2 ).

Table 1 Comparison of SWL treatment parameters of various parts of ureteral calculi (±s) Table 2 Relationship between ureteral calculi position and SWL curative effect n (%) Because the volume of middle ureteral calculi is small, and the middle ureter also has fewer stones, this section of ureteral calculi is embedded There are fewer chances to stop, and the swing amplitude of the middle ureter with respiration is much lower than that of the upper ureter.
The stone hit rate is higher, so the lithotripsy effect is satisfactory.

Cass compared 143 cases with Medstone STS lithotripter and 53 cases with Dornier HM3 lithotripsy machine in the middle ureteral calculi.
The results showed that the stone-free rate after treatment was 80% and 75%, and the retreatment rate was 14 % And 19%.

According to Sun Xizhao, the single-stage success rate of SWL for middle ureteral stones is 75%, second-stage 19%, and third-stage 6%.

The stone-free rate for 3 months was 96%.

Bagkey summarized and analyzed 340 literature reports on SWL treatment of upper and middle ureteral calculi in 10 years, compared the treatment effects of different models, and concluded that the success rate of SWL is related to the size, composition, and degree of incarceration of the stones.

Stones with a diameter of less than 10mm have better curative effects; stones with a diameter of 10mm or more have poor curative effects; single stones with more stones have good curative effects; compared with SWL for upper and middle ureteral stones, there is no significant difference in the total success rate of different models of lithotripsy (table 3).

Table 3 Summary of SWL curative effect of upper and middle ureteral calculi.
The content of this article is excerpted from "Principle and Application of Shock Wave Lithotripsy" (China Science and Technology Press).

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