firstly, air pressure ballistic trajectory is more likely to cause ureter injuries, for air pressure ballistic trajectory is to break calculi with the mechanical energy. We have such experiences in life: if you hit balloons with one palm (the strength of palm’s mechanical movements), you can't break the balloon, for it can flop in the air. But if the ballon faces the desk or wall surface, you can break it. Similarly, to break the calculi through the mechanical energy, one must let the calculi be fixed to substances like desk or wall surfaces, which are the patient’s ureter wall, velum and kidney calix wall, and because the ureter wall is relatively thin and the kidney calix wall is thicker, the ureter injury is more frequent, usually 3-4% rate in it. To break calculi with holmium laser is different, whose theory is that water in calculi absorbs holmium laser and expands quickly, to make the calculi broken. Because calculi breaking would cost some energy, adding that strength of water’s expansion is emanated all directions around, force on the ureter wall is much smaller than that of air pressure ballistic trajectory, and neglectable. It is also proved to be this by facts.

Air pressure ballistic trajectory cannot break calculus packaged in polypi, while holmium laser can cut open the polypi firstly and then break the calculus. Holmium laser can treat parenchyma diseases like ureter straitness and small tumors, etc.

The success rate in breaking calculus through air pressure ballistic trajectory is 85%, while that of holmium laser is 98% or 100%. The success rate in breaking calculus through air pressure ballistic trajectory is so low , is mainly due the above theories of breaking calculus through air pressure ballistic trajectory, adding that sometimes the strength of air pressure ballistic trajectory is parallel to the ureter and can’t find proper vellums, too, or the calculus is relatively hard and small, etc.