Despite the number of the pellets  the bulky back muscles  prevented any of them to invade through the chest wall ,

no evidence of  hemo or pneumothorax .

The mechanism of injury may be categorized as low, medium, or high velocity. Low-velocity injuries include impalement (eg, knife wounds), which disrupts only the structures penetrated. Medium-velocity injuries include bullet wounds from most types of handguns and air-powered pellet guns and are characterized by much less primary tissue destruction than wounds caused by high-velocity forces. High-velocity injuries include bullet wounds caused by rifles and wounds resulting from military weapons.

Shotgun injuries, despite being caused by medium-velocity projectiles, are sometimes included within management discussions for high-velocity projectile injuries. This inclusion is reasonable because of the kinetic energy transmitted to the surrounding tissue and subsequent cavitation, as described by the following equation in which KE is kinetic energy, M is mass, and V is velocity:

KE = ½ MV2

The amount of tissue damage is directly related to the amount of energy exchange between the penetrating object and the body part. The density of the tissue involved and the frontal area of the penetrating object are the important factors determining the rate of energy loss.

 injuries is listed as follows