Abdomen Injury Mechanisms

The abdomen consists of the intestine and bladder plus female uterus, which is protected by the strong muscles and skin of the abdominal wall at the front and sides and spine at the rear.  As the both the upper and lower intestines are ‘hollow’ organs (partially air filled) they are relatively free to move within the abdominal cavity resulting in many different mechanisms of injury.  The majority of blunt object impact injuries are either perforations or contusions of the intestines or rupturing of associated blood vessels.  Localised impacts to the isolated small intestine can cause localised severe injury plus the fact that the effects of blunt injury can be delayed and very serious (acute intestinal obstruction by haematoma) making identification of injury mechanisms difficult.  In terms of severity it is also difficult to evaluate, as intestine injuries are normally associated with other pelvis or thorax injuries, for example parts of fractured pelvis perforating the colon.

The urinary bladder is well protected by the pelvis so the only blunt object impact injury occurs at the top and most of these are ‘burst’ ruptures produced by high internal pressures exceeding the bladder wall strength.

The ungravid uterus (not pregnant) is very rarely injured because of its location in the pelvis however the gravid uterus (pregnant) because of its increased size has a much greater potential for injury many causing foetal death.  In automotive accidents these have been associated with the wearing of lap belts, either by direct loading from a misplaced lap belt, above the pelvic iliac wings, or compression of the uterus with the hyper flexion of the torso when a shoulder belt is not used.

Penetration injuries into the abdominal cavity can occur from both foreign objects, in the rail vehicle these would be sharp edges produced from fractured and deformed fixtures, and from fractured ribs.  Any puncturing of the abdominal wall is serious due to the risk of external infections.

In terms of injury level they range from minor lacerations and contusions, AIS 2, to massive perforation, rupture and abdominal cavity contamination, AIS 4 – 5.