PEDESTRIANS, motorcyclists and pedal cyclists, termed vulnerable road users, continually account for the majority of road users killed yearly. Passenger car occupants are the second largest casualty group. Most of them do not wear a seat belt, although it is compulsory.

Traumatic injury can be blunt or penetrating. Motor vehicle accidents are capable of producing either. Virtually any area of the body may be injured, but for the purposes of this discussion, we will focus on blunt abdominal trauma and the role played by the emergency radiologist in the management of these patients.

The morbidity (illness), mortality (death) and economic cost resulting from trauma in general, and blunt abdominal trauma in particular, are substantial. Trauma is the leading cause of death for men and women under the age of 45 years.

In the United States, trauma accounts for more than one-third of all emergency department visits and results in more than 80 billion per year in direct medical care costs.

Where available and/or affordable in Jamaica, and certainly in all level one trauma centres in developed countries, the “panscan” (computerised tomography [CT] of the head, neck, chest, abdomen and pelvis) has become an essential part of the early evaluation and decision-making algorithm for stable patients who sustained abdominal trauma.

Management of trauma patients is therefore heavily reliant on the emergency radiologist who interprets the findings of CT examinations and other radiological investigations and effectively identifies patients who must be managed surgically and those who may be managed conservatively. Conservative non-surgical therapy is preferred for all but the most severe injuries affecting the solid organs.

The most common causes of blunt abdominal trauma are motor vehicle collisions, falls from heights, assaults, and sport accidents.

Three basic mechanisms explain damage to the abdominal organs: deceleration, external compression and crushing injury.

In order of frequency, the most commonly injured organs and structures are the spleen, liver, kidneys, small bowel and/or mesentery, bladder, colon and/or rectum, diaphragm, pancreas, and major vessels.

Care of the trauma patient involves a multidisciplinary approach. The radiologist is an integral part of the primary assessment team.

The primary goal is the detection of potentially lethal but treatable injuries, so that immediate intervention can be undertaken to maintain circulating blood volume to perfuse vital organs and allow adequate gas exchange and oxygenation of blood.

The investigations may include anything from a chest X-ray, to an ultrasound, to a CT depending on the severity of the trauma and the stability of the patient.

FAST (focused assessment with sonography for trauma) studies are focused ultrasounds used to detect fluid (blood) within the abdomen. They usually precede the decision to undergo surgery. Modern trauma hospitals are designed with CT machines within or near to the Accident and Emergency bay and much information about the degree of injury can be quickly obtained without delaying surgery, if necessary.

HEMOPERITONEUM AND FREE PERITONEAL FLUID

Injury to solid organs and bowel is commonly associated with bleeding. Analysis of the amount and density of the blood gives important clues as to the location and severity of injury.

Blood located adjacent to the source of haemorrhage tends to be partially clotted and will appear denser on CT. This is termed the sentinel clot sign.

A large amount of intra-abdominal blood may not necessarily mean surgery. The rate of bleeding and the presence of active bleeding are often more important predictors of the likelihood of surgery. In male patients with isolated free fluid, but no other suspicious findings, close observation before surgery is the current recommendation.

SPLENIC INJURY

The spleen is important for proper functioning of the immune system. The risk of overwhelming infection increases dramatically if it is removed.

The spleen is the most commonly injured organ in blunt trauma. Surgical removal of the spleen after trauma is only done as a last resort.

Radiologists use a CT-based splenic injury scale system developed by the American Association for the Surgery of Trauma (AAST). The scale grades injury based on the size and location of splenic lacerations and clots.

AAST grade three or higher injuries are treated surgically. The splenic laceration should therefore be greater than three centimetres or involve splenic vessels and the hematoma should cover >50 per cent of the splenic surface area or be greater than five centimetres and expanding.

Other factors such as the amount of intra-abdominal blood and the presence of active bleeding are also important.

HEPATIC INJURY

Similar to splenic injury, every effort is made to treat hepatic injuries conservatively. The AAST liver injury scale also considers size and location of hematomas and liver lacerations.

Other considerations include:

(a) extension of the injury to the hepatic veins, which usually requires surgery to control active bleeding;

(b) the presence of active bleeding into the abdominal cavity, which can be treated with endovascular intervention; and

(c) the presence of a large amount of blood within the abdomen.

CT is also able to look for complications of conservative treatment such as delayed bleeding or bile leaks.

BOWEL AND MESENTERIC INJURIES

These are rare injuries, however, prompt identification of bowel injuries is extremely important because delay of just eight to 12 hours increases the risk of illness or death from infection.

Specific bowel injury signs include disruption of the bowel wall, spillage of oral contrast given by mouth and free air within the abdomen.

The mesentery is composed of membranous tissue, which anchors the bowel to the posterior abdominal wall. Blood vessels run in-between these folds of tissue. Specific signs of mesenteric injury include blood clots within the mesentery, spillage of contrast given in the veins, disruption or irregularity of the mesenteric vessel walls.

Similar grading systems can be applied to the kidneys and pancreas. CT is also useful for evaluation of bladder, diaphragmatic and vascular injuries. The radiologist provides a method of assessing the degree of intra-abdominal injury, which is superior to clinical examination, in this situation, and in so doing gives the body a chance to heal itself.

Dr Duane Chambers is a consultant radiologist and founding partner of Imaging and Intervention Associates located at shops 58 and 59 Kingston Mall, 8 Ocean Boulevard. He may be contacted through the office numbers 618-4346 or 967-7748.