Anirudh Kohli Blunt abdominal trauma resulting from sudden deceleration or direct impact remains one of the commoner causes of death and disability in young/middle-aged adults. Severe head or thoracic aortic injuries may lead to death at the site of accident, but victims of blunt abdominal trauma often survive long enough to receive emergency treatment. Over the last decade or so, Sonography has replaced diagnostic peritoneal lavage as the initial examination in detection of free intraperitoneal fluid. This is, as sonography is quick, non-invasive, readily available and has a high level of accuracy. Unfortunately, the information provided by Sonography as regards visceral injuries is less consistent and often inadequate. CT is now widely used to examine the acute trauma victim, as it enables a comprehensive imaging of multiple body regions and organ systems in a single examination. It is also not limited by obesity, bowel gas or operator dependence; factors which impede the quality of sonography. Theoretically, MRI may have certain advantages over CT, as it does not use ionizing radiation and iodinated contrast medium. Not only is the information available on CT superior to MRI, MRI is impractical in acute trauma patients. It is difficult to monitor patients in an MRI unit without MR compatible equipment. Further MRI takes much longer up to 30 minutes, compared to MDCT, which can scan chest, abdomen, pelvis in less than a minute. The radiation dose in present-day spiral scanners is very low, nonionic contrast agents are also extremely safe. Free intraperitoneal fluid is a common finding on CT scans of patients with blunt abdominal trauma. The attenuation values of acutely extravasated blood can vary considerably, from those of intravascular blood to ascites or bile. However, usually, the HU values of extraperitoneal blood is usually high in the range of 30–45 HU due to concentration of haemoglobin and its products, layering and clot formation. The HU values of a clot may measure 50–60 HU or even more. With time and clot retraction, the HU values of extravasated blood drops slowly to resemble the values of ascitic fluid. Initially, small amounts of intraperitoneal fluid accumulate in the compartment at the site of bleeding. Subsequently, with an increase in the amount of intraperitoneal blood, the blood tracks like any free intraperitoneal fluid through the communicating peritoneal spaces, such as from Morrison’s pouch via the paracolic gutter to the pouch of Douglas. The presence of a small clot localized in a peritoneal compartment is an important indicator that the site of injury would be in an adjacent organ or structure even if the injury is not visualized on the CT scan. The degrees of haemoperitoneum may be crudely estimated depending on the number of compartments involved (Morison’s pouch, perisplenic, perihepatic, paracolic gutters and pouch of Douglas). Fluid in one compartment would indicate approximately 100–200 mL, in two compartments 250–500 mL (moderate hemoperitoneum), more than two compartments (major haemoperitoneum) 500 mL. It is important to note that most patients with blunt abdominal trauma have a small amount of free intraperitoneal fluid, which is often of no significant clinical importance. However, the presence of a small amount of free fluid between mesenteric loops should raise the suspicion of an injury of mesentery or bowel. Active bleeding may be visualized as extravasation of intravenously injected contrast material. The liver is the most common injured organ in the abdomen. The management of hepatic trauma has dramatically changed with the use of multidetector CT. Nonsurgical management has now become the preferred strategy in hemodynamically stable patients with blunt liver trauma. However, patients who are hemodynamically unstable despite fluid resuscitation and who have peritonitis, a finding that is suggestive of additional hollow viscus injury, should undergo emergency laparotomy. CT can accurately delineate the pathologic anatomy, help determine the severity of injuries and quantify the degree of hemoperitoneum, as well as reveal associated injuries to other abdominal organs, retroperitoneal structures, and the gastrointestinal tract. CT can also be used to assess complications of liver trauma and document the healing process in liver injuries while the patient is managed conservatively. The posterior segment of the right lobe of the liver is the most commonly affected hepatic segment in view of the close proximity to the spine and ribs and fixity to the coronal ligaments (Fig. 9.23.1). Injuries to the left lobe are more commonly vertical in orientation due to anterior compression of the left lobe against the spine. In these injuries, there may be associated injury to the pancreas, duodenum, small bowel and transverse colon. Traumatic lesions of the liver are classified as: Contusions are rare – these are essentially areas of oedema and microscopic bleeding without evidence of frank disruption of the liver parenchyma or associated hematoma. On CT they appear as ill-defined areas of decreased attenuation. These lesions heal without complications. Lacerations are the most common type of hepatic injury. These appear as linear low attenuation lesions which may be isolated or clustered in branching or parallel configurations usually paralleling the intrahepatic vasculature. It is important to localize these lesions either in a superficial, deep or perihilar location. Superficial lacerations are less than 3 cm wide, deep are more than 3 cm wide. The deep and perihilar lacerations are important as they often have a higher incidence of complications, such as bile duct injuries, hemobilia and biliomas. Lacerations, which extend towards the hepatic vein confluence or intrahepatic IVC may be associated with hepatic vein or IVC laceration. Lacerations or haematomas involving the bare area of the liver tend to be associated with extraperitoneal/retroperitoneal haemorrhage rather than intraperitoneal haemorrhage and are often associated with injuries to retroperitoneal organs. Lacerations which extend through the hepatic capsule are usually associated with hemoperitoneum. Intraperitoneal bleeding following liver injuries is usually marked due to the dual blood supply. Hematomas may be subcapsular or in an intraparenchymal location. Subcapsular haematomas are usually more common following penetrating liver injuries. Subcapsular hematomas are typically lenticular in shape with a sharp margin with the liver parenchyma. Intraparenchymal hematomas are round or oval. A haematoma or bilioma may get infected requiring percutaneous catheter drainage. Intraparenchymal appear as ill-defined hyperdense lesions on plain study and hypotenuse lesions after contrast as the liver enhances and the haematome does not. Hepatic fracture represents a laceration that extends through the entire width of the liver with resultant fragmentation and interruption of the vascular blood supply. Fractures approaching the course of the central hepatic veins of the inferior venacava are of particular importance to the surgeon performing exploratory laparotomy since major haemorrhage may occur when mobilizing the liver. Disruption of the portal triad can result in pseudoaneurysms or arterio-portal fistulas. CT angiography is an excellent means to demonstrate these fistulas, though most would need further evaluation with DSA and subsegmental transcatheter embolization. There may be an active arterial or venous injury this is seen as active extravasation of intravenously administered contrast and would warrant a DSA. Pseudoaneurysms – these are a rare complication which occur due to disruption of arterial wall with an associated haematoma and formation of a fibrous capsule. It is seen as a well-defined rounded hyperdense area which enhances markedly in the arterial phase after administration of contrast. These may be detected incidentally and patients may be asymptomatic but they should be treated urgently with embolization as they can rupture leading to catastrophic consequences. They may rupture into the liver parenchyma, biliary tree, duodenum or peritoneum. Hepatic lacerations and haematomas demonstrate a decrease in attenuation with time and usually resolve in 6–8 weeks. Occasionally initially there may be a slight increase in size on follow up studies due to osmotic absorption of fluid (Fig. 9.23.2).
9.23: Abdominal trauma
Introduction
Intraabdominal haemorrhage
Liver
Vascular complications
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