A 19-year-old helmeted motorcyclist is brought to the emergency department by ambulance after a crash at approximately 55 miles per hour. He is combative, pale, and diaphoretic. An endotracheal tube is placed, and his blood pressure is 85/40 mm Hg while receiving crystalloid resuscitation. A focused assessment with sonography for trauma (FAST) examination of the abdomen demonstrates fluid in Morison’s pouch.
Abdominal hemorrhage can be intraperitoneal or extraperitoneal (e.g., retroperitoneal or within the abdominal wall), and secondary to either a primary or secondary process (e.g., after trauma).
Intraperitoneal hemorrhage can be life threatening and can arise secondary to trauma, spontaneously, or as a complication of anticoagulant medication, infection, or malignancy. Most intraperitoneal bleeding is related to traumatic solid organ injury. Splenic injury constitutes up to 49% of visceral injury after blunt trauma.1 Liver injury can be present in up to 10% of blunt abdominal traumas, but occurs in isolation much less commonly than the spleen.2
Extraperitoneal hemorrhage can occur between leaves of the mesentery, in the retroperitoneum, or in the abdominal wall. Retroperitoneal hemorrhage arises after trauma, ruptured aortic aneurysm, malignancy, pancreatitis, or as a complication of anticoagulant medication or endovascular procedures (e.g., coronary catheterization). Abdominal wall and muscular hematomas can likewise be a complication of anticoagulation or trauma, but also can be seen after forceful coughing or during pregnancy.3
Sudden deceleration injury or transmission of blunt force directly to the spleen or liver is responsible for most cases of intraperitoneal hemorrhage after trauma. Deceleration forces can cause capsular disruption and avulsion of ligamentous attachments, causing linear and stellate fractures of varying depths. Associated lesions are common and include ipsilateral rib fractures, hemothorax or pneumothorax, lung lacerations, and renal or adrenal injuries.
Abdominal wall and retroperitoneal hemorrhage can be related to intramuscular injections, or to anticoagulant medications, with or without antecedent trauma. Retroperitoneal hemorrhage can also be associated with major vascular injuries or malignancy and can be spontaneous.
Splenic injury presents with abdominal pain, with referred pain to the left shoulder (Kehr sign), while the pain after a liver injury can radiate to the right shoulder. Diffuse hemorrhage can lead to abdominal distention and shock with associated ileus. Intraperitoneal blood is a minor peritoneal irritant and so may be missed on physical examination. The diagnosis becomes more difficult in the presence of multiple injuries and can be complicated by closed head injury, drugs, or spinal cord injury.
Retroperitoneal hematomas present with generalized or localized pain. The larger the lesion, the more likely the pain is to be generalized.3 Physical examination tends to be nonspecific, but Cullen’s (peri-umbilical) or Grey-Turner’s (flank) ecchymosis has been described. Flank pain and pain radiating to the thighs are common.
Rectus sheath hematomas most often present with acute localized pain that is unilateral. Occasionally, ecchymosis over the site of the lesion can be seen. Classically, abdominal pain will be unchanged or increase with tensing of the abdominal wall muscles (Carnett’s sign). Depending on the amount of bleeding, other signs of hypovolemia may be present (e.g., tachycardia, hypotension).
The differential diagnosis of intra-abdominal fluid is broad (Table 26–1).
WORKUP AND CHOICE OF IMAGING
In the acute workup of trauma, ultrasound (US) has a definitive role in the evaluation of fluid in the peritoneum. The focused assessment with sonography for trauma (FAST) protocol is very well described in the trauma literature4 and is indicated in most trauma patients. Standard views of the pouch of Morison, the perisplenic space, and the pelvis can be performed in a few minutes. In addition, the examination is repeatable and can be performed without leaving the resuscitation area. US cannot, however, reveal the density of the fluid or evaluate the retroperitoneum. In addition, the examination is operator dependent and can be limited by patient habitus.
Computed tomography (CT) remains the gold standard for evaluation of the abdomen in the stable blunt-trauma patient and in patients with suspected retroperitoneal or rectus sheath hematoma. CT can detail the presence and amount of fluid in the abdomen, reveal its quality and source, and give detailed information regarding the state of intra-abdominal solid and visceral organs. Additionally, CT is the only reliable acute imaging modality that is capable of evaluating the retroperitoneum and abdominal wall.
Plain film has no role in abdominal hemorrhage. Magnetic resonance imaging (MRI) can provide good detail and can be useful in differentiating between an abdominal wall mass and a hematoma, but the prolonged time required for image acquisition render it impractical in an acute setting.
Peritoneal blood tends to collect near the source of bleeding initially, and then spills into dependent portions of the peritoneal cavity. Ultrasound evaluation of these dependent recesses, listed in Table 26–2, can reveal the presence of hemoperitoneum.
|Morison’s pouch||Hepatorenal recess||Most dependent recess of upper abdomen and most common site of blood collection seen on CT scan|
|Perihepatic space||Right subphrenic|
|Perisplenic space||Left subphrenic|
|Paracolic gutters||Lateral to ascending and descending colon||Blood frequently tracks down root of mesentery to right paracolic gutter|
|Pelvis||Adjacent to urinary bladder|
FAST examination of the abdomen typically includes three intra-abdominal views: (1) Morison’s pouch, (2) the perisplenic space, and (3) the pelvis, as well as a transverse subxiphoid cardiac view. Blood and fluid appear as a black space between two organs (Figures 26–1, 26–2, and 26–3).
The appearance of blood in the peritoneal cavity by CT depends on the site of bleeding, duration of extravasation, and whether it is clotted or lysed. Immediately after hemorrhage, blood has the same attenuation as intravascular blood. Free blood (Figure 26–4) has Hounsfield units (HU) of 30 to 45, whereas clotted blood (Figure 26–5) has HU of 50 to 100, depending on density of clot.5 Clotted blood in the peritoneal cavity will begin to lyse rapidly, and attenuation will decrease within several days. Failure of this change to occur may indicate ongoing hemorrhage. Active arterial hemorrhage is indicated by focal or diffuse high-attenuation of areas of extravasated blood (HU 80–370) and can even be isodense with the abdominal aorta (Figures 26–6 and 26–7).