INCIDENCE AND MECHANISM OF INJURY

The spleen is listed, along with the liver, as either the first or second most commonly injured solid viscus in the abdomen after blunt trauma. Because splenic injuries have a tendency to demonstrate themselves clinically more often than do hepatic injuries, splenic injury was listed as the most commonly injured intra-abdominal solid viscus before the advent of computed tomography (CT) scanning. After the advent of CT scanning and our ability to better diagnose clinically silent intra-abdominal injuries, it became apparent that the liver is also commonly injured and some series now list hepatic injuries as more common than splenic injuries. One large, multi-institutional study showed a 2.6% incidence of splenic injuries (6308 of 227,656 patients) for all patients evaluated for trauma, with splenic injury confirmed by either laparotomy or computed tomography.¹

For penetrating trauma, retrospective reviews of two large centers, Grady Memorial Hospital and Ben Taub General Hospital, showed the incidence of splenic injury from abdominal gunshot wounds to be 7%–9%, far less than for the hollow organs and the liver.^2,3 Injuries to the spleen from stab wounds are even more infrequent.

Splenic bleeding can also occur on a delayed basis, a phenomenon of obvious importance in patients treated nonoperatively. The incidence of delayed bleeding, leading to failure of nonoperative therapy, varies depending on the grade of the injury. The failure rate of nonoperative management in aggregate for a large multi-institutional study was 10.6%, but varied from 4.8% for grade I injuries to 75% for grade V injuries.¹ One hypothesis for the pathophysiology leading to delayed rupture and bleeding is that as subcapsular clot breaks down several days after injury into its component parts, the number of osmotically active particles in the area increases and draws more fluid into the area of injury. The resultant increase in size of the area may then rupture the capsule, leading to renewed bleeding. Even without being trapped under the capsule of the spleen, the inflammation and fibrinolysis in and around the healing injury and clot may weaken the clot enough to result in renewed hemorrhage.

DIAGNOSIS

As with any other trauma patient, the initial management of the patient with splenic injury should follow the ABCs of trauma resuscitation. A particularly important general comment relative to initial resuscitation is that it is important to recognize refractory shock early and treat it with an appropriate operative response.

In the initial history taking, it is important to note any previous operations the patient has undergone, especially a history of splenectomy. History of direct blows to the lower left chest or left upper abdomen, with concomitant pain, may engender suspicion for splenic injury. Any pre-existing conditions that might predispose the spleen to enlargement or other abnormalities also should be ascertained if possible. The patient or significant others should be asked about the presence of liver or portal venous disease, ongoing anticoagulation, propensity for bleeding, or a recent history of aspirin or nonsteroidal anti-inflammatory drug use.

On physical examination, it is important to determine if the patient has left rib pain or tenderness. The left lower ribs are particularly important in that they overlie the spleen, especially posteriorly. In children, the plasticity of the chest wall allows for severe underlying injury to the spleen without the presence of overlying rib fractures. Older patients may not report lower rib pain and may not have particularly noteworthy findings on physical examination in spite of severe chest wall trauma and an underlying splenic injury. Examination of the abdomen can demonstrate localized tenderness in the left upper quadrant or generalized abdominal tenderness, but not all patients with splenic injury will reliably manifest peritoneal or other findings on physical examination. Bleeding without clot formation may not generate peritonitis that can be easily elicited. The unreliability of the physical examination is obvious in patients with altered mental status. As a consequence, imaging of the abdomen in hemodynamically stable patients has become an important element of diagnosis and management.

Diagnostic peritoneal lavage (DPL), once a mainstay diagnostic technique after abdominal trauma, is much less frequently used now. Its role as an initial diagnostic maneuver to dictate subsequent testing or operative intervention has been supplanted in many institutions by ultrasonography and CT scanning of the abdomen. Peritoneal lavage remains useful when ultrasonography is not available or reliable, in that it is a quick way of determining whether a hemodynamically unstable patient is bleeding intraperitoneally.

Ultrasound of the abdomen for free fluid, the so-called FAST (focused assessment with sonography for trauma) examination, is being used increasingly as a means of diagnosing hemoperitoneum in blunt trauma patients. Like DPL, it is most useful in unstable patients. Also, as with peritoneal lavage, the ability of ultrasound to determine exactly what is bleeding in the peritoneal cavity is limited. Attempts to image specific organ injuries using ultrasound have met with limited success. The most common method of using FAST examinations is for detection of intraperitoneal fluid and as a determinant of the need for either further imaging of the abdomen or for emergency surgery (Figure 1).

Figure 1 Focused assessment with sonography for trauma (FAST). Fluid in Morrison’s pouch. The fluid is the dark area between the posteriorly located kidney and the anteriorly located liver (A). Fluid around the spleen in the left upper quadrant. The fluid is the dark area located laterally (B).

CT of the abdomen is the dominant means of nonoperative diagnosis of splenic injury (Figures 2, 3, and 4). Patients are sent either directly for abdominal CT scanning after initial resuscitation or are screened by abdominal ultrasonography as reasonable candidates for subsequent CT. When abdominal CT scanning is done, intravenous contrast is quite helpful in diagnosis; oral contrast is less helpful and does not measurably increase the sensitivity of CT for splenic injury detection.

Figure 2 Computed tomography findings in blunt splenic injury, grade III. The posterior and inferior aspect of the splenic parenchyma is disrupted with the formation of a subcapsular hematoma.

Figure 3 Computed tomography findings in blunt splenic injury, grade IV. A laceration through the parenchyma of the spleen with disruption of the capsule.

Figure 4 Computed tomography findings in blunt splenic injury, grade III. A laceration through the anterior portion of the spleen with a “blush” in the parenchyma.

A CT finding in the spleen that has received a great deal of attention is the presence in the disrupted splenic parenchyma of a “blush,” or hyperdense area with a collection of contrast in it. When present, a blush is thought to represent ongoing bleeding with active extravasation of contrast. There is reasonably convincing evidence that the presence of a blush correlates with an increased likelihood of continued or delayed bleeding from the splenic parenchyma. Such a finding therefore has important implications with respect to either operative intervention or the use of angiographic splenic embolization to stop ongoing bleeding (Figure 5).

Figure 5 Catheter-based management of splenic injury. Computed tomography revealed a grade II splenic injury (A). Evidence of continued bleeding led to angiography. The angiogram demonstrated active extravasation (B), and the injured area was treated with embolization (C).