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Splenic injuries
The proclivity for the spleen to bleed from blunt abdominal trauma was not lost on the Thuggee cult. A group of professional assassins who existed from the 13th to 19th centuries in India, they murdered others to worship Kali, a Hindu goddess of destruction. They often targeted blunt trauma to the left upper quadrant of their victims. This is where the spleen, often fragile and swollen from malaria, lay. In the absence of blood transfusion and modern surgery, these blows often proved fatal.
As our understanding of splenic injury increased, management strategies evolved from routine aggressive operative management to nonoperative management with or without embolization. Safe selection criteria for nonoperative management continues to be more tightly refined. Despite the increase in incidence of nonoperative management, it is important to keep in mind that splenic injuries can bleed to death just as they did in the time of the Thuggee.
Incidence and mechanism of injury
The spleen is frequently listed as either the first or second most commonly injured solid abdominal organ following blunt trauma. A 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 imaging.
Splenic injuries occur via three mechanisms: penetrating, blunt, and indirect trauma. Retrospective reviews of two large urban trauma centers, Grady Memorial Hospital and Ben Taub General Hospital, demonstrated the incidence of splenic injury from abdominal gunshot wounds to be 7% to 9%. Injuries to the spleen from stab wounds are even less frequent.
Blunt splenic injuries can bleed immediately or in a delayed basis. In delayed splenic bleeds, a subcapsular clot lyses into osmotically active particles, which draws fluid into the capsule days after injury. Eventually, the forces of swelling exceed the tensile strength of the capsule, leading to rupture and renewed bleeding. A simpler explanation posits the inflammation around the healing injury can directly weaken the clot enough to result in renewed hemorrhage.
A third mechanism of injury to the spleen is indirect trauma, specifically during colonoscopy. Traction on the splenocolic ligament causes a tear in the splenic capsule. Although this is a rare injury mechanism, it has a reported mortality rate of 5% and requires the same management algorithm used in other types of splenic trauma.
Diagnosis
The initial management of the patient with splenic injury follows the ABCs (airway, breathing, and circulation) of trauma resuscitation. It is important to quickly identify transient or nonresponders to volume resuscitation. Early operative intervention is required following the diagnosis of refractory shock lest risk preventable morbidity and mortality.
Previous abdominal operations, preexisting medical conditions that predispose to splenomegaly, including cirrhosis or lymphomas, and usage of anticoagulants or antiplatelet medications are important components of the patient’s history.
On physical examination, left posterior rib tenderness may signal an underlying splenic injury. In children with elastic chest walls, the absence of overlying rib fractures is not sufficient to rule out splenic injury. Examination of the abdomen can demonstrate localized left upper quadrant or generalized abdominal tenderness. It is important to remember that not all patients with splenic injury will reliably manifest peritoneal findings. Bleeding without clot formation may not generate peritonitis. Other patients may be altered from blunt head trauma or intoxicants.
Imaging in the unstable blunt abdominal trauma patient is initially performed by focused assessment with sonography in trauma. It is useful as a means of diagnosing intra-abdominal bleeding as the responsible agent for hemodynamic instability. It cannot determine which intra-abdominal organ is bleeding. In this binary decision branch point, the patient will proceed to either the operating room for emergency surgery (positive) or to CT imaging of the abdomen (negative) ( Fig. 1 ).
CT of the abdomen with intravenous contrast alone is imaging modality of choice to diagnosis splenic injury ( Figs. 2–4 ). In addition to providing the injury grade, associated injuries, and degree of hemoperitoneum, it also can determine the presence of a “blush,” a hyperdense extravasation of contrast agent that represents ongoing bleeding. The presence of a blush may correlate with an increased likelihood of ongoing or delayed bleeding. However, in the initial management of the hemodynamically stable patient, the presence of a blush does not mandate operative intervention. It should heighten concerns about failure of nonoperative management with consideration to angiography and embolization ( Fig. 5 ).
Anatomic location of injury and injury grading: American association for the surgery of trauma organ injury scale
It is perhaps not intuitive from the anteroposterior views depicted in anatomy textbooks, but the spleen is located more posterior than imagined in the upper abdomen. It is covered by the peritoneum except at the hilum. Posteriorly and laterally, the spleen is related to the left hemidiaphragm and the left posterior and posterolateral lower ribs. The lateral aspect of the spleen is attached to the posterior and lateral abdominal wall and the left hemidiaphragm (splenophrenic ligament) with a variable number of attachments; these require division during mobilization of the spleen. Posteriorly, the spleen is related to the left iliopsoas muscle and the left adrenal gland. Posteriorly and medially, the spleen is related to the body and tail of the pancreas, and it is quite helpful to mobilize the tail and body of the pancreas along with the spleen when elevating the spleen out of the left upper quadrant. Medially and to some extent anteriorly, the spleen is related to the greater curvature of the stomach. Posteriorly and inferiorly, the spleen is related to the left kidney. There are attachments between the spleen and left kidney (splenorenal ligament) that require division during mobilization. Inferiorly, the lower pole of the spleen is attached to the distal transverse colon (splenocolic ligament), and these attachments require division during splenic mobilization.
The main arterial blood supply to the spleen is from the celiac axis through the splenic artery. Its course is variable along the upper border of the body and tail of the pancreas. The location and number of branches of the main splenic artery into segmental arteries is inconstant as well. An additional source of arterial blood supply is via short gastric vessels that connect the left gastroepiploic artery and the splenic circulation along the greater curvature of the stomach. The venous drainage of the spleen is through the splenic vein and the short gastric veins.
Histologically, the spleen is divided into red pulp and white pulp. The red pulp is a series of large passageways that filter old red blood cells and bacteria. The filtering of bacteria in the interstices of the red pulp allows the antigens of the bacterial walls to be presented to lymphocytes in the adjacent white pulp. The white pulp is filled largely with lymphocytes located such that they can be exposed to antigens either on microorganisms or moving freely in the circulation. Lymphocyte exposure to antigens results in the production of immunoglobulins, the most common of which is immunoglobulin M.
Embryologically, the spleen develops initially as a bulge on the left side of the dorsal mesogastrium and begins a gradual leftward migration to the left upper quadrant. During childhood, the capsule is relatively thicker, and the parenchyma is firmer in consistency. than it is in adults. These two differences may explain the relatively greater success of children with nonoperative management.
The most widely accepted injury grading system for splenic injuries is the American Association for the Surgery of Trauma Organ Injury Scale ( Table 1 ). This is a CT-based grading system in which the grade increases with an increase in either the length or depth of parenchymal injury, injury to the hilum, or injuries to multiple areas of the spleen.
TABLE 1
AAST-OIS: Splenic Injury Grading
Modified from Moore EE, Cogbill TH, Jurkovich GJ, et al: Organ injury scaling: spleen and liver. J Trauma 38:323, 1995.
| Grade * | Injury Type | Description of Injury |
|---|---|---|
| I | Hematoma | Subcapsular, <10% surface area |
| Laceration | Capsular tear, <1 cm parenchymal depth | |
| II | Hematoma | Subcapsular, 10%–50% surface area |
| Laceration | Capsular tear, 1 to 3-cm parenchymal depth that does not involve a trabecular vessel | |
| III | Hematoma | Subcapsular, >50% surface area or expanding; ruptured subcapsular or parenchymal hematoma; intraparenchymal hematoma 5 cm or expanding |
| Laceration | >3-cm parenchymal depth or involving trabecular vessels | |
| IV | Laceration | Laceration involving segmental or hilar vessels producing major devascularization (>25% of spleen) |
| V | Laceration | Completely shattered spleen |
| Vascular | Hilar vascular injury that devascularizes spleen |
AAST-OIS, American Association for the Surgery of Trauma Organ Injury Scaling.
Grading systems allow for standardization of terminology in which to communicate precise and understandable terms to others. They allow for the construction of treatment algorithms (if grade x, proceed with y intervention) and multi-institutional research initiatives.
However, the radiographic and intraoperative appearances of a splenic injury are often different from one another. This may be due, in part, to the temporal evolution of the injury between imaging and laparotomy, but it is also true that imaging is inherently imperfect in describing the pathologic anatomy of a splenic injury. More commonly, the CT scan and associated injury severity scores tend to underestimate the degree of splenic injury seen at the time of operation.
Additionally, although there is a rough correlation between the grade of splenic injury seen on CT scans and the frequency of operative intervention or rates of nonoperative management failure, exceptions are common. For example, a patient with low-grade or near-normal index CT scans presenting with a delayed splenic bleed has been previously described.
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