Anatomic Location of Injury and Injury Grading: American Association for the Surgery of Trauma Organ Injury Scale

Histologically, the spleen is divided into what has been termed red pulp and white pulp. The red pulp is a series of large passageways that filter old red blood cells and also catch 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 IgM.

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. It changes in relative size during maturation. As the child’s bone marrow matures, the spleen becomes relatively less important and diminishes in size relative to the rest of the body. There are also some important differences between pediatric and adult spleens with respect to the splenic capsule and the consistency of the splenic parenchyma. The capsule in children is relatively thicker than it is in adults, and there is also some evidence that the parenchyma is firmer in consistency in children than it is in adults. These two differences have implications for the success of nonoperative management; pediatric patients are more likely to succeed with nonoperative therapy.

It is perhaps not intuitive from the anteroposterior views depicted in anatomy textbooks, but the spleen is normally located quite posteriorly 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. Finally, the spleen is related inferiorly to the distal transverse colon and splenic flexure. The lower pole of the spleen is attached to the colon (splenocolic ligament), and these attachments require division during splenic mobilization. The main arterial blood supply emanates from the celiac axis through the splenic artery, whose course can be somewhat variable along the upper border of the body and tail of the pancreas. The branch points of the splenic artery in the hilum as well as the number of splenic artery branches are also variable. The other sources of arterial blood supply for the spleen are the 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.

A number of different grading systems have been devised to quantify the degree of injury to the spleen. These systems have been created based both on the computed tomographic appearance of ruptured spleens as well as the intraoperative appearance of the spleen. The best known splenic grading system is the one created by the American Association for the Surgery of Trauma (AAST) (Table 1).⁴ Implicit in the AAST grading system are the perhaps fairly obvious concepts that 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 American Association for the Surgery of Trauma Organ Injury Scaling: Splenic Injury Grading

a Advance one grade for multiple injuries, up to grade III.

Adapted from Moore EE, Cogbill TH, Jurkovich GJ, et al: Organ injury scaling: spleen and liver. J Trauma, 38:323, 1995.

The CT and intraoperative appearances of a splenic injury are often different from one another. Some of these differences might be because of evolution of the injury between the time of CT scanning and operation, but it is also likely that CT scanning is imperfect in describing the pathologic anatomy of a splenic rupture. Splenic injury scores based on CT scans can both overestimate and underestimate the degree of splenic injury seen at surgery. It is possible to have a CT appearance of fairly trivial injury but at surgery find significant splenic disruption. Conversely, it is possible to see what looks like a major disruption of the spleen on CT scanning and not see the same kind of severity of injury at surgery. In general, the CT scan and associated scores tend, if anything, to underestimate the degree of splenic injury compared with what is seen at surgery.⁵

An important point about CT-based grading systems is that clinical outcome does not tightly correlate with the degree of injury seen on CT. Although there is a rough correlation between the grade of splenic injury seen on CT scanning and the frequency of operative intervention, exceptions are common. It is possible to have what looks like a fairly trivial injury on CT scan turn out to require delayed operative intervention. In contrast, severe looking splenic injuries on CT scan quite often follow a benign post injury course and are successfully managed nonoperatively.

Probably the major usefulness of splenic organ injury grading, particularly when the AAST Organ Injury Scale is used, is to allow for objective standardization of terminology and to ensure that individual injuries are described in precise terms understandable to others. Standardized organ injury scaling is also useful for describing populations of splenic injury patients and for construction of treatment algorithms.

Nonoperative Management

Appropriate patient selection is the most important element of nonoperative management. Although it is certainly true that nonoperative management is possible in a large number of patients with splenic injury, emergency surgery is still sometimes necessary to stop life-threatening hemorrhage. Of paramount importance in the determination of the suitability of nonoperative management is the hemodynamic stability of the patient. Hemodynamic stability can be a somewhat illusory concept and one for which there is no consensus definition, but hypotension (systolic blood pressure <90 mmHg in an adult) is generally considered worthy of concern. Prehospital or emergency department hypotension is worrisome, and a high index of suspicion for ongoing hemorrhage should be maintained when either is present. In most instances, those patients that remain hemodynamically unstable are inappropriate candidates for abdominal CT scanning. They require either a direct trip to the operating room or, more commonly, abdominal ultrasonography or DPL to determine the presence or absence of intraperitoneal fluid and help guide the initial decision-making process.

Assuming hemodynamic stability, the other important prerequisite for consideration of nonoperative management is the patient’s abdominal examination. In patients who are alert and can provide feedback on physical examination, it is important that they not have diffuse, persistent peritonitis. Although patients with splenic injury often will have abdominal findings secondary to intraperitoneal blood, and localized pain and tenderness in the left upper quadrant are common, obvious diffuse peritoneal signs can be a sign of intestinal injury and warrant abdominal exploration. If a patient with splenic injury is selected for CT scanning and subsequent nonoperative management, it is important to continue to follow the physical examination. If the examination worsens, the possibility of a blunt intestinal injury should be increasingly considered. The most common CT finding in patients with blunt intestinal injury is free fluid in the peritoneal cavity. In patients with damage to the spleen, the free fluid can be mistakenly attributed solely to the splenic injury, and the presence of an associated bowel injury can be missed; the physical examination becomes of even greater importance in such circumstances.

Reported success rates for nonoperative management are 95% or higher for pediatric patients and approximately 80% or higher in adults.^6,7 These high success rates can be misleading, however, in that they apply only to the group of patients in whom nonoperative management was chosen rather than all patients with splenic injury. When immediate splenectomy patients are included, the overall nonoperative management rates tend to be around 50%–60% in adult patients.^1,8 It is also important to remember that these series generally do not include patients in whom the initial impetus was for nonoperative management but in whom emergency surgery was necessary when the patient got into trouble either in the emergency department or during the acquisition of CT scans. The published series of nonoperatively managed spleens generally include only patients who were stable enough to undergo CT scanning and in whom the scan showed a ruptured spleen.

Beyond hemodynamic stability and abdominal findings in the determination of the appropriateness of nonoperative management, other important considerations are the medical environment and some specific characteristics of the patient. Nonoperative management should only be undertaken if it will be possible to closely follow the patient. If close inpatient follow-up is simply not possible, abdominal exploration may be appropriate. Similarly, if rapid mobilization of the operating room and quick operative intervention in the case of ongoing or delayed bleeding is impossible, initial operative intervention may be appropriate.

For patients who are stable enough to undergo CT scanning and in whom a ruptured spleen is seen, nonoperative management is reasonable if they continue to remain stable. In addition to vital signs, one of the other commonly followed parameters in such patients is the hematocrit. A common practice is to determine a cut-off value below which the hematocrit will not be allowed to fall. If the hematocrit drops to that level or below, operative intervention is undertaken. Such an approach works best if there are no associated injuries; when other injuries are present, it can be difficult to know if the spleen is continuing to bleed or if the fall in hematocrit is secondary to bleeding from sites other than the spleen. When contemplating transfusion in patients with splenic injury who are being managed nonoperatively, it should be kept in mind that there is increasingly convincing evidence that transfusion has harmful immunologic effects and is an independent predictor of poor outcome after trauma.⁹

There is some evidence that older patients (>55 years old) might have a worse prognosis with respect to nonoperative management than do younger patients, but there are other reports concluding that outcomes are the same in older versus younger patients.^10,11 Although the evidence in this area is mixed, a relatively recent large multicenter study showed that older patients are more likely to fail nonoperative management, and older patients undergoing nonoperative therapy would likely benefit from earlier conversion to invasive therapy if their condition worsens.¹²

The presence of severe associated injuries, particularly head injury, has been suggested as another relative contraindication to nonoperative management of splenic injury. As previously noted, following the hematocrit in a patient with multiple severe injuries can be problematic. Furthermore, there are concerns about the effects of ongoing or delayed splenic bleeding on the prognosis of a severe head injury. While these factors do not mandate operative intervention in all patients who fall into these groups, they should lower the threshold for operative intervention on an individual basis.

There is little scientific evidence to dictate the specifics of how nonoperative management of splenic injury should be done, and most recommendations are simply matters of common sense and opinion. Most patients should be admitted to an intensive care unit setting for their initial course, including those with grade II or above splenic injuries and patients with multiple associated injuries that make following serial hematocrit levels and physical examinations difficult.

Patients should initially be kept with nothing by mouth in case nonoperative management fails because of significant ongoing bleeding and they require rapid operative intervention, most likely to occur in the early post injury period. Nasogastric suction is not necessary unless needed for other reasons. Bed rest for the patient is somewhat controversial; there is little empirical evidence that it makes a difference. Early mobilization is generally beneficial for trauma patients and should be the practice in patients with splenic injury. Patients should be followed closely hemodynamically, and the urine output should be monitored. Serial hematocrits should be obtained and compared with each other as well as with the admission hematocrit.

Vaccines for meningococcal and streptococcal infection prevention should be given while the patient is observed nonoperatively. There are some theoretical reasons to believe that the vaccinations are more effective if given before splenectomy. It is therefore preferable to vaccinate patients who are managed nonoperatively early in their course rather than waiting to vaccinate them after they have required splenectomy.

The appropriate length of stay in the intensive care unit is not clearly defined. Most centers keep patients with splenic injury in the intensive care unit for 24–72 hours and then transfer them to a ward bed if they have been stable and other injuries permit. At this point, patients are allowed to eat unless other injuries preclude oral intake.

The optimal hospital length of stay is also poorly defined, and there is a variety of practice in this regard. A large multiinstitutional study showed that most failures of nonoperative management occur within the first 6–8 days after injury.¹ Our institutional approach is to keep patients in the hospital for an arbitrary 7 days, picking up the vast majority of delayed bleeding episodes during the inpatient stay.

The issue of follow-up CT scans in patients with nonoperatively managed splenic injuries is also controversial. Most series indicate either they are not necessary or that the frequency with which they alter management is extremely low. Our policy is to study only patients who have persistent abdominal signs and symptoms after a week of observation. On occasion such patients have developed pseudoaneurysms of the spleen, even if the initial CT did not demonstrate a blush. It is difficult to know exactly what the natural history of these pseudoaneurysms would be if left untreated, but they can be impressive in appearance and are amenable to angiographic embolization.

When patients are discharged to home, they should be counseled not to engage in contact sports or other activities where they might suffer a blow to the torso. The best length of time to maintain this admonition is unknown, but typical recommendations range from 2 to 6 months. There is experimental evidence that most injured spleens have not recovered their normal integrity and strength until at least 6–8 weeks post injury, so the recommendation to avoid contact sports for 2–6 months seems reasonable.

Transcatheter Embolization

Embolization of bleeding areas in a ruptured spleen can be an important adjunct to successful nonoperative management. As with nonoperative management in general, patient selection is of paramount importance. Hemodynamic stability is a prerequisite, in that the patient has to be able to tolerate a possibly lengthy diagnostic and therapeutic procedure. There are no consensus guidelines at present for when angiography and embolization are indicated,^13–16 but current trends generally reserve catheter-based interventions for higher grade injuries as well as those with CT evidence of a contrast blush, pseudoaneurysm, arteriovenous fistula, or active extravasation, regardless of the grade of injury.

Operative Management

The best incision for splenic injury, as well as for most trauma operations on the abdomen, is through the midline. Such an approach is versatile, can be extended easily both superiorly and inferiorly, and is also the quickest incision if speed of intervention is important. For operations on an injured spleen, it is often helpful to extend the incision superiorly and to the left of the xiphoid process. This maneuver improves exposure of the left upper quadrant, particularly in large patients and those with a narrow costal angle.

As with all trauma celiotomies, it is important to rapidly examine and pack all four quadrants of the abdomen in patients who are grossly unstable. The initial investigation of the abdomen should not be definitive and should be used only for a quick look at all four quadrants and for packing. While the quadrants are being packed, it is helpful to look for clotting. Clotting tends to localize to the site of injury, whereas defibrinated blood will spread diffusely in the abdomen.

Once attention has been directed to the left upper quadrant, all of the structures in that quadrant should be inspected. There should be an initial look at the greater curvature of the stomach and the left hemidiaphragm. The left hemidiaphragm should be inspected again once the spleen is mobilized if mobilization is necessary. The left lobe of the liver and left kidney should be looked at as well, as should the tail of the pancreas. If the spleen is to be mobilized, inspection of the tail of the pancreas is easier after mobilization has been accomplished.

Splenic mobilization should be done in a stepwise fashion, and the stepwise approach helps in providing adequate mobilization while minimizing the chance of iatrogenic splenic or pancreatic injury. The sequence of splenic mobilization is also important in that it allows for splenic salvage and splenorrhaphy up until the final step of hilar ligation.

The first step in mobilization of the spleen is to cut the lateral attachments of the spleen, the splenophrenic and splenorenal ligaments. This step should be started with sharp dissection and can then be continued with a combination of blunt and sharp dissection. The lateral and superior attachments should be cut to near the level of the esophageal hiatus. Cutting the lateral attachments is sometimes facilitated by putting a finger or clamp underneath them and then bluntly developing the underlying plane before dividing the peritoneum. In large patients and in those with a spleen that is very posterior, it may be necessary to do some of the sharp dissection by feel.

After the lateral attachments have been divided, the next step is to mobilize the spleen and tail of the pancreas as a unit from lateral to medial. One of the easier ways to do this is to place the back of the fingernails of the right hand underneath the spleen and tail of the pancreas so that they are adjacent to the underlying left kidney. The kidney can be palpated easily because it is firm and provides an excellent landmark for the proper plane of dissection. A common error is to try to mobilize the spleen alone without the adjacent pancreas, thus limiting the degree of splenic mobility and making it more difficult to avoid iatrogenic injury to the spleen and pancreatic tail. The splenic hilum can be injured during mobilization from lateral to medial; the pancreatic tail can be inadvertently included in the hilar clamping of the spleen. Both problems are minimized with optimal mobilization and visualization.

After the spleen and pancreas have been mobilized as a unit, it is generally apparent that the next constraining attachments of the spleen are the short gastric vessels. Because of the dual blood supply of the spleen though its hilum and also through the short gastric vessels, it is possible to divide the short gastric vessels without compromising splenic viability. The best way to divide the short gastric vessels is to have an assistant elevate the spleen and tail of the pancreas into the operative field and then to securely clamp the vessels starting proximally on the greater curvature of the stomach. The short gastric vessels, as the name implies, are short. It is therefore not uncommon to be concerned about a clamp on the gastric portion of a short gastric vessel having included a small portion of stomach. In such cases, the tie on the short gastric vessels and nubbin of stomach can necrose the stomach, leading to a delayed gastric leak. This concern can be addressed by oversewing any gastric areas in question.

The final step necessary for full mobilization of the spleen is division of the splenocolic ligamentous attachment between the lower pole of the spleen and the distal transverse colon and splenic flexure (Figure 6). During division of both the short gastric vessels and the splenocolic ligament, bleeding from the spleen can be controlled using digital compression of the hilum. If the patient is exsanguinating and the bleeding is massive, a clamp can be placed on the hilum during the later steps of mobilization. Mass clamping should only be done in extreme circumstances, however, because it increases the chances of injury to the tail of the pancreas (Figure 7).

Figure 6 The spleen is grasped and the lateral peritoneal ligaments are divided. The splenocolic ligaments have been divided to release the splenic flexure.

(From Khatri V, Asensio JA: Operative Surgery Manual. Philadelphia, WB Saunders, 2002, p. 189.)

Figure 7 After complete mobilization of the spleen, the vessels at the hilum are clamped and divided, avoiding injury to the tail of the pancreas.

(From Khatri V, Asensio JA: Operative Surgery Manual. Philadelphia, WB Saunders, 2002, p. 189.)

After the spleen has been fully mobilized, it is possible to inspect it in its entirety. It is also possible to examine the posterior aspect of the body and tail of the pancreas. It is helpful after mobilization to pack the splenic fossa to tamponade any minor bleeding and also to help keep the spleen and distal pancreas elevated into the field. During this packing maneuver, the left adrenal gland can be inspected and the left hemidiaphragm re-examined.

If the injury is small and bleeding minimally, topical hemostatic agents can be used and the spleen returned to its normal position. Electrocautery is rarely helpful. Argon beam coagulators have shown promise in animal models of splenic injury. If the injury is more severe and the patient’s overall condition is not too serious, splenorrhaphy can be done, although with the advent of nonoperative management the number of splenic injuries found at surgical intervention that are amenable to repair has decreased. The spleen can be sutured, especially when there is an intact capsule, but it does not hold sutures particularly well and it is advisable therefore to use pledgets. Wrapping of either all or part of an injured spleen with absorbable mesh can also be done, but these techniques are moderately time consuming. Partial splenectomy has been described and is possible because of the segmental nature of the splenic blood supply. The blood supply to the damaged portion can be ligated and the spleen observed for its demarcation. The nonviable portion is removed with the exposed parenchyma made hemostatic either with suture or mesh wrapping.

Splenectomy should be done in patients who are unstable or who have serious associated injuries. It should also generally be done for the highest grades of splenic injury (IV to V) if operative management has been chosen. The hilar structures should be addressed with serial dissection and division. Suture ligation should be used for large vessels.

Drains should not be routinely placed after either splenectomy or splenorrhaphy and may actually increase the rate of postoperative complications. Drainage is reasonable if there is associated pancreatic injury or an associated renal injury when there is concern about postoperative urine leak.