Injury to the Spleen
The spleen is listed, along with the liver, as either the first or second most commonly injured solid viscus in the abdomen. 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 prior to 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. Therefore, some current series list hepatic injuries as more common than splenic injuries.
During the past 50 years, there has been increasing interest in the notion that not all splenic injuries require splenectomy. Although evolution has steadily moved us away from routine aggressive operative management, it is important to always keep in mind that splenic injuries can be deadly and that patients with splenic injury can bleed to death.
HISTORICAL PERSPECTIVE
The spleen has been subject to injury for as long as man has suffered trauma. In ancient India, where malaria was endemic and large and fragile spleens were commonplace, intentional injury of the spleen was a method of assassination (F. William Blaisdell, MD, Sacramento, CA, 1985, personal communication). Paid assassins called thuggee carried out their mission by delivering a blow to the left upper quadrant of the intended victim. They hoped to cause splenic rupture, for which there was no treatment at that time. If the rupture was severe enough, the victim would bleed to death. As we know from our current imaging capabilities and management protocols, the thuggees must have been frustrated on occasion by the lack of success of their attempted assassinations.
The spleen was felt by the ancient Greeks and Romans to play a significant role in human physiology. Aristotle thought that the spleen was on the left side of the body as a counterweight to the right-sided liver.1 He believed that the spleen was important in drawing off “residual humors” from the stomach. The close relation of the stomach and spleen and the presence of the short gastric vessels so important in present-day splenic mobilization likely encouraged this belief. The spleen was also felt to “hinder a man’s running,” and Pliny reportedly claimed that “professed runners in the race that bee troubled with the splene, have a devise to burne and waste it with a hot yron.”2 The exceptional speed of giraffes was felt to be related to the erroneous belief that giraffes were asplenic. Early references to removal of the spleen to increase speed make it apparent that it has long been known that the spleen is not absolutely necessary to sustain life. Paracelsus believed that the spleen could be removed and rejected the notion that it was important for the storage of “black bile.”3
In 1738, John Ferguson of Scotland removed a portion of the spleen through an open wound in the left side (Fig. 30-1).3 Once the era of abdominal surgery had begun, it was discovered that the spleen could be removed with what seemed like relative impunity. Mayo reported in 1910 that “the internal secretion of the spleen is not important, as splenectomy does not produce serious results.”4 Although some suggested that the spleen was important in some way for immune function and for the removal of senescent red blood cells, it was not felt that these functions were of great importance. Until several decades ago, this resulted in a philosophy in which any traumatic splenic injury, no matter how trivial, was treated with splenectomy.3,4 Even small iatrogenic injuries occurring during elective surgery were treated with splenic removal.
FIGURE 30-1 A depiction of the partial splenectomy done by John Ferguson of Scotland and reported in 1738. The operation actually had been done some years earlier. (Reproduced with permission from Hiatt JR, Phillips EH, Morgenstern L, eds. Surgical Diseases of the Spleen. New York: Springer-Verlag; 1997:6.)
There were some early thoughts that the spleen played a role in combating infection, but it only has been in the last century that our understanding of the role of the spleen in immune function has developed.5,6 The initial clinical impetus to more closely examine the immunologic role of the spleen was based on the observation that neonates and infants who required splenectomy for hematologic disease suffered otherwise inexplicably high rates of postoperative mortality from overwhelming infection. Pneumonia and meningitis secondary to pneumococcus and other encapsulated organisms were particularly common. The dramatic consequences of splenectomy in this very specific group of patients led to the investigation of the effects of splenectomy in pediatric trauma patients. Although the evidence for severe immunologic consequences of splenectomy in this group was less convincing than in pediatric patients with hematologic disease, there was a strong inference that splenectomy for trauma would lead to an increased rate of overwhelming sepsis, just as occurred after splenectomy for hematologic disease. Cases of overwhelming postsplenectomy sepsis in adults who had undergone splenectomy for trauma were reported, also.7,8
Several other developments that paralleled our increased understanding of the importance of the spleen for immune function were the development of improved abdominal imaging and increasing questions about the safety of transfused blood. The advent of CT scanning of the abdomen and its continued improvement in quality markedly increased our ability to diagnose splenic injury nonoperatively, and it became apparent that clinically silent splenic injuries could occur. Concerns about the safety of stored blood transfusion with respect to hepatitis and human immunodeficiency virus, however, led to increasing questions about transfusions for patients with splenic injury.
Most splenic injuries are obviously due to the same blunt and penetrating mechanisms that cause other traumatic injuries. Increased use of percutaneous procedures and abdominal ultrasound has revealed more obscure mechanisms such as colonoscopic manipulation and placement of a nephrostomy tube as potential causes of splenic injury.9,10
SPLENIC FUNCTION
Histologically, the spleen is divided into what has been termed red pulp and white pulp.11 The red pulp is a series of large passageways that filter old red blood cells and trap bacteria, also. Filtering is important in removing poorly functioning senescent red blood cells from the bloodstream and keeping the hematocrit and blood viscosity within a normal range. The trapping of bacteria in the filters of the red pulp allows the antigens of the bacterial walls to be presented to the 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 circulating freely in the circulation. Lymphocyte exposure to antigens results in the production of immunoglobulins, the most common of which is IgM.11,12 Other potentially important functions of the white pulp are the production of opsonins such as tuftsin and properdin and complement activation in response to appropriate stimuli.
All these functions of the spleen are, of course, lost after splenectomy. Collections of lymph tissue are also found in the liver, thymus, intestinal tract, and skin, and these areas may take over some of the functions of the spleen after splenectomy. In addition, some of the necessary functions of the spleen could conceivably be carried out by accessory spleens, but the removal of the spleen results in loss of most filtering and immune functions. How serious these losses are to normal function is a matter of debate. The loss of the filtering function of senescent red blood cells seems to be tolerated reasonably well. Although certain kinds of senescent red blood cells in the bloodstream are more pronounced after splenectomy, the normal production and removal of red blood cells seems, for the most part, to continue. The loss of splenic function has been the subject of a great deal of investigation. A study of isolated splenic injuries revealed an early postinjury infection rate of 9% in postsplenectomy patients as opposed to a rate of only 2% in patients successfully managed nonoperatively. There is also evidence of an increased incidence of overwhelming sepsis after splenectomy for trauma, but the precise incidence of such overwhelming infections, especially in adults, is so low that it is difficult to quantify.13
The possibility that small accessory spleens might provide residual splenic function raises the question of how much splenic mass is necessary for the filtering and immune functions of the spleen. This is a question of more than academic importance, in that a variety of techniques have been described for partial splenectomy or autotransplantation of the spleen after splenectomy.14,15 The exact amount of spleen to reimplant after splenectomy or leave behind after partial splenectomy is dependent on the minimum amount of splenic tissue necessary for normal function. How much spleen is necessary for normal function is not precisely known, but is thought to be between 30% and 50%.16
SPLENIC ANATOMY
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. In children, it is large because it is necessary for both reticuloendothelial function and production of red blood cells. 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 some evidence that the parenchyma is firmer in consistency in children than it is in adults, as well. These two differences have implications for the success of nonoperative management. A thicker capsule and tougher parenchymal consistency imply that pediatric spleens are more likely to survive an insult without major bleeding and the need for operative intervention. This is part of the explanation for why children are more often candidates for nonoperative management than are adults and why nonoperative management tends to be somewhat more successful in children than it is in adults.
The normal adult spleen ranges in size from 100 to 250 g. A number of disease processes, however, can change both the size and consistency of the spleen. Malaria and its effects on the spleen with respect to enlargement and changes in consistency have already been referred to earlier. Hematologic diseases such as lymphoma and leukemia can also change both the size and consistency of the spleen and make it more susceptible to damage. Other more common diseases such as mononucleosis make the spleen more vulnerable to injury. An equally important and prevalent pathology that can increase splenic vulnerability is portal venous hypertension. Usually such portal hypertension is secondary to cirrhosis of the liver and, when it is present, the spleen can become both enlarged and less firm in consistency.
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 (Fig. 30-2). 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 that require division during mobilization of the spleen. The extent of these attachments is quite variable. Minimal attachments result in a fairly mobile spleen while thick attachments, when present, require sharp dissection. The lateral attachments tend to be smaller and less extensive in children than in adults. As the spleen lies adjacent to the posterior ribs on the left side, left posterior rib fractures should increase the index of suspicion for underlying splenic injury. Because of the close relation of the spleen to the diaphragm, simultaneous injuries to the two structures are not uncommon (see Chapter 28). After penetrating trauma, a knife or bullet can obviously injure both the left hemidiaphragm and the spleen. The diaphragm can also be injured in blunt trauma, and the spleen, either injured or uninjured, can herniate through a diaphragmatic defect into the left pleural space. The diaphragm should always be closely inspected during surgery for splenic injury.
FIGURE 30-2 The spleen is located quite posteriorly in the left upper quadrant and is attached to surrounding structures by a variety of ligaments. (Reproduced with permission from Carrico CJ, Thal ER, Weigelt JA, eds. Operative Trauma Management: An Atlas. Norwalk, CT: Appleton & Lange; 1998. Copyright The McGraw-Hill Companies, Inc.)
Posteriorly, the spleen is related to the left iliopsoas muscle and the left adrenal gland. The left adrenal gland is usually fairly small and has a characteristic yellow-gold color. It tends to be related to the posterior aspect of the superior portion of the spleen and should be protected when seen during splenic mobilization.
Posteriorly and medially, the spleen is related to the body and tail of the pancreas. Therefore, it is very helpful to mobilize the tail and body of the pancreas along with the spleen when elevating the spleen out of the left upper quadrant as this increases the extent to which the spleen can be mobilized.
Medially and to some extent anteriorly, the spleen is related to the greater curvature of the stomach. This relation is important in that the spleen can receive a variable amount of blood supply from the greater curvature via short gastric branches from the left gastroepiploic artery. The short gastric vessels require division during full mobilization of the spleen.
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 of the spleen. The left kidney should be left in place while mobilizing the spleen and tail of the pancreas from lateral to medial. There are exceptions to leaving the kidney in place, most notably if the kidney also has been injured or if mobilization of the spleen is being done to provide exposure to the aorta from the left side (see Chapter 36).
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 splenic artery, one of the major branches of the celiac axis, courses along the superior aspect of the body and tail of the pancreas toward the splenic hilum. Although generally located along the upper border of the body and tail of the pancreas, its course can be somewhat variable. The splenic artery is commonly quite tortuous, as well. It divides into a variable number of branches that provide a segmental blood supply to the spleen. Both the number of branches and the site at which the branching occurs are quite variable (Fig. 30-3). This variability is of surgical significance in that there is no absolute and dependable number of splenic artery branches that require division during splenectomy or segmental resection of the spleen. Most commonly, a number of separate splenic artery branches are ligated during splenectomy rather than a single ligation of the main splenic artery. It is possible to find the splenic artery along the superior margin of the body and tail of the pancreas if necessary, and sometimes it is helpful to ligate the artery at that location even after hilar branches have been ligated if the surgeon is interested in extra hemostasis.
FIGURE 30-3 The arterial blood supply to the spleen can be quite variable. The most common configuration consists of two extraparenchymal divisions of the splenic artery (upper left figure).
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. There is an average of four to six short gastric arteries. As implied by their name, these branches off the greater curvature are generally fairly short and are easily injured during mobilization of the spleen.
The venous drainage of the spleen, like the arterial inflow, is via two routes. The splenic vein drains the spleen via a number of branches that coalesce to form a single large vein that courses along the posterior aspect of the body and tail of the pancreas to its confluence with the superior mesenteric vein. Like venous anatomy elsewhere in the body, the location, size, and branches of the splenic view can be quite variable. The other route of splenic venous drainage is via short gastric veins that course adjacent to the short gastric arteries. They drain into the left gastroepiploic vein during its course along the greater curvature of the stomach.
PATHOPHYSIOLOGY OF INJURY
Although nonoperative management is often appropriate after splenic injury, many patients with splenic injury still need emergency surgery to stop the bleeding. In a large multi-institutional survey, approximately 45% of patients with splenic injury required emergency surgery.17 A study using rigid predefined criteria for nonoperative management revealed that 33% of isolated blunt splenic injuries require immediate operation and a further 23% treated with initial nonoperative management required operation, for an overall 56% operative rate.18 Overall operative rates vary depending on setting, with higher operative rates for rural and nonteaching hospitals.19 The higher operative rate in smaller hospitals may in part be due to different management philosophies. Also, it is related to the fact that large referral hospitals see a higher percentage of transferred patients who have already withstood the test of time and have proven themselves good candidates for nonoperative management. The rate also varies when comparing large multi-institutional series with single institutional series. Regardless of the setting, however, it is clear that rapid operative intervention is sometimes necessary. This is particularly true when patients have a coagulopathy either from pre-injury anticoagulation or as a consequence of their injury.
Bleeding can also be a problem on a delayed basis.20,21 The concept of “delayed rupture” of the spleen is in some ways a misnomer. The initial notion that the spleen could bleed on a delayed basis dates back to an era before abdominal CT scanning. In that era, it was observed that some patients who had suffered a traumatic injury did not manifest overt bleeding from their spleen for a number of days or sometimes even weeks or months after the traumatic event. With the advent of abdominal CT scanning, it became apparent that these were probably cases of “delayed bleeding” rather than that of delayed rupture. The distinction between these two entities is more than academic. If “delayed rupture” of the spleen can occur without much evidence of preexisting injury, CT scanning of the abdomen shortly after injury would be negative. In this case, there would be no good way to screen patients and make sure that they were not at risk for delayed splenic bleeding. In contrast, if what used to be called delayed rupture is actually just delayed bleeding, early diagnosis of the presence of the splenic injury should allow us to tailor our management such that the risk of the delayed bleeding is minimized.
Penetrating injuries to the spleen are most commonly managed operatively, often because of concerns about associated intraperitoneal injuries. Concerns about injury to the diaphragm from the knife or bullet are a common rationale for operative intervention in patients with penetrating injury to the spleen, also. Operative intervention, of course, does not mandate splenectomy after penetrating injury any more than it does after blunt injury, although the risk of major arterial disruption after penetrating trauma is somewhat higher than after blunt trauma. Attempts at splenic salvage are appropriate after blunt or penetrating splenic injury, especially if the grade of injury is low and associated injuries are not particularly severe.
INITIAL EVALUATION AND MANAGEMENT
As with any other trauma patient, the initial management of the patient with splenic injury should follow the airway, breathing, and circulation (ABCs) of trauma evaluation and resuscitation (see Chapter 10). 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. There are some aspects of the initial evaluation, with respect to the spleen, that deserve special mention:
1. The possibility of an additional intra-abdominal injury in patients with splenic injury seen on CT scanning should be kept in mind. Injury to the gastrointestinal tract is of particular concern.
2. While operating on patients with splenic injury, it is important to look for associated injuries, particularly to the left hemidiaphragm and the pancreas.
3. When mobilizing the spleen, always mobilize the tail of the pancreas medially with the spleen to optimally expose the splenic hilum and minimize risk to the spleen and pancreas.
4. Despite the fact that nonoperative management of splenic injury is a commonly successful strategy, patients can still bleed to death from splenic injury. Therefore, a significant percentage of patients still require surgical intervention and splenectomy.
Elements of the history may be helpful in the diagnosis of splenic injury, and mechanism of injury is important. In patients injured in a motor vehicle crash, the position of the patient in the car can be of some importance in diagnosing splenic injury. Victims located on the left side of the car (drivers and left rear passengers) are perhaps slightly more susceptible to splenic injury because the left side of their torso abuts the left side of the car. This does not mean, however, that victims in other locations in a vehicle are not at risk. For patients who have suffered penetrating injury, the type and nature of the weapon is important. When possible, it is helpful to know the caliber of the gun or the length of the knife (see Chapter 1).
In the initial history taking, it is important to note any previous operations the patient has undergone. Of particular importance are any operations that may have resulted in splenectomy (i.e., previous operations for hematologic disease or abdominal trauma). Any preexisting conditions that might predispose the spleen to enlargement or other abnormality should be asked about, as well. The patient or significant others should be asked about the presence of hepatic disease, ongoing anticoagulation, or recent usage of aspirin or non-steroidal anti-inflammatory drugs, also.
On physical examination, it is important to determine if the patient has left rib pain or tenderness. Left lower ribs are particularly important in that they overlie the spleen, especially posteriorly. Approximately 14% of patients with tenderness over the left lower ribs will have a splenic injury. Even with tenderness over the left lower ribs as their only indication of possible abdominal injury, 3% of patients will have a splenic injury.22 In children, the plasticity of the chest wall allows for severe underlying injury to the spleen without the presence of overlying rib fractures. Such a phenomenon is also possible in adults, but is less common than it is in children.
The absence of tenderness over the left lower ribs does not preclude the presence of an underlying splenic injury and, in some cases, may be related to an altered level of consciousness from an associated traumatic brain injury or intoxication. In elderly patients, rib fractures may not manifest in a fashion similar to that seen in younger patients. Patients over the age of 55 may not describe lower rib pain and may not have particularly noteworthy findings on physical examination in spite of severe trauma to the chest wall and an underlying splenic injury.
Another finding on physical examination that is occasionally helpful in the presence of a splenic injury is the presence of Kehr’s sign. Kehr’s sign is the symptom of pain near the tip of the left shoulder secondary to pathology below the left hemidiaphragm. There is minimal shoulder tenderness, and the patient typically does not have pain on range of motion of the left arm and shoulder unless there is an associated musculoskeletal injury. Kehr’s sign after splenic injury is the result of irritation of the diaphragm by subphrenic blood. The innervation of the left hemidiaphragm comes from cervical roots 3, 4, and 5, the same cervical roots that innervate the tip of the shoulder, and referred pain from the diaphragmatic irritation causes the left shoulder pain. Although it is relatively uncommon, the presence of Kehr’s sign shortly after trauma should increase the index of suspicion for splenic injury.
The physical examination of the abdomen sometimes demonstrates 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. Ecchymoses or abrasions in the left upper quadrant or left lower chest may be present, also. The unreliability of the physical examination of the abdomen is obvious in patients with an altered mental status and may be absent in patients with normal mentation, as well. As a consequence, imaging of the abdomen in hemodynamically stable patients has become an important element of diagnosis and management (see Chapter 15).
There are no laboratory studies specific to patients with splenic injury, although a hematocrit and typing and cross-matching of blood are useful initial laboratory tests. Coagulation studies may be warranted if there is reason to believe that the patient is coagulopathic. As with all other early post-traumatic bleeding, bleeding from a splenic injury in the early postinjury period will not always cause a marked drop in hematocrit. An extremely low hematocrit on arrival of the patient in the resuscitation room, however, especially if the transport has been short and prehospital fluid resuscitation has been minimal, should alert the surgeon to the possibility of severe ongoing hemorrhage (see Chapter 10).
Plain x-rays generally are not helpful in the diagnosis of splenic injury. Rupture of the left hemidiaphragm is sometimes apparent on an initial chest x-ray, however, and can suggest an associated splenic injury. A severe pelvic fracture on an anteroposterior pelvic film can sometimes be of importance in subsequent decision making about how to manage a splenic injury as the presence of simultaneous splenic and severe pelvic injuries often will dictate the removal of the spleen. When penetrating trauma is the mechanism of injury, an initial chest x-ray is important in ruling out associated thoracic injury and, in the case of gunshot wounds, helping to determine the path of a bullet and the location of a retained bullet or bullet fragments.
IMAGING AND DIAGNOSTIC PERITONEAL LAVAGE
Diagnostic peritoneal lavage (DPL) is used much less frequently now. Its role as an initial diagnostic maneuver to dictate subsequent testing or operative intervention has been supplanted in many institutions by both ultrasonography and CT scanning of the abdomen (see Chapters 15 and 16). Peritoneal lavage remains useful when ultrasonography is not available, however, in that it is a quick way of determining whether or not a hemodynamically unstable patient is bleeding intraperitoneally. Although DPL is not specific for splenic injury, splenic injuries with ongoing bleeding result in a positive peritoneal lavage most of the time that prompts timely operative intervention. When there is an associated diaphragmatic injury, however, DPL may not yield positive results. Because the instilled fluid may be retained in the pleural space, a diaphragmatic injury should be considered when the DPL yields little or no return of fluid.
Ultrasound of the abdomen for free fluid, the so-called FAST exam, is being used increasingly as a means of diagnosing hemoperitoneum in patients with blunt trauma (see Chapter 16). 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. Small injuries and subcapsular hematomas of the spleen can also be missed by ultrasonography if they do not result in a significant hemoperitoneum. There have been attempts to use ultrasound not only to diagnose intraperitoneal fluid but also to diagnose specific injuries such as splenic injuries. Such attempts have met with limited success, and the most common method of using FAST exams is for detection of intraperitoneal fluid and as a determinant of the need for either further imaging of the abdomen or emergency surgery.
CT scanning of the abdomen is the dominant means of nonoperative diagnosis of splenic injury. Patients are either sent directly for abdominal CT scanning after initial resuscitation or 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 much less helpful and does not increase the sensitivity of CT for detecting a splenic injury. Radiation exposure from CT, especially in children, has been raised as a potential concern and some selection should be used with respect to which patients with abdominal trauma should undergo scanning.23 Undue concern about radiation, however, should not put a patient at risk for a missed splenic injury and occult bleeding.
The findings of splenic injury on CT scan are variable (Fig. 30-4). Hematomas and parenchymal disruption generally show up as hypodense areas. Free fluid can be seen either around the spleen or throughout the peritoneal and pelvic spaces. Locations where fluid frequently accumulates after splenic injury are Morison’s pouch, the paracolic gutters, and the pelvis. When a large amount of fluid is present in the peritoneal cavity, it can sometimes be seen between loops of small bowel as well as in the subphrenic spaces.
FIGURE 30-4 Computed tomographic findings in a patient with a ruptured spleen. The splenic parenchyma is disrupted, and there is some blood and hematoma. There is also a splenic “blush” in the disrupted parenchyma.
When looking at CT scans of patients with splenic injury, it is also important to look at the adjacent left kidney and the distal pancreas. Injury to the spleen implies a blow to the left upper quadrant that can also injure the adjacent organs. The diagnosis of a pancreatic injury is particularly important in that this can significantly affect the patient’s subsequent course and prognosis. Also, it is important to remember that the presence of free fluid is not solely related to bleeding from a visible splenic injury in all cases. One of the pitfalls of CT diagnosis is that free fluid in the peritoneal cavity or in the pelvis may be attributed to a splenic injury when in fact the fluid is secondary to both a splenic injury and an associated injury to the mesentery or bowel.
Other than an obvious injury, the most important CT finding in the spleen is the presence in the disrupted splenic parenchyma of a “blush,” or hyperdense area with a concentration of contrast in it (Fig. 30-4). When seen, a blush is thought to represent ongoing bleeding with active extravasation of contrast. There is evidence that the presence of a blush correlates with an increased likelihood that continued or delayed bleeding will occur. A pseudoaneurysm of a branch of the splenic artery is evidence that the vessel has been damaged, as well. These arterial injuries need further assessment with either angiography or repeat CT scanning.
In addition to the above findings, incidental findings such as cysts and granulomas are occasionally seen on CT. Primary cysts are parasitic (rare in the United States), congenital, or neoplastic. Secondary cysts (those without an epithelial lining) may result from trauma or infarction.
A number of scoring systems have been devised to describe the degree of splenic injury seen on CT scanning.24–27 Some of these scoring systems will be described in further detail later. It is important to remember, however, that there is not a perfect correlation between the grade of splenic injury seen on CT scanning and the grade of splenic injury seen at the time of surgery in patients who require operative intervention. Also, it is important to remember that the CT grade of splenic injury and a patient’s subsequent clinical course are only roughly correlated.
Magnetic resonance imaging (MRI) has been used sporadically in the diagnosis of splenic injury (see Chapter 15). The images obtained are sometimes quite impressive but, given that CT scanning has both a very high sensitivity and specificity for the presence of splenic injury (especially when newer-generation multidetector scanners are used), MRI so far has not proven to be an obvious improvement. Furthermore, MRI is usually less available than is CT scanning, especially after hours. The logistical difficulties inherent in trying to obtain magnetic resonance images in a badly injured patient who requires close monitoring and possibly even mechanical ventilation make MRI even less helpful as a diagnostic modality. Continued improvements in MRI and our increasing ability to use it even for very sick patients could conceivably increase the role of MRI in the diagnosis of splenic injury in the future.
Radioisotope scintigraphy was used in the diagnosis of splenic injury in the past. Most of the use of radioisotope scintigraphy occurred before the advent of widespread availability of CT scanning, and it is largely of historical interest at this point. Angiography is another test that has been used historically to diagnose splenic injury, but angiography for the diagnosis of splenic injury has largely been replaced by computerized tomography as described above. Angiography with embolization for bleeding does, however, have an important therapeutic role in the management of splenic injury.
Laparoscopy has been tried as a means of diagnosing splenic injury, but is not a diagnostic improvement over CT scanning in patients with blunt trauma. After penetrating trauma, laparoscopy often misses associated bowel injuries. It may have some usefulness in diagnosis and treatment of injuries adjacent to the left hemidiaphragm (see Chapter 28).
GRADING SYSTEMS FOR SPLENIC INJURY
A number of different grading systems have been devised to quantify the degree of injury in patients with ruptured spleens.24–27 These systems have been created based on both the computed tomographic appearance of ruptured spleens and 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) (Fig. 30-5; Table 30-1).24 As with all of the AAST grading systems except that used for hepatic injuries, it uses a scale of between I and V.
TABLE 30-1 The Splenic Organ in Jury Scaling System of the American Association for the Surgery of Trauma, 1994 Revision
FIGURE 30-5 Diagrammatic representation of the splenic organ injury scaling system of the American Association for the Surgery of Trauma. (Reproduced with permission from Carrico CJ, Thal ER, Weigelt JA, eds. Operative Trauma Management: An Atlas. Norwalk, CT: Appleton & Lange; 1998. Copyright The McGraw-Hill Companies, Inc.)
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