The spleen is a lymphatic organ located in the left upper abdominal quadrant. It contains the largest accumulation of lymphoid cells in the body. In addition to filtering the blood, it plays an important role in host defense. Splenic lymphocytes are involved in antigen recognition and plasma cell production, whereas splenic endothelial macrophages extract bacteria and damaged red blood cells from circulation by phagocytosis. White pulp of the spleen contains high concentrations of antigen-presenting cells and receives arterial blood supply first. Blood then travels through an open-type circulation known as the red pulp, where foreign particles are filtered and antibody-coated cells are removed. Removal of red blood cell imperfections is another function of the spleen. These include Howell-Jolly bodies (Fig 8-1), which are nuclear remnants, Pappenheimer bodies, which are iron inclusions, and Heinz bodies, which are denatured hemoglobin. Splenectomy or hyposplenism is associated with the presence of these abnormalities in the peripheral blood.
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Figure 8-1 • Howell-Jolly bodies. These are round nuclear fragments that are chromosomes separated from the mitotic spindle during abnormal mitosis. From Anderson SC. Anderson's Atlas of Hematology. Philadelphia: Lippincott Williams & Wilkins, 2003. |
Surgical issues regarding the spleen are multiple and varied. Life-threatening hemorrhage from a lacerated spleen resulting from trauma is a common problem, requiring swift surgical intervention. Certain disease states, such as immune thrombocytopenic purpura (ITP) and the hemolytic anemias, are often treated with splenectomy when medical management fails. Splenectomy may be necessary as part of another operation, such as distal pancreatectomy. In addition, the traditional staging workup for Hodgkin disease has involved removal of the spleen to determine extent of disease, although this is now rarely performed.
ANATOMY
The spleen is embryologically derived from condensations of mesoderm in the dorsal mesogastrium of the developing gastrointestinal tract. In the mature abdomen, the spleen is found attached to the stomach by the gastrosplenic ligament and to the left kidney by the splenorenal ligament. Other supporting attachments include the splenocolic and splenophrenic ligaments (Fig. 8-2).
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Figure 8-2 • Normal anatomic relations of the spleen. The spleen lies behind the stomach and above the left kidney. It is an intra-abdominal organ, although its blood supply courses through the retroperitoneum. |
Accessory spleens are present in approximately 25% of patients. They are most often found in the splenic hilum and in the supporting splenic ligaments and greater omentum.
Arterial blood is mostly supplied via the splenic artery, which is one of three branches of the celiac axis (splenic, left gastric, common hepatic). At the hilum, the splenic artery divides into smaller branches that supply the several splenic segments. Additional arterial blood is supplied via the short gastric and left gastroepiploic vessels (Fig. 8-3).
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Figure 8-3 • Arterial supply of the spleen. |
Venous drainage is from segmental veins that join at the splenic hilum to form the splenic vein. Running behind the upper edge of the pancreas, the splenic vein joins with the superior mesenteric vein to form the portal vein.
SPLENIC HEMORRHAGE
The most common cause of splenic hemorrhage is blunt abdominal trauma. Nonpenetrating injury may cause disruption of the splenic capsule or frank laceration of the splenic parenchyma. Displaced rib fractures
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of the left lower chest often cause splenic laceration. Splenic injuries are graded from I to V based on the extent of laceration and hematoma (Table 8-1).
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TABLE 8-1 Grades of Splenic Injury |
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Splenic hemorrhage may also be iatrogenic. Intraoperative damage to the spleen may occur during unrelated abdominal surgery that results in bleeding controlled only by splenectomy. Estimates are that 20% of splenectomies result from iatrogenic causes. Infectious diseases (e.g., mononucleosis, malaria) may damage the spleen to the point that unnoticed blunt trauma can cause "spontaneous" splenic rupture and hemorrhage.
HISTORY
Patients typically present with a recent history of trauma, usually to the left upper abdomen or left flank.
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PHYSICAL EXAMINATION
Depending on the degree of splenic injury and hemo-peritoneum, a physical examination may reveal left upper quadrant abdominal tenderness, left lower rib fractures, abdominal distention, peritonitis, and hypovolemic shock. Pain on the left shoulder is referred to as Kerr's sign and is referred pain from peritoneal irritation.
DIAGNOSTIC EVALUATION
Computed tomography (CT) scan, abdominal ultrasound, and peritoneal lavage (see Chapter 27, Trauma) can be used to detect intraperitoneal blood. In hemodynamically stable patients, CT can demonstrate the degree of both splenic injury and hemoperitoneum.
TREATMENT
For patients with splenic injury who are hemodynamically stable and without evidence of ongoing hemorrhage, nonoperative management with close hemodynamic monitoring has become the accepted treatment of choice. In children, nonoperative management is widely applied as a result of the incidence of overwhelming postsplenectomy sepsis seen in the pediatric population. Recent advances in interventional radiology have made it possible to embolize the spleen, or a portion, to obviate the need for laparotomy. This can have the advantage of salvaging enough of the spleen to prevent major complications, such as postsplenectomy sepsis, but splenic abscess may occur. For patients with known or suspected splenic injury who are hemodynamically unstable, operative intervention is indicated to control ongoing hemorrhage.
Once in the operating room, the decision to perform splenic repair (splenorrhaphy) versus splenectomy is based on the degree of injury to the par-enchyma and blood supply of the organ. Relatively minor injuries, such as a small capsular laceration with minor oozing, may be repaired, whereas a fragmented spleen with involvement of the hilar vessels necessitates surgical removal. If splenic repair is contemplated, the spleen must be mobilized completely to determine the extent of injury and the likelihood of success. If there are other organs injured in addition to the spleen, splenectomy is generally recommended.
IMMUNE THROMBOCYTOPENIC PURPURA
ITP is an autoimmune hematologic disease in which antiplatelet IgG antibodies, produced largely in the spleen, are directed against a platelet-associated antigen, resulting in platelet destruction by the reticuloendothelial system and subsequent thrombocytopenia. The disease is typically seen in young women, who may present with complaints of menorrhagia, easy bruising, mucosal bleeding, and petechiae. Men may present with complaints of prolonged bleeding after shaving trauma.
TREATMENT
Initial therapy is with corticosteroids, which improve platelet counts after 3 to 7 days of therapy. Initial doses are 1 mg/kg orally until the platelet count is normal, followed by a 4- to 6-week taper. High-dose dexamethasone or methylprednisolone is also an option. Intravenous immunoglobulin can be used to support the platelet count, as can anti-Rh(D) if patients have Rh(D) positive platelets. For prolonged active bleeding, platelet transfusions should be administered to achieve hemostasis. If patients are asymptomatic, platelet counts of <30,000 can be tolerated. Once patients become symptomatic or the platelet count decreases to <10,000, therapy should be considered. Patients with chronic refractory ITP may benefit from rituximab or thrombopoiesis-stimulating agents, but these are considered experimental at this time.
Few patients enjoy complete and sustained remission with corticosteroid treatment alone. Patients typically become refractory to medical treatment, and thrombocytopenia recurs. Splenectomy is then indicated. After splenectomy, normal platelet counts develop in approximately 80% of patients because the organ of both significant antiplatelet antibody production and platelet destruction is removed.
HYPERSPLENISM
Hypersplenism describes a state of increased splenic function that results in various hematologic abnormalities, which can be normalized by splenectomy. Elevated splenic function causes a depression of the formed blood elements, leading to a compensatory hyperplasia of the bone marrow.
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HISTORY
As in ITP, most patients are women who present with signs of anemia, recurrent infections, or easy bruising.
PHYSICAL EXAMINATION
Abdominal examination reveals splenomegaly.
DIAGNOSTIC EVALUATION
Peripheral-blood smear may reveal leukopenia, anemia, thrombocytopenia, or pancytopenia. Bone marrow biopsy shows pancellular hyperplasia.
TREATMENT
Splenectomy may produce hematologic improvement.
HEMOLYTIC ANEMIAS
Hemolytic anemias are characterized by an elevated rate of red blood cell destruction from either a congenital or acquired etiology. Congenital hemolytic anemias result from basic defects of the cell membrane (hereditary spherocytosis), hemoglobin synthesis (thalassemia), hemoglobin structure (sickle cell anemia), or cellular metabolism (glucose-6-phosphate dehydrogenase deficiency). Acquired autoimmune hemolytic anemias result when antibodies are produced that are directed against the body's own red blood cells.
DIAGNOSTIC EVALUATION
A positive direct Coombs test demonstrates complexed antibodies on the red blood cell membrane. Warm-reactive antibodies are IgG, and cold-reactive antibodies are IgM.
TREATMENT
The role of splenectomy in treating hemolytic anemias depends on the particular disease process. For example, red blood cell survival normalizes after splenectomy for hereditary spherocytosis, whereas operative intervention has no role in the treatment of anemia of glucose-6-phosphate dehydrogenase deficiency that is secondary to a defect of metabolism, not cellular structure. Occasionally, splenectomy may be useful in selected patients with sickle cell anemia and thalassemia. Patients with autoimmune hemolytic anemias undergo initial corticosteroid treatment and progress to splenectomy only after medical treatment failure.
HODGKIN DISEASE STAGING
Because of a greater reliance on CT scans and the favorable success of salvage chemotherapy in the treatment of Hodgkin lymphoma, the need for determining whether disease is present across the diaphragm by means of laparotomy and splenectomy has sharply declined. Treatment with salvage chemotherapy after local radiation failure still carries a highly favorable outcome in most cases. Therefore, splenectomy for staging Hodgkin disease is now rarely performed.
OVERWHELMING POSTSPLENECTOMY SEPSIS
Asplenic individuals are at greater risk for developing fulminant bacteremia because of decreased opsonic activity, decreased levels of IgM, and decreased clearance of bacteria from the blood after splenectomy. As a rule, children are at greater risk for development of sepsis than are adults, and fatal sepsis is more common after splenectomy for hematologic disorders than after trauma. The risk of sepsis is higher in the first postoperative year, and, for adults, each subsequent year carries approximately a 1% chance of developing sepsis. Other data show a mortality of less than one per 1,000 patient-years. The clinical picture of overwhelming postsplenectomy sepsis is the onset of high fever followed by circulatory collapse from septic shock. Disseminated intravascular coagulation often occurs. The offending pathogens are the encapsulated bacteria Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis.
Splenectomy Considerations
Any patient scheduled to undergo splenectomy should receive immunization against Steptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, preferably at least 2 weeks before surgery. Straightforward splenectomy can be performed laparoscopically, whereas complicated splenectomy in patients with massive spleens or severe thrombocytopenia are more likely to require laparotomy. During surgery, the spleen is mobilized from the splenorenal, phrenosplenic, and lienocolic ligaments. The main artery is found on the superior border of the pancreas and should generally
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be taken early. Care must be taken to control the short gastric arteries entering the greater curve of the stomach. The tail of the pancreas nestles into the splenic hilum and can be damaged, causing a pancreatic leak or fistula. Patients generally have nasogastric decompression to prevent the stomach from distending and hemorrhage along the greater curve. Patients with compromised immune systems, including young children and transplant recipients, should be considered for long-term oral penicillin prophylaxis.
SPLENIC ABSCESS
Splenic abscesses most commonly occur as a consequence of other intra-abdominal infection. They can also occur after arterial embolization of either the liver or spleen. Diabetes seems to be a risk factor. Patients generally present with left upper quadrant pain, fever, and leucocytosis. Antibiotics, catheter-based drainage, and splenectomy are all appropriate management options.
KEY POINTS