Chapter 22

Spleen

R. Anthony Carabasi III

John C. Kairys

John S. Radomski

I Introduction

A Anatomy

Developmental considerations

The spleen develops from mesenchymal tissue in the dorsal mesogastrium. This tissue rotates to the left as development progresses. By the end of the third gestational month, the organ is formed. The point at which the spleen remains attached to the dorsal mesogastrium becomes the gastrosplenic ligament.

The organ itself consists of an outer capsule and trabeculae, which enclose the pulp. The pulp consists of three zones:

The white pulp is essentially a lymph node. It contains lymphocytes, macrophages, and plasma cells in a reticular network.

The red pulp consists of cords of reticular cells with sinuses in between.

The marginal zone is a poorly defined vascular space between the pulps.

The adult spleen weighs between 100 g and 150 g and measures 12 × 7 × 4 cm.

Location. The spleen is located in the left upper quadrant of the abdomen and is protected by the eighth to the eleventh ribs. It is bordered by the left kidney posteriorly, the diaphragm superiorly, and the fundus of the stomach and the splenic flexure of the colon anteriorly.

Vasculature

The main blood supply is the splenic artery , which is a branch of the celiac axis. It travels along the superior border of the pancreas. At the hilus, it branches into trabecular arteries, which terminate in small vessels to the splenic pulp.

The splenic vein crosses behind or at the lower border of the pancreas. It joins the superior mesenteric vein to form the portal vein (Fig. 22 -1).

B Physiology

The spleen has multiple functions, some of which remain poorly understood. Its most important functions are its ability to act as a blood filter and its role in the immunologic process of the body.

Filtering functions. Splenic blood flow is approximately 350 L/day of blood. Most blood elements pass through rapidly and uneventfully.

Removal of old or abnormal red blood cells

The spleen removes about 20 mL/day of aged or abnormal red blood cells.

Secondary hypersplenism is caused by an identifiable underlying disease, such as:

Disorders of splenic blood flow

Hematopoietic disorders leading to increased red blood cell turnover

Immune disorders

Infiltrative disorders

Infectious diseases

Neoplastic diseases

C Presentation

Anemia, leukopenia, or thrombocytopenia may be noted on a routine laboratory workup.

Anemia may lead to pallor, fatigue, and dyspnea.

Leukopenia may lead to increased susceptibility to infection.

Thrombocytopenia is characterized by easy bruising and epistaxis.

Splenomegaly may be found incidentally during the physical examination or in a radiologic imaging study.

The patient may present with pain secondary to splenic enlargement or rupture.

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D Evaluation

Peripheral blood smears may demonstrate a decreased number of red blood cells, white blood cells, or platelets.

Reticulocytosis is frequently observed if the hypersplenism is causing an increased turnover of red blood cells.

Abnormal red blood cell morphology is sometimes diagnostic for the underlying hematologic disorder (e.g., spherocytosis).

Bone marrow aspirate

A compensatory increase in megakaryocytes should be observed if there is sequestration of platelets in the spleen.

Abnormalities of hematopoiesis may be identified as well.

Radiologic imaging

An ultrasound or a computed tomography (CT) scan can accurately document the size of the spleen as well as determine any structural abnormalities. Other findings on the scans may suggest an underlying disease process.

Radioisotope scans may demonstrate a shortened half -life for circulating blood elements and their sequestration in the spleen.

Immunologic tests using specific antibodies may be diagnostic for certain diseases, particularly those with an autoimmune basis.

E

Treatment depends on the underlying condition. Table 22 -1 summarizes the role of surgery in various pathologic conditions.

TABLE 22-1 Absolute and Relative Indications for Splenectomy

Spontaneous rupture

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III Pathologic Conditions Affecting the Spleen

A Primary splenic disorders

Primary hypersplenism is essentially a diagnosis of exclusion; it is made only after possible causes of secondary hypersplenism have been ruled out.

It is rare, and it affects mainly women.

There is an exaggerated destruction or sequestration of circulating blood elements.

Any one or all of the formed blood elements may be involved.

The hematologic findings may be accompanied by recurrent fevers and infections.

Splenomegaly is almost always present.

It may, in some cases, actually be an early manifestation of lymphoma or leukemia.

The treatment is splenectomy. Steroids do not improve the condition.

Splenic cysts may be idiopathic or, more commonly, may result from previous trauma. Surgery is indicated if the cysts become large enough to cause pain or torsion or if they exert a significant mass effect on surrounding structures. With simple cysts, unroofing is sufficient, thus preserving splenic function.

B Disorders of splenic blood flow

Portal hypertension may cause passive splenic congestion.

It is the most common mechanism of secondary hypersplenism.

Causes of portal hypertension include alcoholic cirrhosis, viral hepatitis, Budd -Chiari syndrome, and congestive heart failure.

Hypersplenism associated with portal hypertension is usually mild and clinically insignificant. Only 15% of patients develop significant hypersplenism; therefore, isolated splenectomy is generally not indicated.

Splenic vein thrombosis can cause secondary hypersplenism with massive splenomegaly.

Cause. Pancreatitis is the usual cause of the thrombosis.

Presentation. The patient may present with bleeding from esophageal or, more characteristically, proximal gastric varices.

Treatment. The hypersplenism and bleeding varices are cured by splenectomy.

Splenic artery aneurysm (see Chapter 7)

C Hematopoietic disorders

Hereditary spherocytosis is one of a group of hereditary hemolytic anemias that cause the most severe symptoms.

Characteristics

Hereditary spherocytosis is characterized by a defect of the red blood cell membrane that results in loss of red blood cell surface area, which causes the cell to be spherical (hence the name), small, and more susceptible to lysis than normal red blood cells.

The cell membrane is thick and rigid, which causes the cells to be held in the splenic pulp. This holding of cells leads to cell lysis, due to deprivation of glucose and adenosine triphosphate (ATP), and occurs only in the spleen.

It is transmitted as an autosomal dominant trait.

Symptoms

Symptoms of hereditary spherocytosis include malaise, abdominal discomfort, jaundice, anemia, and splenomegaly.

The disease may be complicated by gallstones (which are rare in patients younger than 10 years of age) and by chronic leg ulcers that heal only after splenectomy.

Diagnosis is based on the preceding clinical findings and the results of laboratory studies, which include a demonstration of the following:

Spherocytes and an elevated reticulocyte count on a Wright-stained blood smear

Increased osmotic fragility of the red blood cells

Chromium 51 (51 Cr)-tagged red blood cells, which have a greatly shortened half -life and are sequestered in the spleen

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Treatment is splenectomy.

This procedure cures the anemia and jaundice in all patients. Failure of splenectomy to cure the patient is normally caused by an accessory spleen that has been overlooked during the operation.

The operation should be delayed until 4 years of age, if possible, to decrease the chance of postsplenectomy sepsis (see V F 1).

The gallbladder should be removed at the time of splenectomy if gallstones are present.

Other congenital hemolytic anemias. Although splenectomy is not curative, it is indicated occasionally because it reduces the need for multiple transfusions in the following conditions:

Enzyme deficiencies, such as glucose -6-phosphate dehydrogenase (G6PD) deficiency and pyruvate kinase deficiency

Hereditary elliptocytosis, in which most of the patient's erythrocytes are misshapen (i.e., they are elliptical) and there are varying degrees of anemia and red blood cell destruction

Thalassemia major, which is transmitted as a dominant trait and is characterized by defective hemoglobin synthesis that causes homozygotes to have severe anemia and hepatosplenomegaly

Sickle cell anemia

Most patients with sickle cell anemia “autosplenectomize” because of multiple infarcts caused by stagnation and stasis of the abnormal red blood cells.

These patients may require splenectomy in rare cases in which excessive splenic sequestration of red blood cells is documented or when areas of infarction develop an abscess.

Congenital erythropoietic porphyria is a rare autosomal recessive defect of pyrrole metabolism that leads to deposition of porphyrins in the skin and other tissues.

Patients have photosensitivity, bullous dermatitis, and hemolytic anemia.

Splenectomy improves the hemolytic anemia and decreases tissue levels of porphyrins.

D Immune disorders

Idiopathic autoimmune hemolytic anemia occurs most commonly in persons older than 50 years of age and occurs twice as often in women than in men.

Clinical presentation

In this disorder, both warm and cold hemolytic antibodies have been described. These antibodies presumably shorten the life of the red blood cells.

The anemia is accompanied by reticulocytosis. There is splenomegaly in 50% of the patients, and there may be mild jaundice.

Diagnosis. The direct Coombs' test result is positive. 51 Cr-tagged red blood cells may demonstrate sequestration in the spleen.

Treatment. The disease may run a self-limited course that requires no treatment.

Steroids and azathioprine are administered in more persistent cases.

Splenectomy is helpful in some patients, especially if they have demonstrated excessive

splenic sequestration of 51 Cr-tagged red blood cells, and if steroids are ineffective or contraindicated.

Idiopathic thrombocytopenic purpura (ITP)

The etiology is unknown but is presumed to be immunologic because most patients with chronic disease have platelet-agglutinating antibodies that rapidly destroy transfused platelets.

The acute form is more common in children younger than 16 years. Eighty percent of affected individuals recover spontaneously.

Diagnosis should be suspected if signs of abscess, such as fever and an elevated white blood cell count, occur in association with left upper quadrant fullness or tenderness. It can be confirmed by CT scan and scanning with technetium-99m (99m Tc).

Treatment is broad spectrum antibiotics and splenectomy. Percutaneous drainage may be considered in select cases, but hemorrhage is a potential complication.

Viral infections including mononucleosis, human immunodeficiency virus, and hepatitis may cause transient splenomegaly and hypersplenism.

Parasitic infections including malaria, leishmaniasis, or trypanosomiasis affect blood cells and may cause splenomegaly. An echinococcal cyst may develop in the spleen. Partial or total splenectomy is curative.

Fungal infection with histoplasmosis produces characteristic areas of calcification within the spleen.

G Neoplastic diseases

Primary splenic tumors are rare.

They include lymphoma, sarcoma, hemangioma, and hamartoma.

Symptoms are caused by the enlarged spleen, and there may be associated hypersplenism.

Treatment is splenectomy.

Metastatic disease from solid tumors is uncommon, probably owing to its efficient immune mechanism.

Hodgkin's disease. Advances in therapy have greatly improved chances for the cure or long-term survival of patients with this disease. Treatment may include radiation therapy alone, chemotherapy alone, or a combination of both.

Types of staging (see Chapter 19)

Staging laparotomy consists of liver biopsy, splenectomy, complete abdominal exploration, and sampling of lymph nodes from multiple areas but is now performed only rarely.

Indications for staging laparotomy in patients with Hodgkin's disease are changing.

Traditionally, patients with clinical stage I or II disease and sometimes stage IIIA disease were considered for staging laparotomy.

Studies suggest that laparotomy may not be needed for many patients.

Current imaging techniques have improved diagnostic accuracy.

Oncologists are now treating more stages of Hodgkin's disease with chemotherapy alone or in combination with radiation therapy, thus obviating laparotomy.

There is no evidence that splenectomy improves the survival rate.

There appears to be an increased risk of secondary leukemias in patients who have undergone staging laparotomy and splenectomy.

There is a risk of morbidity and mortality with laparotomy.

Laparotomy is clearly not indicated in patients with stage IIIB or IV disease.

Chemotherapy is the treatment of choice.

Non -Hodgkin's lymphoma

Staging for non -Hodgkin's lymphoma uses the same classification as for Hodgkin's disease. Careful evaluation reveals stage III or IV disease in most patients.

Laparotomy is not frequently used in non -Hodgkin's lymphoma. Percutaneous liver biopsy, laparoscopy, or bone marrow biopsy frequently reveals diffuse disease.

Splenectomy may be useful in some of these patients to treat hypersplenism or to relieve symptoms of massive splenomegaly.

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Leukemias

Patients with chronic lymphocytic leukemia (CLL) or chronic myelogenous leukemia (CML) may develop thrombocytopenia and massive splenomegaly. Splenectomy is indicated for symptomatic relief.

Patients with hairy cell leukemia and hypersplenism may benefit from splenectomy.

H Miscellaneous lesions

Rupture of the spleen may follow either penetrating or nonpenetrating trauma as well as iatrogenic injury, or rupture may occur spontaneously.

Traumatic rupture (see Chapter 21 I C 7e–8b )

Iatrogenic (intraoperative) trauma accounts for 20% of all splenectomies. The trauma results from excessive traction on the splenic attachments or from misplacement of retractors.

Spontaneous rupture usually occurs because of massive splenomegaly due to an associated disease.

Splenosis is autotransplantation of splenic fragments throughout the abdominal cavity.

Autotransplantation has been attempted to preserve splenic immunologic function following splenectomy for trauma. No benefit has ever been proved.

Splenosis may occur spontaneously after rupture of the spleen. When splenectomy is being performed for disease, splenosis may lead to resumption of the hypersplenic state.

Aneurysms of the splenic artery (see Chapter 7)

Ectopic and accessory spleens

The tail of the pancreas may be injured during attempts to secure hemostasis of the splenic pedicle. This injury may result in postoperative pancreatitis, abscess, or phlegmon formation.

C

Postoperative hemorrhage may result from inadequate hemostasis of the splenic pedicle or the short gastric vessels.

D

Subphrenic abscess may develop and is usually accompanied by a left pleural effusion.

E

Thrombocytosis postoperatively is common. If the platelet count exceeds 1 million, anticoagulation may be required to prevent spontaneous thrombosis.

F Postsplenectomy sepsis

Overview. Some patients are susceptible to overwhelming sepsis following splenectomy. The syndrome begins with nonspecific, mild, influenzalike symptoms and progresses to high fever, shock, and death.

In general, the younger the patient and the more serious the disease requiring the splenectomy, the greater is the risk for the development of overwhelming sepsis. The risk is greatest if splenectomy occurs during the first 2–4 years of life, particularly if it is done for a disease of the reticuloenclothelial system.

In healthy adults who have the spleen removed for trauma, the incidence of overwhelming sepsis is low (<0.5%), but it is still higher than that in the normal population (0.01%).

Approximately 80% of septic episodes occur within 2 years after splenectomy.

d. Typically, the causitive organisms are encapsulated bacteria, including Streptococcus pneumoniae ,

Neisseria meningitidis , and Haemophilus influenzae.

Prevention and treatment

Polyvalent pneumococcal vaccine should be given to all splenectomized patients, which will protect them from 80% of pathogenic pneumococci (the organisms that most commonly cause the sepsis).

Vaccines for N. meningitidis and H. influenza e should be administered as well.

Prophylactic penicillin may be given to high-risk pediatric patients.

Patients should be instructed to seek medical attention immediately if symptoms begin, and penicillin therapy should be started in an attempt to prevent the full -blown syndrome from developing.

VI Critical Points

The spleen is an important but not essential organ that has a role in filtering and sequestering circulating blood elements.

The spleen has an important immunologic role, filtering opsonized bacteria from the circulation and providing a site for antibody synthesis.

Hypersplenism should not be confused with splenomegaly.

Hypersplenism refers to the exaggerated destruction of sequestration of circulating red blood cells, white blood cells, or platelets.

Splenomegaly refers to physical enlargement of the spleen only.

Primary hypersplenism is uncommon and is a diagnosis of exclusion, occurring mostly in women.

Most cases of hypersplenism are secondary to other pathologic conditions.

Disorders of splenic blood flow, including portal hypertension or splenic vein thrombosis

Hematopoietic disorders, including hereditary spherocytosis, hemolytic anemias, sickle cell disease, or congenital erythropoietic porphyria

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Immunologic disorders, including idiopathic autoimmune hemolytic anemia, ITP, TTP, or Felty's syndrome.

ITP is one of the most common reasons for elective splenectomy. In this condition, the spleen is generally normal in size.

Infiltrative diseases, including myeloid metaplasia, sarcoidosis, or Gaucher's disease

Infection diseases, including bacterial, viral, parasitic, or fungal infections

S. aureus and streptococci are the most common etiologic agents.

Neoplastic diseases of the spleen are uncommon but may include primary tumors, metastatic tumors, or hematologic disorders such as lymphoma. Staging laparotomies are now uncommonly performed.

Traumatic rupture of the spleen can often be managed nonoperatively. Splenectomy is reserved for those patients who are unstable or who have additional, massive injuries.

The management of most cases of hypersplenism is medical. Splenectomy usually has only a secondary role, when symptoms are significant or medical therapy fails to control the disease.

The conditions where surgery is clearly indicated are bleeding esophagogastric varices associated with splenic vein thrombosis, hereditary spherocytosis, splenic abscess, echinococcal cyst, primary splenic tumors, massive splenic trauma, or spontaneous rupture (Table 22 -1).

Surgery is frequently performed through a laparotomy incision but may also be performed laparoscopically , when the skill of the surgeon and the size of the spleen permit.

Patients undergoing splenectomy are at risk for developing overwhelming postsplenectomy sepsis. This risk is greatest in young children. The risk can be decreased by prophylactically immunizing patients preoperatively or postoperatively, if necessary.