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Myelofibrosis, one of the myeloproliferative diseases, is the gradual replacement of the bone marrow by connective tissue. Its main feature is "extramedullary hematopoeisis", i.e. the blood-forming cells migrate to other sites in the body, e.g. the liver or spleen. Typically affects patients > 50 years. Patients will typically have hepatosplenomegaly, and the blood smear will show "teardrop cells".

Further Reading

For more information, see:

  • Myeloproliferative Disease Support List
  • Association of Cancer Online Resource (ACOR) Myeloproliferative Disorders page

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From Gale Encyclopedia of Medicine, 4/6/01 by Teresa G. Norris


Splenectomy is the surgical removal of the spleen, which is an organ that is part of the lymphatic system. The spleen is a dark-purple, bean-shaped organ located in the upper left side of the abdomen, just behind the bottom of the rib cage. In adults, the spleen is about 4.8 × 2.8 × 1.6 in in size, and weighs about 4 or 5 oz. Its functions include a role in the immune system; filtering foreign substances from the blood; removing worn-out blood cells from the blood; regulating blood flow to the liver; and sometimes storing blood cells. The storage of blood cells is called sequestration. In healthy adults, about 30% of blood platelets are sequestered in the spleen.


Splenectomies are performed for a variety of different reasons and with different degrees of urgency. Most splenectomies are done after the patient has been diagnosed with hypersplenism. Hypersplenism is not a specific disease but a group of symptoms, or syndrome, that can be produced by a number of different disorders. It is characterized by enlargement of the spleen (splenomegaly), defects in the blood cells, and an abnormally high turnover of blood cells. It is almost always associated with splenomegaly caused by specific disorders such as cirrhosis of the liver or certain cancers. The decision to perform a splenectomy depends on the severity and prognosis of the disease that is causing the hypersplenism.

Splenectomy always necessary

There are two diseases for which splenectomy is the only treatment--primary cancers of the spleen and a blood disorder called hereditary spherocytosis (HS). In HS, the absence of a specific protein in the red blood cell membrane leads to the formation of relatively fragile cells that are easily damaged when they pass through the spleen. The cell destruction does not occur elsewhere in the body and ends when the spleen is removed. HS can appear at any age, even in newborns, although doctors prefer to put off removing the spleen until the child is five or six years old.

Splenectomy usually necessary

There are some disorders in which splenectomy is usually recommended. They include:

  • Immune (idiopathic) thrombocytopenic purpura (ITP). ITP is a disease involving platelet destruction. Splenectomy is the definitive treatment for this disease and is effective in about 70 percent of chronic ITP cases.
  • Trauma. The spleen can be ruptured by blunt as well as penetrating injuries to the chest or abdomen. Car accidents are the most common cause of blunt traumatic injury to the spleen.
  • Abscesses in the spleen. These are relatively uncommon but have a high mortality rate.
  • Rupture of the splenic artery. Rupture sometimes occurs as a complication of pregnancy.
  • Hereditary elliptocytosis. This is a relatively rare disorder. It is similar to HS in that it is characterized by red blood cells with defective membranes that are destroyed by the spleen.

Splenectomy sometimes necessary

In other disorders, the spleen may or may not be removed.

  • Hodgkin's disease, a serious form of cancer that causes lymph nodes to enlarge. Splenectomy is often performed in order to find out how far the disease has progressed.
  • Thrombotic thrombocytopenic purpura (TTP). TTP is a rare disorder marked by fever, kidney failure, and an abnormal decrease in the number of platelets. Splenectomy is one part of treatment for TTP.
  • Autoimmune hemolytic disorders. These disorders may appear in patients of any age but are most common in patients over 50. The red blood cells are destroyed by antibodies produced by the patient's own body (autoantibodies).
  • Myelofibrosis. Myelofibrosis is a disorder in which bone marrow is replaced by fibrous tissue. It produces severe and painful splenomegaly. Splenectomy does not cure myelofibrosis but may be performed to relieve pain caused by the swollen spleen.
  • Thalassemia. Thalassemia is a hereditary form of anemia that is most common in people of Mediterranean origin. Splenectomy is sometimes performed if the patient's spleen has become painfully enlarged.


Patients should be carefully assessed regarding the need for a splenectomy. Because of the spleen's role in protecting people against infection, it should not be removed unless necessary. The operation is relatively safe for young and middle-aged adults. Older adults, especially those with cardiac or pulmonary disease, are more vulnerable to post-surgical infections. Thromboembolism following splenectomy is another complication for this patient group, which has about 10% mortality following the surgery. Splenectomies are performed in children only when the benefits outweigh the risks.

The most important part of the assessment is the measurement of splenomegaly. The normal spleen cannot be felt when the doctor examines the patient's abdomen. A spleen that is large enough to be felt indicates splenomegaly. In some cases the doctor will hear a dull sound when he or she thumps (percusses) the patient's abdomen near the ribs on the left side. Imaging studies that can be used to demonstrate splenomegaly include ultrasound tests, technetium-99m sulfur colloid imaging, and CT scans. The rate of platelet or red blood cell destruction by the spleen can be measured by tagging blood cells with radioactive chromium or platelets with radioactive indium.


Complete splenectomy

Removal of enlarged spleen

Splenectomy is performed under general anesthesia. The most common technique is used to remove greatly enlarged spleens. After the surgeon makes a cut (incision) in the abdomen, the artery to the spleen is tied to prevent blood loss and reduce the spleen's size. It also helps prevent further sequestration of blood cells. The surgeon detaches the ligaments holding the spleen in place and removes it. In many cases, tissue samples will be sent to a laboratory for analysis.

Removal of ruptured spleen

When the spleen has been ruptured by trauma, the surgeon approaches the organ from its underside and fastens the splenic artery.

Partial splenectomy

In some cases the surgeon removes only part of the spleen. This procedure is considered by some to be a useful compromise that reduces pain from an enlarged spleen while leaving the patient less vulnerable to infection. Long-term follow-up of the results of partial splenectomies has not yet been done.

Laparoscopic splenectomy

Laparoscopic splenectomy, or removal of the spleen through several small incisions, has been more frequently used in recent years. Laparoscopic surgery involves the use of surgical instruments, with the assistance of a tiny camera and video monitor. Laparoscopic procedures reduce the length of hospital stay, the level of post-operative pain, and the risk of infection. They also leave smaller scars. Laparoscopic splenectomy is not, however, the best option for many patients.

Splenic embolization

Splenic embolization is an alternative to splenectomy that is used in some patients who are poor surgical risks. Embolization involves plugging or blocking the splenic artery to shrink the size of the spleen. The substances that are injected during this procedure include polyvinyl alcohol foam, polystyrene, and silicone. Embolization is a technique that needs further study and refinement.


Preoperative preparation for nonemergency splenectomy includes:

  • Correction of abnormalities of blood clotting and the number of red blood cells.
  • Treatment of any infections.
  • Control of immune reactions. Patients are usually given protective vaccinations about a month before surgery. The most common vaccines used are Pneumovax or Pnu-Imune 23 (against pneumococcal infections) and Menomune-A/C/Y/W-135 (against meningococcal infections).


Immediately following surgery, patients should follow instructions and take all medications intended to prevent infection. Blood transfusions may be indicated for some patients to replace defective blood cells. The most important part of aftercare, however, is long-term caution regarding vulnerability to infection. Patients should see their doctor at once if they have a fever or any other sign of infection, and avoid travel to areas where exposure to malaria or similar diseases is likely. Children with splenectomies may be kept on antibiotic therapy until they are 16 years old. All patients can be given a booster dose of pneumococcal vaccine five to 10 years after splenectomy.


The chief risk following splenectomy is overwhelming bacterial infection, or postsplenectomy sepsis. This vulnerability results from the body's decreased ability to clear bacteria from the blood, and lowered levels of a protein in blood plasma that helps to fight viruses (immunoglobulin M). The risk of dying from infection after splenectomy is highest in children, especially in the first two years after surgery. The risk of postsplenectomy sepsis can be reduced by vaccinations before the operation. Some doctors also recommend a two-year course of penicillin following splenectomy or long-term treatment with ampicillin.

Other risks following splenectomy include inflammation of the pancreas and collapse of the lungs. In some cases, splenectomy does not address the underlying causes of splenomegaly or other conditions. Excessive bleeding after the operation is an additional possible complication, particularly for ITP patients. Infection immediately following surgery may also occur.

Normal results

Results depend on the reason for the operation. In blood disorders, the splenectomy will remove the cause of the blood cell destruction. Normal results for patients with an enlarged spleen are relief of pain and of the complications of splenomegaly. It is not always possible, however, to predict which patients will respond well or to what degree.

Key Terms

An alternative to splenectomy that involves injecting silicone or similar substances into the splenic artery to shrink the size of the spleen.
Hereditary spherocytosis (HS)
A blood disorder in which the red blood cells are relatively fragile and are damaged or destroyed when they pass through the spleen. Splenectomy is the only treatment for HS.
A syndrome marked by enlargement of the spleen, defects in one or more types of blood cells, and a high turnover of blood cells.
Immune or idiopathic thrombocytopenic purpura (ITP)
A blood disease that results in destruction of platelets, which are blood cells involved in clotting.
An instrument used to view the abdominal cavity through a small incision and perform surgery on a small area, such as the spleen.
A vaccine that is given to splenectomy patients to protect them against bacterial infections. Other vaccines include Pnu-Imune and Menomune.
A generalized infection of the body, most often caused by bacteria.
A process in which the spleen withdraws some normal blood cells from circulation and holds them in case the body needs extra blood in an emergency. In hypersplenism, the spleen sequesters too many blood cells.
Abnormal enlargement of the spleen.
A clot in the blood that forms and blocks a blood vessel. It can lead to infarction, or death of the surrounding tissue due to lack of blood supply.

Further Reading

For Your Information


  • Hohn, David C., "Spleen." In Current Surgical Diagnosis & Treatment, edited by Lawrence W. Way, Stamford, CT: Appleton & Lange, 1994.
  • Packman, Charles H., "Autoimmune Hemolytic Anemia." In Conn's Current Therapy, edited by Robert E. Rakel, Philadelphia: W. B. Saunders Company, 1998.
  • Tanaka, Kouichi R., "Nonimmune Hemolytic Anemia." In Conn's Current Therapy, edited by Robert E. Rakel, Philadelphia: W. B. Saunders Company, 1998.


  • Tsoukas, Christos M., et al. "Effect of Splenectomy on Slowing Human Immunodeficiency Virus Disease Progression." Archives of Surgery 133 (January 1998): 25- 31.


  • National Heart, Lung and Blood Institute. Building 31, Room 4A21, Bethesda, MD 20892. (301)496-4236.
  • Leukaemia Research Fund. 43 Great Ormond St., London WCIN 3JJ.


  • Foxhall Surgical Home Page.
  • Non-emergency Surgery Hotline. (800) 638-6833.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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