Splenomegaly
and HypersplenismIntroduction: The spleen contains
two different parts that look and function differently, the white pulp and the
red pulp. The white pulp which is located more in the periphery of arteries is
an immune organ consisting of lymphatic tissue. The
red pulp is lining the sinuses and cords (part of the venous system within the
spleen) and is filled with macrophages and granulocytes whose function is to remove
old and damaged red blood cells and old platelets (thrombocytes). The white pulp
functions as an immune organ producing B cells and T cells. The B cells produce
antibodies against viruses such as the flu etc. However in the case of immune
hemolytic anemias with a positive Coombs’ test these B cells will produce autoantibodies
directed against blood cells. The red pulp will remove antibody coated red blood
cells and old and defective red blood cells. This includes inclusion bodies like
Heinz bodies (globin that is insoluble) and Howell-Jolly bodies (nuclear fragments).
When the spleen is not functioning because of fibrotic changes or when a splenectomy
has been performed in the past, the hematologist will be able to tell this from
a stained blood smear where Heinz bodies and Howell-Jolly bodies will be present.
Splenomegaly simply means “large spleen”. This can be caused by a large number
of unrelated medical conditions. Congestive disease can be found with end stage
cirrhosis (Banti’s disease). Myeloproliferative diseases such as Hodgkin’s
disease, leukemia, primary thrombocythemia and polycythemia vera can all develop
splenomegaly as part of their illness. Infectious diseases (particularly infectious
mononucleosis, bacterial endocarditis, hepatitis and psittacosis, but also tuberculosis,
brucellosis, malaria and syphilis etc.) and inflammatory diseases (like sarcoidosis,
lupus or Felty’s syndrome) are known causes of splenomegaly as well. Congenital
forms of anemias and hemolytic anemias often have splenomegaly as part of the
clinical presentation. Finally, the lipoid storage diseases (Gaucher’s, Hand-Schüller-Christian,
Niemann-Pick diseases etc.) and the nonlipoid storage diseases (Letterer-Siwe
disease etc.) as well as amyloidosis can all cause splenomegaly. Hypersplenism:
Once splenomegaly is present, it does not seem to matter much what the
underlying cause for the enlarged spleen was, but the spleen is now much more
effective in filtering out red blood cells, white blood cells and platelets. Whatever
cell line is removed, the bone marrow will increase production so that the loss
of the cell line is compensated for (compensatory bone marrow hyperplasia). This
can mask the symptoms somewhat and delay the diagnosis. Eventually though the
bone marrow cannot keep up the cell production and there will be anemia (when
the red blood cells are affected), leucopenia (white blood cells diminished) or
thrombocytopenia (platelets affected). In summary, hypersplenism is present when
there is a reduction of a line of blood cells as the result of splenomegaly. Symptoms: The
symptoms are from the underlying disease process. In addition there can be a feeling
of satiety early into a meal from the pressure of the enlarged spleen on the neighboring
stomach. The larger the spleen, the more fullness the patient feels even between
meals. In addition there may be pain in the left upper abdomen. Infarcts can form
within the spleen and this would be associated with severe left upper abdominal
pain and may be mistaken first for a heart attack. If there are recurrent infections
and anemia the physician often will feel for the spleen and detect the enlargement.
However, studies have shown that even with the best physical examination the doctors
will only pick up about 65% of the otherwise proven splenomegaly. Percussion will
detect about 70% of otherwise proven splenomegaly. This simply means that physical
examination has a sensitivity for detection of only 65 to 70%. Diagnostic
tests: Ultrasound examination is the method of choice as it detects
100% and also shows details of the infrastructure of the enlarged spleen (high
accuracy, low cost). However, in certain cases the hematologist may want to order
an MRI scan, if more details are required (clots in the portal or splenic veins).
In the past nuclear scans were also performed, but this has been replaced by CT
and MRI scans. Causes of the underlying illness have to be worked up with specific
tests that the hematologist will choose depending on the history and the clinical
findings in a particular patient. To avoid later complications a particular effort
must be made to rule out an underlying or occult infection. Repeat CBC (complete
blood count) tests and blood cultures should be ordered. The hematologist should
also examine bone marrow samples. Blood smears, liver function tests and lymphoma
screening tests (flow cytometry) are only some of the baseline tests that likely
will be performed. For detection of lymphoproliferative disorders serum protein
electrophoresis would be ordered. A diffuse hypergammaglobulinemia would indicate
a chronic infection like tuberculosis, malaria, kalazar or brucellosis. Treatment: Splenomegaly is merely
a symptom of these other diseases that are mentioned above. Treatment is therefore
directed against the underlying conditions. Splenomegaly by itself is not a threat
to the patient unless there is hypersplenism present as well. If severe hypersplenism
(see above) is present a hematologist needs to be consulted on an urgent basis
as a decision may have to be made soon whether or not a splenectomy is needed.
There is a correlation between the spleen size and the degree of the anemia. It
is a difficult decision to decide when to do a splenectomy and when to keep the
spleen. The spleen is a major immune organ, so removing it will weaken the immune
system and be a potential risk in future to the patient. On the other hand there
are conditions that are known risks and if the spleen is not taken out the patient
would likely die. For instance, in Gaucher’s disease, which is a lipid storage
disease, the spleen can turn 30 times the normal size and be life threatening
as it causes a severe lowering of all blood cell types (called a “pancytopenia).
The spleen can be removed surgically or can be radiated to “ablate” it. This
renders it non functional by inducing radiation fibrosis and the blood cells can
recover by either of these two treatments. The hematologist has the necessary
experience that it takes in these difficult situations to know which way to go.
Hereditary spherocytosis and thalassemia are two other conditions where hypersplenism
can set in with a splenomegaly. Again a decision needs to be made early enough
and based on a thorough investigation and assessment by a hematologist whether
or not a splenectomy or radiation therapy would be beneficial to the patient.
Whenever possible a splenectomy should be avoided as the spleen’s normal function
is to protect the body against bacteria that are encapsulated. Patients who had
a splenectomy need to be protected against these bacteria by a vaccination program.
Pneumococcal vaccine, meningococcal vaccine and vaccination against Haemophilus
influenzae are routinely given. This will prevent pneumococcal pneumonia, bacterial
meningitis and H.influenzae pneumonia. The patient is also more prone to septicemia,
which is a life threatening condition with free floating bacteria in the blood.
Empiric antibiotic prophylaxis is given before high risk procedures are done like
dental work, gynecological procedures, prostatic surgery, cystoscopy, bronchoscopy,
bile duct surgery or procedures (ERCP), etc. |
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