In Spleen 2 we saw that the circulation of the spleen was so designed that it acts as a filter to stop damaged red cells from continuing to circulate. Red cells last for 120 days and then they run out of energy and can't maintain their structure. The dying red cells can't escape the Cords of Bilroth and get eaten by macrophages.
Platelets live for much shorter periods - around 9 days, but they die, not from old age, but by being used as plugs in the holes in capillaries. Antibody coated platelets (as in ITP) just like antibody coated red cells (as in AIHA) also get trapped in the Cords of Bilroth,
But in this section I want to talk about the lymphocytes. Remember, they were skimmmed off in the penicillate arteries with the plasma, and this then enters the white pulp of the spleen. The white pulp of the spleen is the largest accumulation of lymphoid tissue in the body; about 25% of the T cell pool and 15% of the B cell pool are there. They are there to react to all the antigens processed by the macrophages lining the Cords of Bilroth. You can think of the white pulp as a gigantic lymph node attached to the circulation. The spleen is especially important as a defence against bacteria that circulate in the blood.
In some people the spleen atrophies. Adults with sickle cell disease have lost theor spleens because of infarction. Patients with systemic lupus erythematosus (SLE) and celiac disease suffer from shrinking spleen. In other condition the spleen has to be removed. Following trauma to the spleen it often has to be removed to stop bleeding. Some surgical operation - say for stomach cancer - require the spleen to be removed to get access to the cancer. Sometimes it is necessary to remove the spleen to stop the destruction ofred cells or platelets. On other occasions the spleen is large and overactive and the removal of the spleen becomes a matter of judgement.
What are the complications of splenectomy? The most serious is overwhelming pneumococcal septicemia, (although other bacteria - Hemophilus Influenzae and meningococcus - can cause a fatal septicemia). To guard against this I prefer belt and braces. I vaccinate against the three bacteria and prescribe penicillin (or erythromycin in the penicillin allergic). This is especially important in CLL where response to vaccination is at best uncertain.
It is also important to take antimalarial prophylaxis in malarial areas.
Another complication is a marked rise in platelet count sometimes to over a million. Some patients have had thromboses at the level and a watch need to be kept. Aspirin may be necessary to prevent thrombosis. We sometimes see an abcess under the diaphragm where the spleen used to be, but I have to admit that it's been a very long time since I have seen one of those.
Finally, nowadays my surgical colleagues have usually performed laparoscopical splenectomy whenever they could.