In most cases, when the spleen is removed for blood disorders (spherocytosis, elliptocytosis, idiopathic thrombocytopenic purpura (ITP), sickle cell anemia), the spleen is functioning perfectly normally and the abnormalities of the blood are producing the problem.
Anemia
The normal red cell is disk shaped and as it ages, the internal membranes break down and the cell assumes a spherical shape and is removed by the spleen about 100 days after it is created.
In conditions called spherocytosis and elliptocytosis, this change in the cell shape occurs at a much younger age of the cell leading to its premature destruction. This premature destruction results in anemia (low red cell count) and an increased risk of developing gallstones.
Gallstones
The hemoglobin in the broken-down red blood cells is then excreted as bilirubin in the bile from the liver. If the level of bilirubin in the bile is too high, it will result in gallstone production.
ITP
In idiopathic thrombocytopenic purpura (ITP), the platelets are often coated with antibody, which has been mistakenly produced by the body's immune system.
This coating of the platelets with antibody leads the spleen to see them as foreign and filter them from the blood, leading to excessive destruction.
Sickle cell anemia
Some children can develop a life-threatening crisis where blood pools in the spleen, which becomes enlarged.