Removed spleen. Surgeon holding a greatly enlarged spleen just after its removal from a patient. Enlargement of the spleen (splenomegaly) can be caused by many conditions, including infections such as malaria or typhoid, anaemia, leukaemia and spleen tumours. Enlarged spleens are often over-active (hypersplenism), and start to break down blood cells at a higher rate than usual. This can lead to anaemia, a weakened immune system and clotting disorders. Removal of the spleen has little effect on adults, as its function, the removal of old blood cells, is largely taken over by the liver.