6. The spleen Flashcards
Where is the spleen located?
left upper quadrant of abdomen
What does the spleen consist of?
- Red pulp: sinuses lined by endothelial macrophages and cords
- White pulp: similar structure to lymphoid follicles
How does blood enter and travel through the spleen?
- Enters via splenic artery.
- White cells and plasma preferentially pass through white pulp
- Red cells preferentially pass through red pulp
What is the function of the spleen?
- blood filter: old/abnormal RBCs sequestered and phagocytosed by macrophages in red pulp (also metabolises the Hb)
- immunological function: 25% of T cells and 15% of B cells present in white pulp - synthesises antibodies, removes antibody-coated bacteria and blood cells
- blood pooling: platelets and RBCs can be rapidly mobilised during bleeding
- extramedullary haemopoiesis: pluripotent stem cells proliferate during haematological stress or if marrow fails (e.g. myelofibrosis)
How does one measure and assess splenomegaly?
‘Never’ normal to palpate spleen below the costal margin.
- start to palpate at right iliac fossa (or will miss massive splenomegaly)
- feel the spleen edge move towards your hand on inspiration, feel for splenic notch
- measure spleen in cm from costal margin in mid-clavicular line
Give reasons for splenomegaly.
- over-working red pulp, e.g. in haemolytic anaemia where an increased number of defective RBCs are removed from circulation
- over-working white pulp, e.g. in infection
- congestion due to portal hypertension in liver disease causing back pressure
- extramedullary haemopoiesis (reverts to previous function)
- infiltration of abnormal cells
- cancer cells of blood origin (e.g. chronic lymphocytic leukaemia expands white pulp nodules)
- other cancer metastases - infiltration of other material, e.g. sarcoidosis (granuloma formation) or Gaucher’s disease (defect in beta-glucosidase enzyme which catalyses breakdown of glucocerebroside causing its accumulation in fibrils)
Name 3 possible complications of splenomegaly.
- hypersplenism - pooling of blood in enlarged spleen and increased activity can cause pancytopenia or thrombocytopenia
- risk of rupture if enlarged and no longer protected by rib cage… haematoma
- infarction - problems with delivery of blood in small capillaries
What is hyposplenism?
lack of functioning splenic tissue
Name 3 causes for hyposplenism.
- splenectomy
- sickle cell disease in older children and adults (due to multiple infarcts then fibrosis)
- coeliac disease (underactive spleen)
What finding is characteristic of hyposplenism in blood films?
Howell Jolly bodies (DNA remnants in circulating RBCs) - as abnormal cells not being filtered and destroyed
What is the major risk for hyposplenic/asplenic patients?
overwhelming sepsis, esp. from encapsulated organisms such as Meningococcus, Pneumococcus and Haemophilus influenzae
