Spleen Flashcards
Which surface does the spleen have impressions on?
Medial surface
What are the impressions on the medial surface of the spleen?
Gastric impression
Renal impression
Colic impression
Where does the spleen lie in relation to the stomach?
Lies behind the stomach
Where does the spleen lie in relation to the kidneys and colon?
Lies above the kidneys and colon
What is the blood supply of the spleen?
Aorta
coeliac trunk branches off aorta
splenic artery branches off coeliac trunk
What is the blood drainage of the spleen?
Splenic vein
exits spleen
feeds into hepatic portal vein
Where do blood vessels enter and leave the spleen?
Hilum located on medial surface
What is the spleen made up of?
Red pulp
White pulp
What is red pulp made up of?
Sinuses - large capillaries, gaps in their endothelium
endothelium is lined by macrophages
and cords of connective tissue
What is white pulp made up of?
Similar structure to lymphoid follicles
so germinal centre, B cells etc.
Which parts of the spleen do the different blood components pass through?
Red cells preferentially pass through red pulp
White cells and plasma preferentially pass through white pulp
What are the four main functions of the spleen?
Macrophages remove old, damaged, abnormal red blood cells from blood
destroy them by phagocytosis
Pooling of blood
Extramedullary haemopoiesis
Immunological function
What is the use of pooling of blood in the spleen?
Platelets and red cells can be rapidly mobilised during bleeding
When does extramedullary haemopoiesis occur?
Bone marrow fails
Cells are dying quickly
How does the spleen have an immunological function?
Contains significant amount of body’s T cells and B cells
What is splenomegaly?
Enlarged spleen
How do you examine for splenomegaly?
Palpate at right iliac fossa
move hand diagonally upwards, palpate at regular intervals
What are the results of an examination if there actually is splenomegaly?
Can palpate spleen below the costal margin
which is always abnormal
How does the spleen move during inspiration? Why?
Moves downwards as lungs expand and diaphraghm moves downwards
What can cause splenomegaly?
Over working red pulp
Over working white pulp
Extramedullary haemopoiesis
Infiltration
What might cause an over-working red pulp?
Haemolytic anaemia
defective red blood cells being removed from blood
What might cause an over-working white pulp?
Infection
What can infiltrate the spleen?
Cancer cells of blood origin e.g. leukaemia, lymphoma
Cancer metastases
Sarcoidosis - granulomas
Splenomegaly due to infiltration by leukaemia, lymphoma cells involves expansion of which part of the spleen specfically?
White pulp
How is splenomegaly classified?
Massive
Moderate
Mild
What are the causes of massive splenomegaly?
Myelofibrosis
Chronic malaria
What are the causes of moderate splenomegaly?
Lymphoproliferative disorders
myeloproliferative disorders
Portal hypertension
Infections e.g. EBV
How does portal hypertension lead to splenomegaly?
Increased blood pressure in portal vein
blood backs up in splenic vein
raised hydrostatic pressure, less reabsorption of fluid
oedema in spleen
What are the causes of mild splenomegaly?
Infections e.g. hepatitis
Infiltration e.g. sarcoidosos
Autoimmune diseases
What are the complications of splenomegaly?
Hypersplenmism
Rupture
Infarction
What is hypersplenism?
Blood pools in the enlarged spleen more than usual
What can hypersplenism lead to?
Thrombocytopenia
Pancytopenia
Why is the spleen more prone to rupture with splenomegaly?
No longer entirely protected by ribcage
What happens if the spleen ruptures?
Haematoma - large blood clot forms
Anaemia - loss of red cells from blood
Hypotension - reduced blood volume reduces pressure
Why is the spleen more prone to infarction with splenomegaly?
Spleen demands more blood because it’s enlarged
if demand not met, ischaemia and infarction occur
What do splenic infarctions look like?
White
Wedge-shaped
What do multiple splenic infarctions lead to?
Hyposplenism
Spleen shrinks
What is hyposplenism?
Lack of functioning splenic tissue
reduced spleen function overall
What are the causes of hyposplenism?
Splenoctomy - surgical removal of spleen
Sickle cell disease
How can sickle cell disease lead to hyposplenism?
Sickle cells block capillaries in spleen
lead to ischaemia, multiple infarcts, healing by fibrosis
What is seen on a blood film of someone with hyposplenism?
Howell-Jolly bodies
What are Howell-Jolly bodies?
Remnants of DNA in red blood cells
Why do Howell-Jolly bodies show up with hyposplenism?
Spleen would normally remove and destroy red blood cells with DNA remnants
But in hyposplenism, this isn’t happening
such cells remain in the blood
What is the cause of Howell-Jolly bodies?
Errors of erythropoiesis
What are patients with hyposplenism at risk of?
Overwhelming sepsis
particularly by encapulsated bacteria
What are some examples of encapsulated bacteria that people with hyposplenism are at risk of?
Strep. pneumoniae
Neisseria meningitidis
Haemophilus influenzae
