The spleen is the organ found in the LUQ and has 2 types of tissue or “pulp”:
- White pulp - responsible for normal immune response to infection. Antigen presenting cells (APCs) enter the white pulp and activate T-lymphocytes that are stored there. These T-lymphocytes then activate B-lymphocytes for antibody production. B-lymphocytes are able to detect foreign pathogens and present them to T-lymphocytes. This is known as co-stimulation.
White pulp is also important for encapsulated bacteria. Encapsulated bacteria (n.meningitidis, h.influenzae, s.pneumoniae) have smooth surfaces with negative charges, reducing the ability of phagocytes to attach and engulf the bacteria. White pulp help opsonise these bacteria.
- Red pulp - this is 80% of the parenchyma of the spleen. It is made up of tissue known as cords that are rich in macrophages. Red pulp helps removal of old RBCs, phagocytosis of opsonise bacteria, sequestration of platelets, storage of RBCs (in hypovolaemia), and it is also haematopoietic prenatally (until 5 months of gestation).
Causes for functional hyposplenism are:
- Coeliac disease - this is due to excessive loss of lymphocytes through the inflamed enteric mucosa which leads to reticuloendothelial atrophy.
- Sickle-cell disease
- Thalassemia major
- IBD
- Graves disease
- SLE
- Amyloidosis
Other causes include: bone marrow transplantation (graft-versus-host disease), splenectomy, congenital asplenia.
😷 Presentation and investigations
- Increased risk of infections - especially encapsulated bacteria. The severity of infections are also a lot worse.
- Howell-Jolly bodies - nuclear remnants that are found in the RBCs.
- Siderocytes
- Pappenheimer bodies
These are the hallmarks of hyposplenism on peripheral blood smear.
🏆 Diagnosis is difficult. The most sensitive test is a radionucleotide labelled RBC scan.
Ultrasound or CT may also be used
Splenectomy may occur due to:
- Elective surgery
- Haemolytic anaemias
- Idiopathic thrombocytopenia purpura
- Lymphoma and leukaemia
- Splenic cysts, hyatid cysts, splenic abscesses
- Hypersplenism (hereditary spherocytosis or elliptocytosis)
- Emergency surgery
- Trauma (25% of trauma cases are iatrogenic, rib fractures may also cause trauma)
- Rupture (with EBV infection).
It is performed laparoscopically most of the time.
Post-splenectomy prophylaxis
Following a splenectomy patients are particularly at risk from encapsulate organisms such as:
- Pneumococcus
- Haemophilus
- Meningococcus
- Neisseria meningitidis
- Capnocytophaga canimorsus - from dog bites.
Vaccination is given as prophylaxis (if it is elective splenectomy, it should be given 2 weeks prior to surgery):
- Annual influenza vaccination
- Pneumococcal vaccine every 5 years
- Hib
- MenB and MenC
Antibiotic prophylaxis
Penicillin V - 500mg Od. Generally accepted that it should be given for at least 2 years, but often continued for life.
Erythromycin - if allergic to penicillin.
🚨 Complications
- Haemorrhage - often from short gastric or splenic vessels.
- Pancreatic fistula
- Thrombocytosis - aspirin may be given to prevent this.
- Post-splenectomy sepsis - this is because there is a lack of detection from the immune system which can allow the bacteria to proliferate and disseminate.