Spleen Flashcards
What is the Fx of the spleen
Red pulp:
- MOs capture and break down defective RBCs/platelets via phagocytosis
- Fetalerythropoiesis
- Sequestration ofplatelets: up to⅓ of body’splateletsare stored in spleen
While Pulp
Lymphatic tissue of spleen → mounts immune response toblood-borneantigensand infections
- After maturation in primary lymphatic organs, LOsmigrate into spleen and lie dormant until activation → after differentiation to effector cells, activated B and T LOs reenter bloodstream via red pulp to mount immune responsein inflamed tissue
- MOs and otherAPCsin PALS and marginal zone trapAgfrom circulation and present it to LOs of spleen
- SplenicMOs capture opsonised encapsulated bacteria→ opsonisation body’s primary defence againstencapsulated bacteria
- B LOs in follicles differentiate into plasma cells which produce antibodies (e.g., IgM) and for memory cells
- Spleen = major site ofIgM productionin body
How does splenectomy increase pt susceptibility to certain organisms and which ones
Encapsulated organisms e.g., haemophilus influenza, neisseria meningiditis, streptococcal pneumonia
Reduced IgM production –> reduced complement activation and C3b opsonisation of encapsulated organisms
What are some common causes of splenomegaly
Infection
1. Acute e.g., septic shock, infectious endocarditis, EBV, typhoid, CMV
2. Chronic e.g., TB, brucellosis, HIV
3. Parasitic e.g., malaria, schistosomiasis
Inflammation
1. Rheumatoid arthritis (Felty syndrome)
2. SLE
3. Sarcoidosis
4. Serum sickness
Haematological
1. Haemolytic anaemia
2. Haemoglobinopathies
3. Myeloproliferative disorders
4. Leukaemia
5. Lymphomas
Congestion
1. Splenic vein thrombosis/obstruction
2. Portal vein obstruction e.g., hepatic cirrhosis
3. Constrictive pericarditis
4. Congestive heart failure
5. Hepatic vein obstruction
Infiltrative
1. Amyloidosis
2. Sarcoidosis
3. Gaucher’s disease
Neoplasia
1. Primary and secondary neoplasia
NB. Massive splenomegaly chronic myeloid leukaemia, myelofibrosis, chronic malaria and rarely Gaucher’s disease
What are the results of hypersplenism
Overactive spleen → cells removed from blood faster thannormal →↓ ofa single or combination of cell lines, including possiblecytopenia (pancytopenia, leukopenia, anaemia, thrombocytopaenia) → reactive bone marrow hyperpalsia (unless defective BM is cause of splenomegaly)
→ increased risk of bleeding, infection, pallor, fatigue, signs of haemolysis
→ splenomegaly
What is a splenectomy
A surgical procedure (laparoscopic or open) consisting of partial or total removal of spleen.
What are the indications for splenectomy
Indications include spleen rupture, significant splenomegaly or hypersplenism, and certain hematologic disorders and malignancies.
- Trauma resulting from an accident or during a surgical procedure e.g., during mobilisation of oesophagus, stomach, distal pancreas or splenic flexure of colon
- Removal en bloc with stomach as part of a radical gastrectomy or with pancreas as part of a distal or total pancreatectomy
- To reduce anaemia or thrombocytopenia in spherocytosis, ITP, or hypersplenism
- In association with shunt or variceal surgery for portal HTN
What are the complications of splenectomy
Immediate
- Haemorrhage from slipped ligature
- Haematemesis from gastric mucosal damage and gastric dilatation (uncommon)
- Left basal atelectasis (common) and possible pleural effusion
- Adjacent stomach and pancreas at risk during procedure
- Damage to greater curvature during ligation of short gastric vessels → fistula formation
- Damage to tail of pancreas → pancreatitis, localised abscess or pancreatic fistula
- Postoperative thrombocytosis may arise → if platelet count exceeds 1 x 10^6/mL, prophylactic aspirin recommended to prevent axillary or other venous thrombosis
- Post-splenectomy septicaemia may result from streptococcus pneumoniae, neisseria meningitides, haemophilus influenzae and escherichia coli
- Higher risk: young pts, pts Tx with chemoradiotherapy, pts who have undergone splenectomy for thalassaemia, sickle cell disease and autoimmune anaemia or thrombocytopenia
Opportunistic Post-Splenectomy Infection (OPSI)
Subphrenic abscess
What is post-splenectomy OPSI and what is the risk
Opportunistic Post-Splenectomy Infection (OPSI) = a bacterial infection that rapidly progresses to fulminant, overwhelmingsepsisin the setting of anatomic orfunctional asplenia
- Risk of overwhelming asplenic sepsis greatest within first 2-3yrs post-splenectomy but increased risk of fulminant andlife-threateninginfections and sepsis for up to30 yearsor longer aftersplenectomy
Prognosis → mortality 70% w/out Tx but reduced to ~10-40% with early Tx
Most infections could be avoided through appropriate and timely immunisation, antibiotic prophylaxis, education and prompt treatment of infection
How does OPSI present
Clinical:initially flu-like Sx → rapid deterioration within hourswithfever, severemalaise, signs of sepsis, and meningitis
What is the cause and pathophysiology of OPSI
Aetiology: Encapsulated bacteria e.g., strep pneumoniae, neisseria meningiditis, haemophilus influenzae
- Also increased risk of severe malaria if travelling to countries where malaria is present, and overwhelming post-splenectomy sepsis due to capnocytophaga canimorsus from dog, cat or other animal bites.
Pathophysiology: Splenectomy→↓IgM production →↓ complementactivation →↓ C3bopsonisation→↓ clearanceofopsonised bacteria →↑ susceptibilityto infection by encapsulated bacteria
- Normally,encapsulated pathogensareopsonisedwithantibodiesand thenphagocytosed by specialised MOs in spleen
- Individuals with asplenia lack these specialisedMOs so pathogens are able to spread → sepsis
What is a subphrenic abscess
Subphrenic abscess: accumulation of pus located directly under diaphragm (~2% pts post-abdominal surgery) due to polymicrobial infection (e.g., due to enterococcus spp.,e/ coli and clostridiumspp.) followingintraperitonealperforation
- Develops ~3-6wks post-surgery
How does a subphrenic abscess present and what are potential complications
Clinical: fever, pain over ribs 8-11 on affected side, cough, increased RR, pleural effusion
Complications: empyema, sepsis, high mortality
How is a subphrenic abscess Dx and Tx
Diagnostics: leukocytosis, abscess visualised on USS, air below diaphragm on CXR
Tx: drainage and antibiotics
What are the haematological changes that occur in an asplenic patient
Peripheral blood smear: Howell-Jolly bodies (basophilicspots within RBCs; if not → accessory spleen), target cells
Labs: lymphocytosis due to loss of sequestration of LOs in spleen, neutrophilia, decreased production of Ig (IgG, IgM) → decreased complement activation and C3b opsonisation, reactive thrombocytosis usually for the first weeks to months aftersplenectomy (spleenstores~ ⅓of circulatingplatelets filters oldplatelets from bloodstream)
- Transient elevation of platelet and white cell count after splenectomy may mimic sepsis
Describe the aetiology of a traumatically ruptured spleen
MC = Direct blunt abdominal trauma (MC MVA; also contact sports, physical altercations, falls from great heights)
- Consider splenic rupture in any case of blunt abdominal trauma, esp. when LUQ injury
Iatrogenic injury to the spleen remains a frequent complication of any surgical procedure, esp. those in LUQ when adhesions are present
NB. Splenic rupture can also be atraumatic
