What is the role of the spleen and what are some related emergencies?

Role of the Spleen and Related Emergencies

The spleen is a vital organ that performs critical immunological and hematological functions, and splenic emergencies require prompt recognition and management to prevent potentially fatal outcomes such as overwhelming post-splenectomy infection (OPSI) and hemorrhagic shock from splenic rupture. 1, 2

Functions of the Spleen

The spleen serves two major functions:

Immunological Functions

• Acts as a secondary lymphoid organ responsible for regulation of immune responses 3
• Combines innate and adaptive immunity in a unique way 4
• Produces antibodies, particularly opsonizing antibodies critical for bacterial clearance 5
• Maintains populations of IgM memory B cells essential for immune response 3
• Protects against encapsulated bacteria (Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b) 3

Hematological Functions

• Functions as the body's largest blood filter 4
• Removes senescent, damaged, and aberrant cells from circulation 4
• Sequesters bacteria that are poorly opsonized, critical for protection in non-immune hosts 5
• Filters blood to remove pathogens and maintain blood quality 3

Splenic Emergencies

1. Splenic Trauma and Rupture

Presentation

• Hemodynamic instability
• Left upper quadrant pain
• Left shoulder pain (Kehr's sign)
• Signs of peritonitis
• Decreasing hematocrit levels

Management Algorithm

1. Initial Assessment: Evaluate hemodynamic status immediately 1

   • Stable: Consider non-operative management (NOM)
   • Unstable: Proceed to operative management (OM)

2. Imaging for Stable Patients:

   • CT scan with intravenous contrast is the preferred imaging modality 6
   • Classify injury grade and identify active bleeding

3. Treatment Options:

   • Non-operative Management (NOM): Gold standard for hemodynamically stable patients 1

     • Success rate of 80-95% for all grades of blunt injury 6
     • Contraindicated in unresponsive hemodynamic instability or other indications for laparotomy 1

   • Angiography/Angioembolization (AG/AE):

     • First-line intervention for stable patients with arterial blush on CT scan 1
     • Both proximal and distal embolizations are effective 6

   • Operative Management (OM):

     • Indicated for hemodynamically unstable patients 1
     • Required when NOM fails with significant drop in hematocrit or continuous transfusion needs 1
     • Splenectomy is preferred when NOM with AG/AE fails 1

Risk Factors for NOM Failure

• Age >55 years
• High Injury Severity Score (ISS)
• Moderate to severe splenic injuries
• Large hemoperitoneum
• Hypotension before resuscitation
• GCS <12
• Low hematocrit at admission
• Associated abdominal injuries
• Contrast blush on CT scan 1

2. Overwhelming Post-Splenectomy Infection (OPSI)

Presentation

• Rapid onset of fever, chills
• Headache, altered mental status
• Hypotension, shock
• Disseminated intravascular coagulation (DIC)
• Mortality rate up to 50-70% 2

Causative Organisms

• Primarily encapsulated bacteria:
  • Streptococcus pneumoniae (most common)
  • Neisseria meningitidis
  • Haemophilus influenzae type b 2, 3

Management

1. Immediate Intervention:

   • Fluid resuscitation
   • Empiric broad-spectrum antibiotics
   • Blood cultures and sensitivity testing
   • Blood glucose, renal function, and electrolyte monitoring 2

2. Prevention Strategies:

   • Vaccination against encapsulated bacteria
   • Antibiotic prophylaxis
   • Patient education about infection risks 2, 3

3. Splenic Infarction

Presentation

• Left flank pain
• Left upper quadrant pain
• Back pain
• Fever in some cases 7

Diagnosis

• CT or MRI with 90-95% sensitivity and specificity
• Appears as peripheral low-density, wedge-shaped areas on CT 7

Management

• Limited activity for 3 weeks to 3 months depending on severity
• Monitor for complications
• Differentiate from splenic abscess (persistent fever, positive blood cultures, enlarging splenic defects) 7

4. Other Splenic Emergencies

• Splenic Sequestration Crisis: Life-threatening complication in sickle cell disease 7
• Splenic Abscess: Requires antibiotics and possible drainage or splenectomy
• Spontaneous Splenic Rupture: Can occur in infectious mononucleosis, malaria, and hematologic malignancies
• Portal Hypertension with Splenic Vein Thrombosis: Can lead to gastric varices and bleeding

Special Considerations

Post-Splenectomy Care

• Vaccination: Required against encapsulated bacteria
• Antibiotic Prophylaxis: Especially important in the first 2 years post-splenectomy
• Patient Education: Recognition of early signs of infection
• Activity Restrictions: Avoid contact sports to decrease risk of trauma to accessory spleens 7

Monitoring

• Regular blood count monitoring every 6-12 months
• Abdominal ultrasound every 6 months for patients with underlying conditions 7

Pitfalls to Avoid

• Failing to recognize malignant infiltration in massive hepatosplenomegaly
• Overlooking splenic sequestration as a life-threatening complication
• Underestimating risks of splenectomy in patients with portal hypertension
• Performing splenectomy in patients with severe thrombocytopenia that may indicate impending leukemic transformation 7