Asplenia

Snapshot | Asplenia

• A 13-year-old girl presents to her primary care physician for follow-up care of her recently diagnosed hereditary spherocytosis. She reports increasing fatigue and shortness of breath. She required a blood transfusion approximately 4 months prior to presentation. She has not received the PCV13 vaccine but has received the PPSV23 vaccine on year ago. Physical examination shows pallid conjunctiva and organomegaly in the left upper quadrant. Laboratory testing is significant for an elevated reticulocyte count and serum bilirubin. A decision has been made among the patient, her family, and physician to undergo an elective splenectomy. She is administred the PCV13 vaccine 14-days before her operation.

Introduction

Asplenia, also known as hyposplenism or absence of the spleen, is a medical condition characterized by the partial or complete absence of the spleen. This condition can have significant implications for the immune system, blood clotting, and overall health. Understanding asplenia is crucial for medical professionals, especially those in hematology, immunology, and internal medicine. This article provides a comprehensive overview of asplenia, including its types, function, related studies, treatment considerations, and clinical significance.

• Clinical definition
  • absence of normal spleen function that can be secondary to
    • surgical splenic removal
    • congenital absence or abnormally reduced spleen
    • splenic infarction such as in
      • sickle cell disease and thrombosis of the splenic artery
    • splenic infiltration such as in
      • sarcoidosis, malignancy, and amyloidosis
• Under normal conditions
  • the spleen is involved in
    • filtering the blood through a series of capillaries, which results in
      • the removal of rigid erythrocytes
      • ingestion of circulating bacteria
  • the spleen is a lymphoid organ that contains
    • B-lymphocytes which is involved in
      • producing opsonizing antibodies against foreign materials which is vital for
        • eliminated encapsulated organisms
• Patients with absent splenic function are therefore
  • at risk of infection by encapsulated organisms such as
    • Streptococcus pneumoniae (most important) 
    • Haemophilus influenzae
    • Neisseria meningitidis
  • other infectious agents include
    • Capnocytophaga canimorsus
      • patients are at risk when exposed to dogs
• Babesia

Presentation

• Physical exam
  • in cases of sepsis
    • toxic appearing
    • tachycardia
    • evolving hypotension
• altered sensorium

Studies

• Labs
  • blood smear will show
    • Howell-Jolley bodies 
    • target cells 
  • complete blood cell count (CBC) can show
    • leukocytosis
• thrombocytosis

Treatment

• Conservative
  • immunization
    • indication
      • should be administered at least two weeks before a scheduled splenectomy
      • should be administered two weeks after splenectomy in patients who
        • were not able to receive pre-operative immunization
    • modality
      • PCV13 and PPSV23 is recommended for both adults and children
• Medical
  • antibiotic prophylaxis 
    • indication
      • this is the mainstay and initial treatment for infection prophylaxis in asplenic patients
      • children should receive daily antibiotic prophylaxis (amoxicillin or penicillin VK) until
        • the age of five and
          • at least one year post-splenectomy
      • must be taken when fever or rigors is present in asplenic patients since this is
        • can be a warning sign for fulminant bacteremia
        • antibiotics include
          • amoxicillin-clavulanate or cefuroxime in children
• fluoroquinolone (e.g., levofloxacin) in adults

Complications

• Sepsis due to
• infection by encapsulated organisms

Types of Asplenia:

1. Congenital Asplenia: Some individuals are born without a spleen due to developmental anomalies. This condition can be associated with other congenital abnormalities.
2. Acquired Asplenia: Acquired asplenia can result from surgical removal of the spleen (splenectomy) due to conditions like trauma, splenic tumors, or certain blood disorders.

Function of the Spleen:

The spleen plays several crucial roles in the body:

1. Immune Function: The spleen filters blood and helps remove damaged or old blood cells and pathogens. It also plays a role in immune responses against infections.
2. Blood Storage: The spleen stores platelets and red blood cells, releasing them into circulation when needed.
3. Blood Filtration: The spleen helps filter blood by removing debris and foreign particles.

Clinical Significance:

1. Increased Infection Risk: Asplenia can lead to an increased risk of severe bacterial infections, particularly caused by encapsulated bacteria like Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis.
2. Thromboembolic Events: Without the spleen’s blood-filtering function, there is a potential risk of clot formation and thromboembolic events.

Asplenia Studies:

1. Infection Risk Studies: Research investigates the susceptibility of individuals with asplenia to bacterial infections and explores preventive measures.
2. Vaccine Efficacy Studies: Studies assess the effectiveness of vaccines, such as pneumococcal and meningococcal vaccines, in individuals with asplenia.

Treatment Considerations:

1. Vaccination: Individuals with asplenia are often recommended to receive vaccines to protect against infections caused by encapsulated bacteria.
2. Prophylactic Antibiotics: In some cases, prophylactic antibiotics may be prescribed to reduce the risk of bacterial infections.
3. Education and Awareness: Patients with asplenia should be educated about the risks of infections and instructed on seeking prompt medical attention for fever or signs of infection.

Future Directions:

1. Immunization Strategies: Research explores optimized vaccination strategies to provide effective protection for individuals with asplenia.
2. Novel Therapies: Investigative therapies may target the immune system to enhance protection against infections.

Conclusion:

Asplenia, characterized by the partial or complete absence of the spleen, can result from congenital anomalies or acquired conditions like splenectomy. The spleen plays critical roles in immune function, blood filtration, and storage. Individuals with asplenia face increased susceptibility to severe bacterial infections, particularly those caused by encapsulated bacteria. Research focuses on understanding infection risks, vaccine effectiveness, and preventive measures. Vaccination, prophylactic antibiotics, and patient education are essential aspects of managing asplenia.

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