Asplenia

The spleen plays a crucial role in immune function, blood filtration, and platelet storage. Asplenia is the absence of splenic tissue or function and can stem from several factors ranging from congenital to iatrogenic. There is a distinction between anatomic asplenia, which is due to the surgical removal of the spleen, and functional asplenia, which is due to a condition that leads to splenic atrophy, infarct, congestion, or infiltrative disease. Howell-Jolly bodies are commonly seen on peripheral blood smear. Abdominal imaging and scintigraphy are used for diagnosis. High risk of sepsis caused by encapsulated bacteria requires adherence to a strict vaccination schedule and early antibiotic treatment when an infection is suspected. Thromboembolic events are common.

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Overview

Definition

The spleen is one of the secondary lymphatic organs central to immune function that plays a role in filtering the blood and removing old or damaged erythrocytes. Asplenia is defined as the lack of a spleen or splenic function.

Etiology

  • Congenital:
    • Component of heterotaxy syndrome involving organs of the chest and abdomen
    • Autosomal dominant inheritance
  • Functional:
    • Atrophy
    • Infarction
    • Engorgement
    • Infiltration
  • Acquired: 
    • Surgical removal: most common cause 
    • Splenic rupture

Epidemiology

Epidemiology differs based on etiology.

  • Congenital:
    • Rare
    • Syndromic asplenia is predominant in men.
    • Celiac disease, Whipple procedure, and alcoholic liver disease are strongly associated with partial splenic disfunction.
  • Functional asplenia: Nearly all patients with sickle cell disease (and other hemoglobinopathies) will suffer from functional asplenia.
  • Acquired: The incidence of surgical splenectomy is decreasing because of new surgical techniques.

Pathophysiology

  • Functional asplenia typically begins with hyposplenism:
    • Entrapment of RBCs 
    • Infarction
    • Hyposplenism
    • Autosplenectomy
  • Lack of a filtration function for bacteria: increased risk of sepsis due to encapsulated bacteria
    • Haemophilus influenzae
    • Streptococcus pneumoniae
    • Neisseria meningitidis
    • Escherichia coli
    • Klebsiella
  • Increased risk of vascular events:
    • Secondary to thrombocytosis
    • Increased circulation of damaged erythrocytes
Table: Causes of asplenia by category
CategoryDisease/condition
Congenital
  • Heterotaxy syndrome
  • Ivemark syndrome
Iatrogenic
  • Splenectomy (post trauma)
  • Irradiation
Circulatory
  • Splenic artery/vein thrombosis
  • Celiac artery thrombosis
Hematologic/oncologic
  • Sickle cell disease
  • Hereditary spherocytosis
  • Myeloproliferative disorders
  • Graft vs. host disease
  • Malignancy (leukemia, lymphoma, metastases)
Hepatic
  • Alcoholic liver disease/cirrhosis
  • Chronic hepatitis
  • Portal hypertension
Autoimmune
  • Systemic lupus erythematosus
  • Thyroiditis
  • Sarcoidosis
  • Rheumatoid arthritis
GI
  • Celiac disease
  • Inflammatory bowel disease
  • Whipple’s disease
Infectious
  • AIDS
  • Malaria
  • Bacterial infections by Pneumococcus, Haemophilus influenzae, Neisseria
Stage IV splenic injury

Stage IV splenic injury in a 34-year-old patient

Image: “Stage IV Splenic injury in a 34 Year Old Patient” by Eskandarlou, M., Derakhshanfar, A. License: CC BY 3.0

Diagnosis

  • History and physical:
    • History of a predisposing syndrome, condition, or trauma
    • Surgical history
  • Laboratory testing:
    • Peripheral blood smear:
      • Howell-Jolly bodies pathognomonic
      • Heinz bodies, target cells, pitted erythrocytes common
    • CBC:
      • Neutrophilia
      • Thrombocytosis
  • Diagnostic imaging:
    • Plain radiography:
      • Reveals abnormal orientation of organs in heterotaxy syndromes
      • May be helpful in trauma
    • MRI
    • Ultrasound
    • Scintigraphy

Management

Management depends on the underlying cause, degree of asplenia, and age. Patients > 5 years of age have a better prognosis. Prevention of infection is the cornerstone of long-term care because of the increased risk of rapidly progressing septicemia that is fatal in 50% of patients.

Infection control

  • Routine vaccination:
    • Pneumococcal 
    • Meningococcal
    • H. influenzae (type B)
    • Influenza
  • Antibiotic prophylaxis:
    • For 1–2 years after splenectomy
    • Up to 5 years of age
    • Surgical procedures that may predispose to infection by encapsulated bacteria
    • Lifetime, if history of post-splenectomy sepsis
  • Empiric antibiotic treatment: indicated early when a patient presents with fever or other signs of infection

Overwhelming post-splenectomy infection (OPSI)

Rapid-onset septicemia:

  • Infection without definitive source accompanied by DIC
  • Mortality rate: 50%–70%
Management of Fever in an Asplenic Patient

Management of an episode of fever in an asplenic patient

Image by Lecturio. License: CC BY-NC-SA 4.0

Clinical Relevance

  • Blunt abdominal trauma and penetrating abdominal injury: Abdominal injuries are classified as blunt or penetrating, according to the mechanism of injury. Different structures including the duodenum, spleen, liver, kidneys, and pelvic organs can be injured. In severe splenic injury, a splenectomy may have to be performed to remove the spleen.
  • Mononucleosis: also known as “kissing disease,” or infectious mononucleosis. Mononucleosis is a highly contagious viral infection caused by the EBV. The common name for mononucleosis stems from its main method of transmission: the spread of infected saliva via kissing. During acute EBV infections, the spleen can become enlarged and rupture either spontaneously (rare) or owing to its increased vulnerability to trauma.
  • Spleen: a coffee-bean-shaped organ located in the left posterior upper abdomen (epigastric region) and weighing about 150 grams. The spleen is composed of very soft tissue that is filled with blood, which trickles through the parenchyma and filters out any old or abnormal RBCs and WBCs. The spleen also plays a role in immune function by removing pathogens and producing antibodies. Owing to its fragile nature and high vascularization, the spleen can rupture easily during abdominal trauma, particularly when it is enlarged.
  • Splenomegaly: massive enlargement of the spleen, rendering it palpable under the left costal arch. Ultrasounds show a bulging shape and rounding of the normally pointed ends. Any ectopic tissue, such as accessory spleens, will also be hypertrophied. Enlargement of the spleen may occur for different reasons, including infection, internal hemorrhage, or sequestration of abnormal blood cells. Enlargement of the spleen puts it at risk for rupture during trauma.

References

  1. Pulvirenti, F., et al. (2020). Chapter 48. In Sullivan, K., and Stiehm, R. (Ed.), Stiehm’s Immune Deficiencies Inborn Errors of Metabolism. 2nd ed. pp. 1012–1033. Retrieved April 12, 2021, from https://www.sciencedirect.com/topics/immunology-and-microbiology/asplenia
  2. Quinti, I., Paganelli, R. (2014). Chapter 45. In Sullivan, K., and Stiehm, R. (Ed.), Stiehm’s Immune Deficiencies Inborn Errors of Metabolism. 1st ed. pp. 835–844. Retrieved April 12, 2021, from https://doi.org/10.1016/B978-0-12-405546-9.00045-5
  3. Litz, C.E. The post splenectomy blood picture. Retrieved April 16, 2021, from https://propath.com/the-post-splenectomy-blood-picture/
  4. Chen, M.J., Huang, M.J., et al. (2005). Ultrasonography of splenic abnormalities. World Journal of Gastroenterology. 11(26), 4061–4066. Retrieved April 16, 2021, from http://dx.doi.org/10.3748/wjg.v11.i26.4061
  5. Rubin, L., Schaffner, W. (2014). Care of the asplenic patient. New England Journal of Medicine. 371, 349–356. Retrieved April 16, 2021, from https://doi.org/10.1056/NEJMcp1314291

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