biology

Overwhelming post-splenectomy infection

Overwhelming post-splenectomy infection is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Overwhelming post-splenectomy infection rather than just read about it. In short: An overwhelming post-splenectomy infection (OPSI) is a rare but rapidly fatal infection occurring in individuals following removal (or permanent dysfunction) of the spleen. The infections are typically characterized by either meningitis or sepsis, and are caused by encapsulated organisms including Streptococcus pneumoniae.

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Reference excerpt

An overwhelming post-splenectomy infection (OPSI) is a rare but rapidly fatal infection occurring in individuals following removal (or permanent dysfunction) of the spleen. The infections are typically characterized by either meningitis or sepsis, and are caused by encapsulated organisms including Streptococcus pneumoniae. It is a medical emergency and requires immediate treatment. Death has been reported to occur within 12 hours. The spleen is necessary for protection against encapsulated bacteria and when removed by splenectomy it can lead to rapid infection by encapsulated bacteria. It rapidly progresses from mild viral symptoms to sepsis. Another source of infection are species of Babesia, which are tick-borne parasites that cause babesiosis.

Signs and symptoms OPSI may initially present with mild viral symptoms such as fever or coughing, however later in infection symptoms may include shakes, shivers, chills, diarrhea, vomiting, malaise, myalgia, headache and abdominal pain. The disease progresses rapidly from the above mentioned symptoms to coma to refractory septic shock and finally death in as little as 24 hours.

Mechanism The spleen contains many macrophages (part of the reticuloendothelial system), which are immune cells that phagocytose and destroy bacteria. In particular, these macrophages are activated when bacteria are bound by IgG antibodies (IgG1 or IgG3) or the complement component C3b. These types of antibodies and complement are immune substances called opsonizers, molecules that bind to the surface of bacteria to facilitate phagocytosis. When the spleen is no longer present (asplenia), IgG and C3b are still bound to bacteria, but they cannot be removed from the blood circulation due to the loss of the splenic macrophages. Hence the bacteria are free to cause infection. Patients without a spleen often need immunizations against pathogens that normally require opsonization and phagocytosis by macrophages in the spleen. These include common human pathogens with bacterial capsules (Streptococcus pneumoniae, Salmonella typhi, Neisseria meningitidis, E. coli, Hemophilus influenzae, Streptococcus agalactiae, Klebsiella pneumoniae, Pseudomonas aeruginosa). Capsules made of polysaccharides (sugars) permit bacteria to evade phagocytosis by macrophages alone, since only proteins are directly recognized by macrophages in phagocytosis. So humoral immunity in forms of IgG and complement proteins is the human immune system's response against bacterial capsules.

Prevention Measures to prevent OPSI include vaccination, prophylactic antibiotics and patient education.

Patient education Knowledge of the risks of asplenia correlates with a greatly reduced risk of OPSI, thus patient education is vital to preventing OPSI and may be the most important factor for preventing OPSI. More and more people are increasingly getting their healthcare information from the internet and the lack of reliable, readable and comprehensive information on the risks of asplenia and splenectomy poses a preventable risk factor for asplenic individuals. The majority (as many as 84%) of asplenic individuals are unaware of the risks of asplenia. Encouraging the wearing of bracelets with information about the condition, the carrying of antibiotics, seeking medical advice before travel, especially to places where malaria and babesia is endemic and seeking immediate medical attention following a bite from an animal has been shown to reduce OPSI risk.

Vaccination The Centers for Disease Control and Prevention's annual vaccine recommendations includes specifics for individuals without a functioning spleen. The Green Book (immunisation guidance, UK) in chapter 7 covers immunisation of people with underlying medical conditions that affect immunity which includes asplenic patients. As there are a range of different pneumococcal vaccines, the patient should be offered the most up to date ones (typically 23 valent polysaccharide vaccine and 13 valent conjugate vaccine), if they have not had them already as part of standard schedule. Repeat doses are recommended in patients without a spleen. The CDC recommends against live vaccines and has specific advice for travellers, which includes malaria avoidance for asplenic individuals.

Prognosis OPSI is almost always fatal without treatment, but modern treatment has decreased the mortality to approximately 40–70 percent. Individuals with OPSI are most commonly treated with antibiotics and supportive care.

Epidemiology The risk of OPSI is 0.23–0.42 percent per year, with a lifetime risk of 5 percent. Most infections occur in the first few years following splenectomy, but the risk of OPSI is lifelong. The risk is greatest for children and elderly (70+ years old), but it can happen at any age. Greater risk is associated with splenectomy for hematological conditions such as sickle cell anemia, thalassemia and tumours when compared to splenectomy due to trauma.

References

Worked examples

Example 1 — a first encounter with Overwhelming post-splenectomy infection

Start with the simplest possible case. Write down what Overwhelming post-splenectomy infection claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Overwhelming post-splenectomy infection before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Overwhelming post-splenectomy infection ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Overwhelming post-splenectomy infection

In research: Overwhelming post-splenectomy infection appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Overwhelming post-splenectomy infection in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Overwhelming post-splenectomy infection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacterial diseases, Medical emergencies, Spleen (anatomy), so understanding it makes those chapters shorter.
In everyday life: Look for Overwhelming post-splenectomy infection outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Close the page and write down what Overwhelming post-splenectomy infection means in your own words.
Compare your version with the excerpt and mark what you missed.
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Frequently asked questions

What is Overwhelming post-splenectomy infection in simple terms?

Why does Overwhelming post-splenectomy infection matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Overwhelming post-splenectomy infection?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Overwhelming post-splenectomy infection.