Hyposplenism and Splenectomy

Introduction

The spleen is not a redundant organ. It performs two functions that are difficult to replace: it acts as a mechanical and immunological filter removing encapsulated bacteria and abnormal red cells from the circulation, and it is a major site of antibody production and immune memory. Losing splenic function therefore creates a specific, lifelong vulnerability to a defined set of infections.¹

Crucially, hyposplenism is not confined to patients who have had a splenectomy. A functionally hyposplenic patient with an anatomically present spleen - most importantly in sickle cell disease and coeliac disease - carries the same risks and needs the same prophylaxis, but is far more likely to have it overlooked.

Causes

Surgical (asplenia)

• Trauma - splenic rupture, historically the commonest indication, though conservative management is now preferred where possible
• Haematological disease - hereditary spherocytosis, refractory immune thrombocytopenic purpura, autoimmune haemolytic anaemia, hypersplenism
• Malignancy - lymphoma, or as part of another operation (e.g. distal pancreatectomy, gastrectomy)
• Splenic infarction, abscess or aneurysm

Functional hyposplenism (spleen present but not working)

• Sickle cell disease - repeated splenic infarction causes progressive autosplenectomy, typically complete by early adulthood; these children are at highest risk of pneumococcal sepsis in the first few years of life
• Coeliac disease - a frequently forgotten cause of functional hyposplenism, and a reason to check the blood film and consider vaccination
• Inflammatory bowel disease
• Amyloidosis
• Autoimmune disease - systemic lupus erythematosus, rheumatoid arthritis
• After haematopoietic stem cell transplant, or following splenic irradiation
• Congenital asplenia, including as part of heterotaxy syndromes

Recognising hyposplenism on the blood film

Because functional hyposplenism has no outward signs, the blood film is often what reveals it - and recognising these features can prompt life-saving prophylaxis in a patient nobody realised was at risk.

• Howell-Jolly bodies - the classic finding; small, round, dark-staining nuclear remnants within red cells. A normally functioning spleen 'pits' these out, so their presence signals splenic dysfunction
• Target cells (codocytes)
• Pappenheimer bodies - iron-containing granules
• Acanthocytes - spiculated red cells
• Reactive thrombocytosis - the platelet count often rises substantially after splenectomy, since a third of the platelet mass is normally pooled in the spleen
• Lymphocytosis and monocytosis

Overwhelming post-splenectomy infection

OPSI is the reason all of this matters. It is a fulminant septicaemia that can progress from a mild flu-like prodrome to shock, DIC and death within 24-48 hours, with a mortality of up to 50% even with intensive care.²

Why encapsulated organisms

Encapsulated bacteria resist phagocytosis unless they are first opsonised by antibody and complement, and cleared by splenic macrophages. Without a spleen, this clearance mechanism is lost, and the organisms can multiply unchecked in the bloodstream.

Risk is highest in the first 2 years after splenectomy and in children, but it is lifelong - cases occur decades later, which is why prophylaxis and education must not lapse.

Prevention

Vaccination

• Pneumococcal vaccination - the single most important; given according to current UK schedule, with revaccination as recommended
• Haemophilus influenzae type b (Hib)
• Meningococcal ACWY and MenB
• Annual influenza vaccination - important both directly and because influenza predisposes to secondary bacterial pneumonia
• Timing: ideally at least 2 weeks before elective splenectomy, to allow an adequate antibody response while the spleen is still functioning. After an emergency splenectomy, vaccinate from 2 weeks post-operatively
• Ensure the routine immunisation schedule is otherwise complete, and keep vaccinations up to date lifelong

Antibiotic prophylaxis

• Phenoxymethylpenicillin (penicillin V) is first line; a macrolide (e.g. erythromycin or clarithromycin) if penicillin-allergic
• Duration: recommended lifelong for high-risk patients (children, the first 2 years after splenectomy, immunosuppressed patients, and those with a previous episode of invasive pneumococcal disease). Practice varies for lower-risk adults after 2 years, and the decision should be individualised and clearly documented
• A rescue ("just in case") supply of a broad-spectrum antibiotic - typically co-amoxiclav - for the patient to keep at home and start immediately if they develop a fever and cannot access medical care quickly, particularly when travelling

Education and documentation

• Splenectomy/asplenia card and a medical alert bracelet, so that any clinician encountering them recognises the risk
• Clear advice that any fever is a medical emergency requiring same-day assessment - patients must understand that they can deteriorate over hours rather than days
• Travel and malaria advice - rigorous chemoprophylaxis and bite avoidance, since malaria is far more severe without a spleen
• Animal bite advice - seek prompt medical attention and antibiotic cover for any bite, given Capnocytophaga risk
• Inform the GP and ensure it is coded in the primary care record, so prophylaxis and vaccination are maintained lifelong
• Dental and surgical procedures - discuss whether additional antibiotic cover is needed

Management of the febrile hyposplenic patient

• Immediate empirical IV antibiotics covering encapsulated organisms, following the local sepsis and asplenia protocols
• Blood cultures, FBC, U&Es, LFTs, CRP, lactate and clotting - and a blood film, which may show organisms within red cells in severe pneumococcal sepsis or malaria
• Malaria films if there is any travel history
• Fluid resuscitation and early critical care involvement if there is any evidence of shock
• A low threshold for admission - do not discharge a febrile hyposplenic patient on oral antibiotics without senior review

Other consequences of splenectomy

• Thrombocytosis - the platelet count commonly rises markedly after splenectomy; thromboprophylaxis is important perioperatively, and some patients need antiplatelet therapy if counts are extremely high
• Increased venous thromboembolism risk, including portal vein thrombosis in the early post-operative period - consider it in any post-splenectomy patient with abdominal pain
• Surgical complications - bleeding, pancreatic tail injury, subphrenic abscess, and (with open surgery) the usual wound complications
• Persistent haematological disease if an accessory spleen is present - a residual accessory spleen can cause treatment failure after splenectomy for ITP or spherocytosis, and is suggested by the absence of Howell-Jolly bodies in a patient who has had a splenectomy
• Pulmonary hypertension - a recognised long-term association in some patient groups

Red flags

Prognosis

With complete vaccination, adherent antibiotic prophylaxis and good patient education, most people without a functioning spleen live entirely normal lives with normal life expectancy. The absolute annual risk of overwhelming infection is low - but the case fatality when it occurs is very high, which is what justifies the intensity of preventive measures.²

Risk is greatest in children, in the first two years after splenectomy, and in the immunosuppressed, but never returns to that of the general population. Because the risk persists for life while awareness tends to fade with time, the most valuable long-term interventions are the least technological: an accurate primary care record, a splenectomy card the patient actually carries, up-to-date vaccinations, and a patient who genuinely understands that a fever means seeking help the same day.