50 SPLEEN
# Spleen
👩⚕️ The spleen is a frequent MRCS Part A topic because almost every fact about it doubles as a clinical scenario. Know the two ligaments and their contents, the danger zones during splenectomy, the post-splenectomy blood film, and OPSI prophylaxis. Almost every spleen SBA tests one of these four areas.
Detailed notes
Overview and surface anatomy
The spleen is the largest lymphoid organ and the principal filter of the blood. It is an intraperitoneal organ in the left upper quadrant, tucked behind ribs 9–11 on the left, with its long axis running along the tenth rib. It does not normally extend below the costal margin — a palpable spleen is enlarged at least two- to threefold.
➡ 1, 3, 5, 7, 9, 11 rule ➡ 1 inch thick, 3 inches wide, 5 inches long, weighs 7 oz, lies behind ribs 9 to 11. A simple mnemonic that examiners love.
➡ Embryologically derived from mesoderm of the dorsal mesogastrium, which is why it is intraperitoneal despite developing close to retroperitoneal structures.
Relations
The convex diaphragmatic surface lies against the diaphragm and ribs. The concave visceral surface has impressions for four neighbours:
- Gastric impression — stomach (anteriorly)
- Renal impression — left kidney (posteromedially)
- Colic impression — splenic flexure of colon (inferiorly)
- Pancreatic impression — tail of pancreas, reaching the hilum within the lienorenal ligament
👩⚕️ The tail of pancreas reaches the splenic hilum in roughly 50% of people. It is the structure most at risk during splenectomy and the reason post-splenectomy pancreatic fistula occurs.
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Peritoneal ligaments
Two ligaments anchor the spleen, and both are commonly examined.
| Ligament | Connects | Contents |
|---|---|---|
| Gastrosplenic | Spleen to greater curvature of stomach | Short gastric vessels, left gastroepiploic vessels |
| Lienorenal (splenorenal) | Spleen to posterior abdominal wall over left kidney | Splenic artery, splenic vein, tail of pancreas, lymph nodes |
The phrenicocolic ligament runs from the splenic flexure to the diaphragm and supports the inferior pole of the spleen — it is not a true splenic ligament but is occasionally tested as a distractor.
👩⚕️ Splenectomy danger zones — learn this pairing: short gastric vessels = risk to gastric fundus; splenic hilum / lienorenal ligament = risk to tail of pancreas.
Blood supply
Arterial: the splenic artery is the largest branch of the coeliac trunk. It runs a characteristically tortuous course along the superior border of the pancreas before entering the lienorenal ligament and dividing at the hilum. Its tortuosity is a recognisable radiological sign and a favourite SBA stem.
Branches en route:
- Pancreatic branches (including dorsal and great pancreatic arteries)
- Short gastric arteries to the gastric fundus
- Left gastroepiploic artery along the greater curvature
Venous: the splenic vein runs behind the body of the pancreas. The inferior mesenteric vein (IMV) drains into it. The splenic vein then joins the superior mesenteric vein (SMV) behind the neck of the pancreas to form the portal vein.
➡ This is why splenic vein thrombosis (e.g. from chronic pancreatitis) causes left-sided portal hypertension with isolated gastric varices — and why a pancreatic tail tumour can do the same.
Microanatomy and function
The spleen has two functional compartments:
| Compartment | Structure | Function |
|---|---|---|
| White pulp | Periarteriolar lymphoid sheaths (PALS, T cells) and germinal centres (B cells) around central arterioles | Immune surveillance; antibody production; response to blood-borne antigens |
| Red pulp | Cords of Billroth and venous sinusoids packed with macrophages | Filtration of blood; removal of senescent and abnormal RBCs |
The red pulp performs two key functions:
- Culling — destruction of damaged or aged erythrocytes
- Pitting — removal of inclusions (nuclear remnants, Heinz bodies, parasites) from otherwise viable RBCs
The spleen is part of the reticuloendothelial system and is a secondary lymphoid organ (primary lymphoid organs are the thymus and bone marrow). In adult life it does not perform haemopoiesis — this only returns in pathological extramedullary haemopoiesis (e.g. myelofibrosis).
Indications for splenectomy
- Trauma — most common indication; usually blunt trauma
- Haematological — hereditary spherocytosis, ITP refractory to medical therapy, autoimmune haemolytic anaemia
- Hypersplenism — symptomatic cytopenias
- Splenic abscess or cyst
- Hodgkin's lymphoma staging (historical; now largely replaced by imaging)
- Iatrogenic injury during left-sided abdominal surgery
Splenic trauma and the AAST grading
The spleen is the most commonly injured solid abdominal organ in blunt trauma. The AAST (American Association for the Surgery of Trauma) grading is I–V, based on haematoma size, laceration depth, and vascular involvement (grade V = shattered spleen or hilar vascular injury devascularising the spleen).
Modern management is selective:
- Haemodynamically stable ➡ non-operative management with serial imaging and observation
- Stable but ongoing bleeding / contrast blush on CT ➡ splenic artery embolisation
- Haemodynamically unstable ➡ splenectomy
Post-splenectomy blood film
Without splenic filtration, abnormal cells and inclusions accumulate in the peripheral blood. Classical findings:
- Howell–Jolly bodies — basophilic nuclear remnants (the single most iconic finding)
- Target cells (codocytes) — increased surface-area-to-volume ratio
- Pappenheimer bodies — iron-containing siderotic granules
- Heinz bodies — denatured haemoglobin
- Pitted (pocked) RBCs
Cell counts change in a predictable order:
1. Thrombocytosis first (within days; the spleen normally sequesters platelets)
2. Granulocytosis and reticulocytosis within weeks
3. Lymphocytosis and monocytosis later
👩⚕️ Thrombocytosis is the first post-splenectomy change. If it persists or rises above ~1000 × 10⁹/L, antiplatelet prophylaxis may be required to reduce thrombotic risk.
OPSI and prophylaxis
Overwhelming Post-Splenectomy Infection (OPSI) is a fulminant sepsis with mortality up to 50%. The asplenic patient cannot opsonise encapsulated organisms, so these dominate:
- Streptococcus pneumoniae (most common)
- Haemophilus influenzae type b
- Neisseria meningitidis
Risk is highest in the first 2 years post-splenectomy and in children, but persists for life.
Prophylaxis — a guaranteed exam favourite:
| Measure | Detail |
|---|---|
| Vaccination | Pneumococcal, Hib, meningococcal (ACWY + B), annual influenza. Ideally 2 weeks before elective splenectomy; if emergency, give 2 weeks after to allow immune response |
| Antibiotics | Lifelong (or at least 2–5 years) prophylactic penicillin V (or amoxicillin); erythromycin if penicillin-allergic |
| Patient education | Medical alert bracelet, splenectomy card, urgent medical review for any febrile illness, standby antibiotic course for travel |
Splenomegaly — causes by size
A useful exam framework. The spleen must roughly triple in size before it becomes palpable.
| Degree | Examples |
|---|---|
| Massive (>20 cm, crosses midline) | Chronic myeloid leukaemia (CML), myelofibrosis, malaria, kala-azar (visceral leishmaniasis), Gaucher's disease |
| Moderate | Lymphoma, other leukaemias, portal hypertension, haemolytic anaemias, storage diseases |
| Mild | Infections (EBV, infective endocarditis, viral hepatitis), connective tissue disease (RA — Felty's syndrome: RA + splenomegaly + neutropenia), early portal hypertension, ITP |
➡ If a question gives you a tropical travel history + massive splenomegaly, think malaria or kala-azar. If a UK patient with rheumatoid arthritis has neutropenia and splenomegaly, think Felty's syndrome.
[Image: MCQs banner]
Test yourself
Which statement about the normal adult spleen is true?
- ((Haemopoiesis occurs in normal adults::Adult haemopoiesis is confined to bone marrow; splenic haemopoiesis is pathological (myelofibrosis).))
- ((The spleen contains macrophages::☑️ Red pulp cords of Billroth and sinusoids are packed with macrophages that cull old RBCs.))
- ((The spleen is a primary lymphoid organ::Primary lymphoid organs are thymus and bone marrow; spleen is secondary.))
- ((The spleen contains medullary sinuses::Medullary sinuses belong to lymph nodes, not the spleen.))
Which structure is at greatest risk during splenectomy?
- ((Left kidney::Retroperitoneal and protected by Gerota's fascia.))
- ((Splenic flexure of colon::Inferior to the spleen but not at the hilum.))
- ((Tail of pancreas::☑️ Lies in the lienorenal ligament at the hilum; injury causes pancreatic fistula.))
- ((Left adrenal gland::Retroperitoneal, not in the operative field.))
👩⚕️ Pancreatic tail injury is the classic cause of post-splenectomy fistula and subphrenic collection.
A surgeon is ligating the splenic artery during splenectomy. Which structure is most at risk?
- ((Left kidney::Retroperitoneal, not at direct risk.))
- ((Stomach fundus::At risk during short gastric ligation, not at the splenic artery itself.))
- ((Tail of pancreas::☑️ The splenic artery runs along the superior border of the pancreas to the hilum.))
- ((Left crus of diaphragm::Not closely related to the splenic vessels.))
During ligation of the splenic hilum, which structure must be avoided?
- ((Stomach fundus::At risk during short gastric ligation, not hilar dissection.))
- ((Left adrenal gland::Not at the splenic hilum.))
- ((Tail of pancreas::☑️ Within the lienorenal ligament at the hilum; damage causes pancreatic leak.))
- ((Transverse colon::Inferior to the operative field.))
Which structure is at risk while ligating the short gastric vessels?
- ((Tail of pancreas::At risk at the hilum, not during short gastric ligation.))
- ((Left kidney::Not related to short gastric vessels.))
- ((Transverse colon::Not at direct risk during this step.))
- ((Fundus of stomach::☑️ Short gastric vessels run in the gastrosplenic ligament from spleen to fundus.))
👩⚕️ Two ligaments, two danger zones: gastrosplenic = fundus; lienorenal = tail of pancreas.
Which ligament contains the splenic artery, splenic vein and tail of pancreas?
- ((Greater omentum::Connects stomach to transverse colon; contains gastroepiploic vessels.))
- ((Lesser omentum::Hepatogastric and hepatoduodenal ligaments; portal triad runs in the latter.))
- ((Gastrocolic ligament::Part of the greater omentum between stomach and transverse colon.))
- ((Lienorenal ligament::☑️ Anchors spleen to posterior abdominal wall; contains splenic vessels and pancreatic tail.))
In elective splenectomy for hereditary spherocytosis, which structure must be divided to mobilise the spleen from the posterior abdominal wall?
- ((Lesser omentum::Connects stomach and duodenum to liver.))
- ((Phrenicocolic ligament::Supports the inferior pole but is not the posterior attachment.))
- ((Gastrosplenic ligament::Anterior attachment to stomach; not the posterior one.))
- ((Lienorenal ligament::☑️ Posterior attachment over the left kidney; must be divided to mobilise the spleen.))
Post-splenectomy, which blood component changes first?
- ((Platelets — thrombocytosis::☑️ Spleen normally sequesters platelets; count rises within days.))
- ((Platelets — thrombocytopenia::Opposite direction; platelets rise post-splenectomy.))
- ((Reticulocytes::Increase, but later than platelets.))
- ((Granulocytes::Rise within weeks; platelets are first.))
Which finding would be expected on a blood film a week after splenectomy for trauma?
- ((High platelet count::☑️ Thrombocytosis (often >500 × 10⁹/L) appears within days.))
- ((High basophils::Can occur but not the dominant finding.))
- ((Neutrophilia::Granulocytosis develops later than thrombocytosis.))
- ((Lymphocytosis::Lymphocyte and monocyte rises take weeks.))
Which of the following is NOT seen post-splenectomy?
- ((Low WBC count::☑️ WBC count rises post-splenectomy, it does not fall.))
- ((Basophilia::Recognised post-splenectomy change.))
- ((Target cells::Classic poikilocyte of hyposplenism.))
- ((Pappenheimer bodies::Iron-containing granules accumulate without splenic filtration.))
- ((Heinz bodies::Denatured haemoglobin inclusions normally removed by the spleen.))
A child has a peripheral blood film one week after splenectomy. Which finding is NOT expected?
- ((Howell–Jolly bodies::Nuclear remnants — the classic hyposplenic finding.))
- ((Basophilia::Recognised post-splenectomy change.))
- ((Decreased WBC::☑️ WBC count rises after splenectomy.))
- ((Pitted RBCs::Surface pitting fails without splenic filtration.))
👩⚕️ Memorise the order: platelets → granulocytes → reticulocytes → lymphocytes/monocytes.
In the normal spleen, macrophages are found mainly in which region?
- ((White pulp::Contains B and T lymphocytes (PALS and germinal centres).))
- ((Cortex::A lymph node term, not splenic.))
- ((Mantle zone::Part of the white pulp follicle.))
- ((Red pulp::☑️ Cords of Billroth and sinusoids house the macrophages.))
A tortuous vessel arising from the coeliac axis is identified on CT. Which structure does it help supply?
- ((Pancreatic head::Supplied by pancreaticoduodenal arteries.))
- ((Duodenum::Pancreaticoduodenal supply from coeliac and SMA.))
- ((Gastric fundus::☑️ The tortuous splenic artery gives short gastric branches to the fundus.))
- ((Transverse colon::Middle colic from SMA.))
The inferior mesenteric vein most commonly drains into which vessel?
- ((Superior mesenteric vein::An anatomical variant; not the commonest pattern.))
- ((Splenic vein::☑️ IMV most commonly joins the splenic vein behind the pancreas.))
- ((Portal vein::Splenic + SMV form the portal vein; IMV joins before this confluence.))
- ((Inferior vena cava::Portal, not systemic, drainage.))
- ((Hepatic vein::Drains liver into IVC; not part of portal inflow.))
👩⚕️ IMV → splenic vein → joins SMV behind pancreatic neck → portal vein.
A 25-year-old undergoes emergency splenectomy for trauma. When should pneumococcal vaccination ideally be given?
- ((At the time of surgery::Immune response is blunted by acute physiological stress.))
- ((1 week post-op::Earlier than the optimal window for antibody response.))
- ((2 weeks post-op::☑️ Allows mounting of a protective antibody response after emergency splenectomy.))
- ((6 months post-op::Unnecessarily delayed; risk of OPSI is highest early.))
👩⚕️ Elective splenectomy = vaccinate 2 weeks before. Emergency splenectomy = vaccinate 2 weeks after.
Which organisms are most responsible for OPSI?
- ((Gram-negative enterics::Cause intra-abdominal sepsis, not classic OPSI.))
- ((Anaerobes::Not the typical OPSI pathogens.))
- ((Encapsulated bacteria — pneumococcus, Hib, meningococcus::☑️ Opsonisation of capsules requires splenic function.))
- ((Atypical mycobacteria::Cause disease in cellular immunodeficiency, not asplenia.))
A 40-year-old with rheumatoid arthritis is found to have splenomegaly and neutropenia. What is the diagnosis?
- ((Caplan's syndrome::RA + pneumoconiotic lung nodules.))
- ((Sjögren's syndrome::Dry eyes and mouth in autoimmune disease.))
- ((Felty's syndrome::☑️ Triad of RA + splenomegaly + neutropenia.))
- ((Still's disease::Juvenile RA variant with systemic features.))
Revision summary
- Anatomy ➡ LUQ, intraperitoneal, ribs 9–11; 1, 3, 5, 7, 9, 11 rule.
- Ligaments ➡ Gastrosplenic (short gastric + left gastroepiploic) | Lienorenal (splenic artery + vein + tail of pancreas).
- Splenectomy danger zones ➡ short gastrics = fundus; hilum = tail of pancreas.
- Blood supply ➡ splenic artery (coeliac, tortuous, superior to pancreas); splenic vein joins SMV behind pancreatic neck → portal vein; IMV → splenic vein.
- Microanatomy ➡ White pulp (PALS + germinal centres, immune) | Red pulp (cords of Billroth, macrophages, culling + pitting).
- Trauma ➡ AAST I–V; stable → conservative; blush → embolisation; unstable → splenectomy.
- Post-splenectomy film ➡ Howell–Jolly, target cells, Pappenheimer, Heinz, pitted RBCs. Order: platelets → granulocytes → reticulocytes → lymphocytes.
- OPSI ➡ encapsulated organisms (S. pneumoniae, Hib, N. meningitidis). Vaccinate 2 weeks pre-op (elective) or 2 weeks post-op (emergency). Lifelong penicillin V + medical alert.
- Massive splenomegaly ➡ CML, myelofibrosis, malaria, kala-azar.
- Felty's ➡ RA + splenomegaly + neutropenia.