Splenomegaly

Key takeaways

Splenomegaly belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Splenomegaly to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Splenomegaly from memory before moving on to harder problems.

Reference excerpt

Splenomegaly is an enlargement of the spleen. The spleen usually lies in the left upper quadrant (LUQ) of the human abdomen. Splenomegaly is one of the four cardinal signs of hypersplenism which include: some reduction in number of circulating blood cells affecting granulocytes, erythrocytes or platelets in any combination; a compensatory proliferative response in the bone marrow; and the potential for correction of these abnormalities by splenectomy. Splenomegaly is usually associated with increased workload (such as in hemolytic anemias), which suggests that it is a response to hyperfunction. It is therefore not surprising that splenomegaly is associated with any disease process that involves abnormal red blood cells being destroyed in the spleen. Other common causes include congestion due to portal hypertension and infiltration by leukemias and lymphomas. Thus, the finding of an enlarged spleen, along with caput medusae, is an important sign of portal hypertension.

Definition

The standard system for classifying splenomegaly on radiography is:

Normal (not splenomegaly): the largest dimension is less than 11 cm Moderate splenomegaly: the largest dimension is between 11 and 20 cm Severe splenomegaly: the largest dimension is greater than 20 cm Also, a cutoff of a craniocaudal height of 13 cm is also used to define splenomegaly. In addition, individual intervals have been established:

For children, the cutoffs for splenomegaly are given in this table, when measuring the greatest length of the spleen between its dome and its tip, in the coronal plane through its hilum while breathing quietly. At autopsy, splenomegaly can be defined as a spleen weight above the upper limit of the standard reference range of 230 g (8.1 oz). Splenomegaly refers strictly to spleen enlargement, and is distinct from hypersplenism, which connotes overactive function by a spleen of any size. Splenomegaly and hypersplenism should not be confused. Each may be found separately, or they may coexist. Clinically, if a spleen is palpable (felt via external examination), it means it is enlarged as it has to undergo at least twofold enlargement to become palpable. However, the tip of the spleen may be palpable in a newborn baby up to three months of age.

Signs and symptoms Symptoms may include abdominal pain, chest pain, chest pain similar to pleuritic pain when stomach, bladder or bowels are full, back pain, early satiety due to splenic encroachment, or the symptoms of anemia due to accompanying cytopenia. Signs of splenomegaly may include a palpable left upper quadrant abdominal mass or splenic rub. It can be detected on physical examination by using Castell's sign, Traube's space percussion or Nixon's sign, but an ultrasound can be used to confirm diagnosis. In patients where the likelihood of splenomegaly is high, the physical exam is not sufficiently sensitive to detect it; abdominal imaging is indicated in such patients. In cases of infectious mononucleosis splenomegaly is a common symptom and health care providers may consider using abdominal ultrasonography to get insight into a person's condition. However, because spleen size varies greatly, ultrasonography is not a valid technique for assessing spleen enlargement and should not be used in typical circumstances or to make routine decisions about fitness for playing sports.

Causes The most common causes of splenomegaly in developed countries are infectious mononucleosis, thalassemia, splenic infiltration with cancer cells from a hematological malignancy and portal hypertension (most commonly secondary to liver disease, and sarcoidosis). Splenomegaly may also come from bacterial infections, such as syphilis or an infection of the heart's inner lining (endocarditis). Splenomegaly also occurs in mammals parasitized by Cuterebra fontinella. The possible causes of moderate splenomegaly (spleen <1000 g) are many, and include:

The causes of massive splenomegaly (spleen >1000 g) are

chronic myelogenous leukemia myelofibrosis malaria splenic marginal zone lymphoma

Pathophysiology Splenomegaly can be classified based on its pathophysiologic mechanism:

Congestive, by pooled blood (e.g., portal hypertension) Infiltrative, by invasion by cells foreign to the splenic environment (e.g., metastases, myeloid neoplasms, lipid storage diseases) Immune, by an increase in immunologic activity and subsequent hyperplasia (e.g., endocarditis, sarcoidosis, rheumatoid arthritis) Neoplastic, when resident immune cells originate a neoplasm (e.g., lymphoma).

Diagnosis Abdominal CT is the most accurate. The spleen needs to be 2–3 times larger than normal to be palpable below the costal margin in physical examination.

Treatment If the splenomegaly underlies hypersplenism, a splenectomy is indicated and will correct the hypersplenism. However, the underlying cause of the hypersplenism will most likely remain; consequently, a thorough diagnostic workup is still indicated, as, leukemia, lymphoma and other serious disorders can cause hypersplenism and splenomegaly. After splenectomy, however, patients have an increased risk for infectious diseases. Patients undergoing splenectomy should be vaccinated against Haemophilus influenzae, Streptococcus pneumoniae, and Meningococcus. They should also receive annual influenza vaccinations. Long-term prophylactic antibiotics may be given in certain cases.

As an adaptation An enlarged spleen may be an inherited, adaptive trait selected in populations that need extra oxygen carry capacity such as deep sea divers. The Sama-Bajau people, notable for free-diving, have spleens that are 50% larger than those of nearby ethnic groups.

Illustrations

Splenomegaly: Normal spleen (in green) — Normal spleen (in green)

Worked examples

Example 1 — a first encounter with Splenomegaly

Start with the simplest possible case. Write down what Splenomegaly 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 Splenomegaly 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 Splenomegaly 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 Splenomegaly

In research: Splenomegaly 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 Splenomegaly 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: Splenomegaly is common in secondary-school and first-year university syllabi. It links to neighbouring topics Diseases of spleen, Symptoms and signs: Digestive system and abdomen, so understanding it makes those chapters shorter.
In everyday life: Look for Splenomegaly 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.

How to study Splenomegaly in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Splenomegaly means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Splenomegaly out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Splenomegaly in simple terms?

Splenomegaly is an enlargement of the spleen. The spleen usually lies in the left upper quadrant (LUQ) of the human abdomen.

Why does Splenomegaly 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 Splenomegaly?

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 Splenomegaly.