What is the spleen?
Spleen is a lymphoid organ with a size of a hand fist, similar in structure to a lymph node and it is an important part of lymphatic and immune systems. The spleen lies behind the stomach in the left upper part of the abdomen which is medically called the upper left hypochondrium. The human spleen weighs approximately 6 ounces (170 grams) and it is covered with a dense fibroelastic tissue called the splenic capsule. The splenic capsule is semi-translucent letting the spleen express its reddish-purple color.
Function of spleen
Spleen carries out a lot of important immunological and hematological tasks, yet it is not essential and humans can live without it. Functions of the spleen include the following:
- Spleen is believed to be a reservoir sac of blood as storage of blood is a characteristic function of the spleen. Spleen normally stores up to 240 ml of red blood cells. In case of bleeding or hypovolemia spleen squeeze itself to pour blood into the circulation to compensate for what is lost.
- The spleen is where some white blood cells are matured and activated, therefore if the spleen is excised or damaged the patient will be more susceptible to getting an infection. Circulating macrophages are hosted in the spleen to get rid of microbes. Spleen also contains macrophage in its own tissue to recognize and phagocytose microorganisms.
- Spleen is considered a large lymph node because it acts as a station in which blood is filtered from many pathogens. Spleen also clears the body from tissue debris and cellular wastes especially mal-formed red blood cells. Worn red blood cells with degraded hemoglobin lose their iron content in the spleen to be released in the bloodstream to contribute to forming new RBCs. Patients with damaged spleen lose the privilege of quality controlling red blood cells.
What is splenomegaly?
Splenomegaly is a common medical condition in which the spleen is enlarged in size or weight. The hypertrophied spleen resulted from acute or chronic overload on the spleen which is caused by a wide variety of diseases. The largest dimension of the spleen doesn’t normally exceed 11 cm whereas in splenomegaly it may reach up to 25 cm. Surgeons may also consider spleens weighing more than 400 grams as splenomegaly. Splenomegaly is a serious medical condition that may cause potentially fatal complications such as splenic rupture thus patients should seek medical attention if they suspect an enlargement in their spleen.
Statistics of splenomegaly
Splenomegaly is a well-known medical condition worldwide yet it is more defined as a tropical disorder that is more common in Asia, Africa, and South America than in Europe and North America. Since splenomegaly is a chronic condition that may need negligence of the underlying cause, then it is more prevalent in developing regions. A study showed that the incidence rate of splenomegaly in the USA is 2% which is mainly resulted from hematological causes. The mortality rate of splenomegaly is considerable as patients who have uncontrolled splenomegaly are exposed to the risk of a 1.8% death rate within 30 days.
Degrees of splenomegaly
Splenomegaly is classified according to its degree of enlargement based on clinical physical examination or radiology. Physicians could classify splenomegaly roughly into mild, moderate, and severe depending on the length of the longest dimension. Length of the longest dimension in mild splenomegaly 11-15 cm, moderate splenomegaly 16-20 cm while severe splenomegaly is more than 20 cm.
Hackett’s grading system is a more specific tool to classify splenomegaly into 5 grades. Grade 1 is the mildest form of splenomegaly in which the spleen is barely palpated on deep inspiration. Grade 2 includes spleen enlargement and extension downward and toward the midline to be midway between the umbilicus and the costal margin (lower border of the ribs). Grade 3 includes further enlargement of the spleen. Grade four is characterized by spleen enlargement to reach the umbilicus. Grade 5 is the most severe and life-threatening form of splenomegaly in which the spleen extends beyond the umbilicus toward symphysis pubis.
» Now, let’s discuss causes, diagnosis, symptoms and treatment options of splenomegaly
Causes of splenomegaly
The etiology of splenomegaly includes a wide variety of diseases. Almost all causes of the enlarged spleen are due to systemic disorders that affect organs of multiple systems. We will summarize the most common causes of splenomegaly into:
1- Infection is the most common cause of enlarged spleen. Spleen, as mentioned, is a lymphoid organ that plays an immunological role therefore infections may result in splenomegaly. Splenomegaly is caused by infection with different microorganisms. Viral infection such as mononucleosis which is caused by the Epstein bar virus is believed to cause splenomegaly.
Parasitic infections with toxoplasma and malaria are found to cause splenomegaly, particularly in developing countries. Kala-azar which is a type of tropical leishmaniasis is believed to be one of the most common causes of severe splenomegaly.
Acute typhoid infection is considered the most common bacterial infection causing splenomegaly. Syphilis and TB (tuberculosis) are also examples of bacterial infections that may cause spleen enlargement. Spleen abscess is one of the most serious causes of enlarged spleen, yet patients with spleen abscess usually complain first from splenic throbbing pain and fever.
2- Liver diseases are a well-known cause of splenomegaly. Spleen is connected with the liver by a splenic vein which takes part in forming a portal vein that pours in the liver. Diseases affecting the function of the liver such as liver cirrhosis or liver cell failure will subsequently affect the spleen drainage system leading to spleen congestion and enlargement.
3- Heart failure whether RSHF (right-sided heart failure) or congested heart failure will mostly cause splenomegaly as a part of systemic venous congestion.
4- Hemolytic anemia is a type of anemia characterized by an increased rate of RBCs destruction (hemolysis). Over loading, the spleen with many destroyed red blood cells forces it to be more functioning consequently larger in size. Other hematological disorders such as polycythemia, thalassemia, and spherocytosis could be presented with splenomegaly.
5- Malignancy is less common to primary develop in the spleen but it is often metastasis from a tumor of another organ that circulates in the blood to settle in the spleen to be called a secondary tumor. Spleen secondary tumor grows and proliferates into spleen tissue causing splenomegaly. Leukemia, malignancy of the blood-forming tissue in the bone marrow is documented to cause splenomegaly due to disturbance in the differentiation, maturity, and morphology of the blood cells.
6- Decreased flow (stasis) of the spleen venous drainage, as well as lymphatic drainage, could cause splenomegaly. Splenic venous stasis may be caused by portal hypertension, hepatic vein obstruction, and splenic vein obstruction.
7- Other causes of splenomegaly include sarcoidosis, rheumatic arthritis (felty syndrome), systemic lupus, amyloidosis, and collagen vascular diseases.
8- Idiopathic splenomegaly is defined as splenomegaly of unknown cause which is usually diagnosed by exclusion of the previously mentioned causes.
Diagnosis and How to evaluate the degree of splenomegaly?
Doctors usually can palpate enlarged spleens and evaluate their enlargement, yet other modalities are applicable to detect and assess splenomegaly.
Ultrasound could be used to detect splenomegaly particularly for obese and pregnant patients as it is safe, available, and non-invasive. CT (computerized tomography) is also a useful tool to detect the volume of the spleen. However, it is often done before operations.
MRI provides excellent and detailed images of soft tissues including the spleen but it is rarely done to diagnose splenomegaly due to the availability of simpler options. A PET scan is used if spleen lymphoma is suspected. If a lump or abnormal mass is found in imaging of the spleen, a biopsy of the spleen may be necessary to figure it out.
Blood tests may be helpful in detecting the underlying cause of splenomegaly and in evaluating the progress after treatment. Liver function test (LFT), CRP, ESR aren’t specific tests for splenomegaly but it reflects the activity of the underlying disease. CBC may also indicate the source of infection whether bacterial, viral, or parasitic.
Symptoms
Although mild splenomegaly could be asymptomatic, it is usually presented with abdominal pain as patients’ complaints include vague pain in the upper left abdomen that may refer to the left shoulder. Spleen enlargement cause stretching of the splenic capsule which stimuli pain receptors. In some patients, pain may increase with deep inspiration or after heavy meals.
Splenomegaly is often associated with anemia so patients may be pale. Hemolytic jaundice (yellowish discoloration of the skin and sclera) is a medical condition in which there is a high rate of RBCs destruction and it is commonly seen in a patient with splenomegaly. Patients with splenomegaly may also complain of fatigue, malaise, and fever in case of infection.
Fate
Splenomegaly is currently a controllable condition and usually has a good prognosis, yet complications may occur if neglected. The mortality rate of splenomegaly may change according to its severity and patients’ medical condition but overall it is almost considerable. Recent statistics have shown that 20% of non-managed cases of splenomegaly develop complications.
The severity of splenomegaly is directly proportional to its risk of complication. Spleen rupture and recurrent infections are the most serious complication of splenomegaly that may be life-threatening, apart from that splenomegaly is limited to the previously mentioned symptoms.
Similar disorders
Hepatosplenomegaly (HSM) is a medical condition that includes swelling and enlargement of both the liver and spleen. HSM is similar to a great extent to splenomegaly in causes, symptoms, and investigations but it is often more serious.
Many people may get confused between splenomegaly and hypersplenism. Hypersplenism is a functional disorder of the spleen in which the spleen is overactive and functioning more than normal regardless of its size while splenomegaly’s main criterion is spleen enlargement.
What is the treatment of splenomegaly?
Treatment of splenomegaly mainly depends on treating the underlying cause. For instance, a viral infection complicated with splenomegaly is firstly managed by giving anti-virals. Mild to moderate splenomegaly usually respond well to medical treatment.
Splenomegaly is usually associated with other systems affections, so patients are preferred to be monitored while being treated to avoid unexpected side effects. Physicians believe that patients with splenomegaly may be immune-compromised so they prescribe short-term broad-spectrum antibiotics to prevent secondary bacterial infection.
Splenectomy (spleen removal surgery)
Physicians have to assess the grade of splenomegaly before starting treatment because a severe form of splenomegaly is an indication for splenectomy. Splenectomy is a major surgical operation in which the surgeon partially or completely removes the spleen. The success rate of splenectomy is reasonable as it is estimated to be about 60%, on the other hand, the splenectomy mortality rate is relatively low (1.5%). Statistics have shown that life expectancy for patients who had splenectomy isn’t affected however their quality of life has improved.
Splenectomy is indicated in critical cases that require surgical interference otherwise the patients will suffer from potentially fatal complications. Indications of splenectomy are:
- Massive splenomegaly that is suspected to rupture is an urgent call for surgical removal of the spleen
- Primary tumors of the spleen aren’t commonly reported but if so doctors will prefer to surgically excise the tumor or the whole spleen. Spleen isn’t an essential organ for humans moreover, high vascularity of the spleen makes tumors spread easier therefore physicians recommend its removal once spleen tumor is found.
- A life-threatening spleen abscess or even not responding to antibiotics is an indication for splenectomy to avoid septicemia.
- Spleen rupture is a serious emergency that requires immediate medical care. Fortunately mild to moderate spleen rupture could be controlled well. Internal bleeding caused by a ruptured spleen is the main cause of death
Postoperative instructions for patients who had splenectomy include long-term oral penicillin intake, avoiding straining, avoiding infections as possible, avoiding traveling to endemic countries, and informing your doctor in case of fever. Physicians usually recommend vaccination against pneumococci, meningococci, and homophiles influenza two weeks after surgery.
Complications of splenectomy
Splenectomy has recently become safer with minimal risks. Complications of spleen removal are usually post-operative and involve infection due to reduced immunity. Streptococcus pneumonia and Haemophilus influenza are believed to be the most common infections affecting patients who underwent splenectomy. Hernia is reported as a complication of many surgeries including splenectomy so patients are advised to avoid straining. Intraoperative complications of splenectomy such as injury of the pancreas and stomach aren’t common.