Splenomegaly is defined as enlargement of the spleen measured by size or weight. The spleen plays a significant role in hematopoiesis and immunosurveillance. The major functions of the spleen include clearance of abnormal erythrocytes, removal of microorganisms and antigens as well as the synthesis of immunoglobulin G (IgG). The spleen also synthesizes the immune system peptides properdin and tuftsin. Also, approximately one-third of circulating platelets are stored in the spleen. The normal position of the spleen is within the peritoneal cavity in the left upper quadrant adjacent to ribs nine through 12. The normal sized spleen abuts the stomach, colon, and left kidney A normally sized spleen measures up to 11 cm in craniocaudal length. A length of 11 cm to 20 cm indicates splenomegaly, and a length greater than 20 cm is definitive of massive splenomegaly. The normal weight of the adult spleen is 70 g to 200 g, spleen weight of 400 g to 500 g indicates splenomegaly and spleen weight greater than 1000 g is definitive of massive splenomegaly. The normal sized spleen is usually not palpable in adults. However, it may be palpable due to variations in body habitus and chest wall anatomy. Splenomegaly may be diagnosed clinically or radiographically using ultrasound, CT imaging, or MRI. Splenomegaly may be a transient condition due to acute illness or may be due to serious underlying acute or chronic pathology.
The most common causes of splenomegaly include:
The mechanism underlying splenic enlargement varies based on the etiology. In the case of acute infectious illness, the spleen performs increased work in clearing antigens and producing antibodies and increases the number of reticuloendothelial cells contained within the spleen. These increased immune functions may result in splenic hyperplasia. In the case of liver disease and congestion, underlying illness causes increased venous pressure causing congestive splenomegaly. Extramedullary hematopoiesis exhibited in myeloproliferative disorders can lead to splenic enlargement (infiltrative splenomegaly).
Splenic sequestration crisis (SSC) is a life-threatening illness common in pediatric patients with homozygous sickle cell disease and beta thalassemia. Up to 30% of these children may develop SSC with a mortality rate of up to 15%. This crisis occurs when splenic vaso-occlusion causes a large percentage of total blood volume to become trapped within the spleen. Clinical signs include severe, rapid drop in hemoglobin leading to hypovolemic shock and death. Pediatric patients with sickle cell disease and beta thalassemia experience multiple splenic infarcts, resulting in splenic fibrosis and scarring. Over time, this leads to a small, auto infarcted spleen typically by the time patients reach adulthood. Splenic sequestration crisis can only occur in functioning spleens which may be why this crisis is rarely seen in adults. However, late adolescent or adult patients in this group who maintain splenic function may develop splenic sequestration crisis.
Splenomegaly is a rare condition, with an estimated prevalence of approximately 2% of the total United States population. In adults, there has been no reported predominance in prevalence based on ethnicity, gender, or age.
Splenomegaly can be classified based on its pathophysiologic mechanism:
The most common physical symptom associated with splenomegaly is vague abdominal discomfort. Patients may complain of pain in the left upper abdomen or referred pain in the left shoulder. Abdominal bloating, distended abdomen, anorexia, and/or early satiety may also occur. Commonly, patients will present with symptoms due to the underlying illness causing splenomegaly. Constitutional symptoms such as weakness, weight loss, and night sweats suggest malignant illness. Patients with splenomegaly due to acute infection may present with fever, rigors, generalized malaise, or focal infectious symptoms. Patients with underlying liver disease may present with symptoms related to alcohol abuse or hepatitis. Symptoms of anemia (lightheadedness, dyspnea, or exertion), easy bruising, bleeding, or petechiae may indicate splenomegaly due to underlying hemolytic process.
Physical examination of the spleen is performed with the patient in supine and right lateral decubitus position with neck, hips, and knees flexed. This positioning relaxes abdominal wall musculature and rotates the spleen to a more anteriorly. Light fingertip pressure is applied below the left costal margin during deep inspiration. The examiner may feel the rounded edge of the spleen pass underneath the fingertips at maximum inspiration and then received with expiration. The exam is abnormal if the spleen is palpated more than 2 cm below the costal margin. In massive splenomegaly, the spleen may be palpated deep into the abdomen, crossing the midline of the abdomen and may even extend into the pelvis. Studies have shown that normal sized spleens may be palpable in approximately 3% of adults.
Patients may have an abnormally palpable spleen with or without exam findings of contributing underlying illness. Patients with splenomegaly due to acute infection may have exam findings consistent with infectious mononucleosis, endocarditis, or malaria. Exam findings of petechiae, abnormal mucosal bleeding, or pallor may accompany hematologic diseases. Jaundice, hepatomegaly, ascites, or spider angiomata may be present in patients with liver disease. Patients with rheumatologic diseases may present with joint tenderness, swelling, rash, or an abnormal lung exam.
A combination of serum testing and imaging studies may definitively diagnose splenomegaly and the underlying cause. Derangement in the complete blood (cell) counts and morphology including WBC, RBC, and platelets will vary based on underlying disease state. Abnormalities in liver function tests, lipase, rheumatologic panels, and disease-specific infectious testing aid in the diagnosis of causative disease.
Imaging may be used to diagnose splenomegaly and elucidate its underlying cause. The spleen has a similar attenuation as the liver when measured on CT imaging. In addition to diagnosing splenomegaly (splenic measurement of greater than 10 cm in craniocaudal length), abdominal CT may detect splenic abscess, mass lesions, vascular abnormalities, cysts, inflammatory changes, traumatic injury, intra-abdominal lymphadenopathy, or liver abnormalities.
Ultrasound is a useful imaging modality in measuring the spleen and spares the patient radiation from CT imaging. Normal spleen size measured via ultrasound is less than 13 cm superior to the inferior axis, 6 cm to 7 cm in medial to lateral axis and 5 cm to 6 cm in anterior to posterior plane.
MRI, PET scans, liver-spleen colloid scanning, and splenectomy and splenic biopsy may be indicated in certain cases.
Treatment of splenomegaly is targeted at treating the underlying disease and protecting the patient from complications of splenomegaly itself. Patients with splenomegaly from any cause are at increased risk of splenic rupture, and increased attention must be made to protect the patient from abdominal trauma. Treatment ranges from abdominal injury avoidance in the young healthy patient with splenomegaly due to infectious mononucleosis, to splenectomy of a massively enlarged spleen in a patient with Hairy cell leukemia. Likewise, the prognosis is largely dependent on underlying disease state.
Patients who undergo splenectomy are at increased risk of overwhelming infection due to encapsulated organisms such as Haemophilus Influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. They should receive vaccinations against these organisms. Careful attention must be paid to post-splenectomy patients presenting with febrile illnesses as they may require more aggressive, empiric antibiotic therapy.