The normal spleen is usually not palpable but is tucked beneath and above the left costal margin, between the fundus of the stomach and the diaphragm, with its long axis parallel to and running along the course of the tenth rib. When it enlarges, its lower border moves downwards and medially towards the middle of the anterior margin of the left ribcage.
A medical history, including exposure to various infections which may cause splenomegaly, and eliciting symptoms such as night sweats or fever, is vital, followed by a meticulous physical examination.
Examination of the Spleen (Stanford Medicine 25)
Various methods of palpation have been described, bimanual palpation, ballottement, and examination from above and behind the patient’s left side. These are all aimed at detecting the excursion of the enlarged spleen below the left lower margin of the ribcage during expiration.
Percussion is also of help in this examination, including Nixon’s and Castell’s techniques, and percussion of Traube’s semilunar space which is found to be shifted to the right side by an enlarged spleen.
False-positive findings occur if the diaphragm is fixed and flattened, as may occur in chronic lung disease, as well as when the diaphragm moves through a larger-than-normal range with respiration. On the other hand, these methods may fail to detect splenomegaly if the patient is obese, has ascites, or if the ribcage is unusually narrow, or the diaphragm is higher than normal.
Plain radiographs are of use when they show the spleen against a background of gas in the fundus of the stomach and the splenic flexure of the colon. In such a case they may reliably show the presence of an enlarged spleen.
Ultrasound scanning is reliable, safe, quick and non-invasive, allowing an abnormal spleen to be detected with a high coefficient of sensitivity and specificity.
This technique relies on the use of nuclear isotopes and produces accurate images of the spleen provided the vascular supply and splenic capsule are intact. It is however more costly, time-consuming, and cumbersome in the facilities required. An advantage is its detection of aberrant or ectopic spleens.
Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) Scanning
These methods provide a sharp clear picture of the spleen, with the omental fat providing a plane of separation from the blood vessels at the hilum and the splenic capsule. They are not limited by the presence of the ribs or the gas in the bowel. They are, however, costly and require the patient to be transported to the scanning module and to lie immobile on it for the necessary time. They also expose the patient to ionizing radiation.
Once the diagnosis of splenomegaly is established, further investigations are needed to identify the etiology. These include several types of blood tests.
A complete blood count with a peripheral smear will show the number of each kind of blood cell, along with any abnormalities of form. This may be a clue to the presence of red cell or white cell disorders. Cytopenia in hypersplenism, high white cell counts in leukemias, and the presence of blood parasites in malaria or kala-azar are all helpful in determining the cause of splenic enlargement. Red cell fragility tests detect the presence of disorders like hereditary spherocytosis and other hemolytic anemias.
Blood culture may be necessary to rule out typhoid.
Liver function tests may show the presence of portal hypertension. Lymphoproliferative disorders will require a lymph node excision biopsy, while hematogenous conditions may need bone marrow aspiration or sometimes a bone marrow biopsy.
Further testing such as serum protein electrophoresis will depend on the specific findings in the physical examination, imaging and blood tests.
In cases where the cause of the enlargement is not identified, and the patient is asymptomatic, it may be prudent to recall the patient for re-evaluation every six months or so. In other cases, a partial resection of the spleen may be carried out for histopathological examination, to rule out a lymphoma of the spleen.