The spleen is an organ located in the upper left abdomen, nestled just behind the stomach and beneath the rib cage. It is a soft, purplish, fist-sized organ that plays a part in maintaining overall blood health and supporting the body’s defenses.
The Spleen’s Vital Functions
The spleen acts as a specialized filter for the blood, recognizing and removing old, damaged, or abnormally shaped red blood cells. Blood cells must pass through a complex maze of narrow passages within the spleen; those that fail this “quality control” are broken down by large white blood cells called macrophages. The spleen also stores a reserve of blood, including red blood cells and platelets, which can be released in situations of sudden blood loss.
Beyond its role in blood filtration and storage, the spleen is a component of the lymphatic system and part of the body’s immune system. It identifies and removes unwelcome microorganisms, such as bacteria and viruses, from the bloodstream. The spleen also produces antibodies that help combat infection.
Blood Tests Indicating Spleen Health
Assessing spleen function often involves examining blood components that the spleen filters, stores, or affects. A common starting point is a Complete Blood Count (CBC), which measures red blood cells, white blood cells, and platelets. Abnormalities in these counts can indirectly suggest issues with spleen activity. For example, a reduced red blood cell count (anemia) or a low platelet count (thrombocytopenia) might indicate an overactive spleen.
A Peripheral Blood Smear provides a closer look at the shape and characteristics of individual blood cells under a microscope. The presence of specific red blood cell abnormalities can directly point to reduced splenic filtration. Howell-Jolly bodies, which are small, round remnants of DNA within red blood cells, are typically filtered out by a healthy spleen. Their appearance in the blood suggests absent or diminished spleen function. Acanthocytes, red blood cells with irregular, spiky projections, and pitted red blood cells, which have indentations, are other indicators of compromised splenic function.
A Reticulocyte Count measures the number of immature red blood cells. This count can reflect the bone marrow’s response to red blood cell destruction. Elevated reticulocytes might indicate that the bone marrow is working harder to replace red blood cells that are being prematurely removed, potentially by an overactive spleen.
Understanding Abnormal Test Results
Abnormalities in blood tests provide insights into spleen function. A low platelet count (thrombocytopenia) can occur if an enlarged spleen traps too many platelets. Conversely, a very high platelet count might be seen after spleen removal, as there is no longer an organ to regulate platelet numbers.
The appearance of Howell-Jolly bodies on a peripheral blood smear strongly indicates absent or significantly reduced spleen function (asplenia or hyposplenism). These DNA remnants persist because the spleen is not effectively filtering them out. Similarly, the presence of acanthocytes may suggest the spleen is struggling to remove these abnormally shaped cells, potentially leading to their destruction and anemia. Anemia, characterized by a low red blood cell count, can result from an overactive spleen (hypersplenism) that destroys red blood cells too quickly.
An enlarged spleen, or splenomegaly, can lead to various blood count changes, including anemia, low white blood cells (leukopenia), and low platelets. These changes occur due to increased sequestration and destruction of these cells.
When Spleen Function Assessment is Important
Assessing spleen function is important in several clinical scenarios. Individuals experiencing symptoms such as unexplained fatigue, recurrent infections, or pain in the upper left abdomen may require evaluation.
Known medical conditions that affect the spleen, such as sickle cell disease, liver disease (like cirrhosis), certain infections (e.g., mononucleosis), or some cancers, also prompt spleen function assessment. In these conditions, the spleen may become enlarged or its function compromised. Assessment is also crucial for patients who have undergone a splenectomy (spleen removal) or are being considered for such a procedure, to understand their altered immune status and blood cell regulation.