The spleen is an organ located in the upper left part of the abdomen, tucked behind the lower ribs and beneath the diaphragm. It is part of the lymphatic system and primarily functions to filter blood, removing old or damaged red blood cells and storing blood components. Ultrasound, or sonography, is a non-invasive imaging technique that uses high-frequency sound waves to create live pictures of the body’s internal soft tissues. Measuring the size of the spleen with this technology is a common procedure that helps medical professionals assess the organ’s condition.
Why the Spleen is Measured
The size of the spleen serves as a direct indicator of several underlying medical conditions, making measurement an important diagnostic step. Unlike many other organs, the spleen can change size considerably in response to disease, particularly when overworked. Physicians often request an ultrasound measurement when they suspect splenomegaly, the medical term for an enlarged spleen.
Enlargement can be triggered by issues including infections like infectious mononucleosis, cytomegalovirus, and malaria. The spleen may grow as it processes infectious agents or abnormal cells. Chronic liver conditions, such as cirrhosis, commonly cause the spleen to enlarge due to portal hypertension, where increased pressure in the liver’s blood vessels backs up blood into the spleen.
Blood disorders are another primary reason for measurement, as conditions like hemolytic anemia, leukemia, or lymphoma can cause the spleen to swell while it attempts to clear abnormal blood components. Evaluating the spleen’s size helps in diagnosing these conditions, monitoring their progression, and determining the effectiveness of treatments. Because a physical exam can sometimes be inaccurate in detecting mild enlargement, the ultrasound provides a precise, objective measurement for clinical use.
Steps for Ultrasound Measurement
The procedure for measuring the spleen begins with the patient lying on their back (supine) or slightly turned onto their right side (right lateral decubitus position). This positioning helps move the spleen closer to the body wall, improving visualization by the sound waves. A sonographer applies a specialized gel to the upper left abdomen and side, which eliminates air pockets and facilitates the transmission of high-frequency sound waves from the transducer into the body.
The transducer is usually placed between the ribs, often in the 8th to 10th intercostal space, using a coronal oblique view that aligns with the organ’s natural long axis. This approach is preferred because the ribs protect the spleen, making a direct subcostal view difficult. The most widely accepted measurement is the maximum cranio-caudal length, which is the distance from the superior pole to the inferior pole of the spleen.
To ensure the entire length is captured, the patient is often asked to take a deep breath and hold it temporarily. This deep inspiration pushes the spleen downward, allowing the sonographer to capture the full length of the organ on a single longitudinal image. Once the optimal image is frozen on the screen, electronic calipers are used to mark the two farthest points along the splenic axis, providing the maximum length in centimeters.
While length is the primary measurement, sonographers may also measure the width (medial-lateral) and thickness (anterior-posterior) of the spleen, typically taken at the hilum. These additional dimensions allow for the calculation of an estimated splenic volume using a formula, which can offer a more comprehensive assessment of the organ’s size. However, the maximum longitudinal length remains the most common and standardized metric used across clinical settings to screen for enlargement.
Understanding Spleen Size Results
Once the maximum longitudinal length is obtained, the resulting number is interpreted against established reference ranges. For most adults, a spleen length of 12 centimeters or less is considered within the normal range. Normal size can vary slightly depending on factors like the patient’s height, sex, and overall body size.
Measurements exceeding 12 centimeters are used as the threshold for defining splenomegaly, though some clinicians use a slightly higher cutoff, such as 13 or 14 centimeters for taller males. The degree of enlargement is often categorized to help guide clinical management and identify the severity of the underlying condition. A maximum length between 11 and 20 centimeters is categorized as moderate splenomegaly.
A measurement greater than 20 centimeters indicates severe splenomegaly, suggesting a more advanced disease process. When the ultrasound confirms an enlarged spleen, the numerical result provides evidence that the organ is dealing with an increased workload, such as filtering damaged blood cells or fighting a systemic infection. This objective measurement helps physicians correlate the spleen’s physical status with the patient’s symptoms and blood test results to determine the cause of the size change.