Liver and spleen imaging

Liver-spleen imaging, also known as a reticuloendothelial system (RES) scan, is a type of nuclear medicine test used to evaluate the function and anatomy of the liver and spleen. It helps identify various functional abnormalities associated with the reticuloendothelial cells, which are part of the body's immune system and are heavily concentrated in these organs.  This test involves the use of a small dose of radiopharmaceutical, typically Technetium-99m sulfur colloid, which is taken up by healthy liver and spleen tissues. By observing how this tracer distributes within these organs, physicians can assess tissue function, organ size, shape, and pathological changes such as nodules, infarcts, or abnormal uptake patterns.

The liver-spleen scan is particularly helpful in conditions where liver disease is suspected or being monitored, and it also helps differentiate between certain types of liver lesions such as focal nodular hyperplasia (FNH) and malignant liver tumors.

What is Liver-Spleen Imaging?

1. Liver-spleen imaging is a functional nuclear scan performed to assess the health and function of reticuloendothelial cells within the liver and spleen.
2. It uses Technetium-99m (Tc-99m) sulfur colloid, a tracer that is naturally taken up by the liver and spleen’s filtering cells.
3. A gamma camera is used to capture images showing how the tracer distributes, helping detect functional defects, organ size discrepancies, and abnormal tissue activity.

Clinical Indications for Liver-Spleen Scan

This scan is recommended in a wide variety of clinical situations where the structure or function of the liver and spleen needs to be evaluated:

• Suspected focal nodular hyperplasia (FNH)
• Evaluation of cirrhosis or chronic liver disease
• Detection of hepatocellular carcinoma or metastatic liver lesions
•  Assessment of splenic infarction or accessory spleens
• Investigation of hepatosplenomegaly (enlarged liver and spleen)
• Evaluation of portal hypertension
• Confirmation of liver lobe abnormalities or resectability before surgery
• Detection of post-traumatic splenic rupture or functional asplenia
• Differentiation between benign and malignant liver lesions

How is Liver-Spleen Imaging Performed?

The procedure is simple, safe, and typically completed within an hour:

1. A radiotracer (99mTc sulfur colloid) is injected into a vein in the arm.
2. The patient is then asked to lie on a table under a gamma camera that will capture images of the liver and spleen.
3. Imaging usually begins about 10–15 minutes after injection and lasts for 30–45 minutes.
4. The patient may be asked to change positions to capture multiple views of the organs.
5. There is no need for sedation, and the patient can resume normal activities shortly after the scan.

Comparison with Other Liver Imaging Modalities 

While liver-spleen imaging is functional, modalities like ultrasound, CT scan, and MRI offer structural imaging:

• Ultrasound is commonly used for the initial assessment of liver size and texture but cannot assess the function of liver cells.
• CT scan provides detailed anatomical images and is excellent for detecting mass lesions, but it may miss functional changes in early disease.
• MRI is highly sensitive in soft tissue characterization but may not differentiate between FNH and malignant tumors based on function.
• Liver-spleen scan, in contrast, evaluates how liver and spleen cells function and take up the tracer. For example, focal nodular hyperplasia shows normal or increased uptake, while malignant lesions show cold spots (areas of no tracer uptake), helping in differentiation.

This functional aspect is the key differentiator—liver-spleen imaging can detect functional defects even before anatomical abnormalities appear, making it particularly useful in early-stage liver disease and differentiation of benign vs malignant masses.

Understanding the Reticuloendothelial System (RES)

The reticuloendothelial system is a network of cells that filter and remove foreign substances, cellular debris, and microbes from the blood. It is primarily located in the:

• Liver (Kupffer cells) – act as immune sentinels in liver sinusoids
• Spleen (macrophages) – filter damaged blood cells and pathogens
• Bone marrow – involved in immune and hematopoietic function

Liver-spleen imaging provides direct insight into the functionality of these RES cells, helping assess immune activity and organ integrity.

What the Scan Can Reveal

1. Hepatic dysfunction – Areas of reduced or absent uptake indicate poor liver cell function, often due to cirrhosis or malignancy.
2. Focal lesions – Cold areas (no uptake) suggest tumors or abscesses; warm areas may suggest FNH.
3. Splenic abnormalities – Accessory spleens or infarcts appear as unexpected tracer accumulation or defects.
4. Portal hypertension – Seen as colloid shift to bone marrow or lungs due to reduced liver uptake.
5. Post-surgical assessment – Can confirm successful splenectomy or detect residual splenic tissue.

Advantages of Liver-Spleen Imaging

• Functional evaluation of liver and spleen activity
• Helps differentiate FNH from hepatic malignancy
• Non-invasive, safe, and minimal radiation exposure
• Can detect accessory spleens or splenic infarcts
• Useful in early detection of liver disease before structural damage
• Effective in monitoring progression or response to treatment
• Aids in surgical planning and evaluation of post-trauma injuries

Limitations

1. Not ideal for detailed structural imaging—CT/MRI may be needed for precise anatomical localization.
2. May not detect very small lesions or early-stage tumors without functional alteration.
3. Cannot replace biopsy or histological diagnosis in suspicious lesions.
4. Accuracy may be limited if patient has impaired RES function or recent nuclear studies.

Safety and Side Effects

Liver-spleen imaging is extremely safe:

• Uses a low-dose radiopharmaceutical
• No sedation or hospitalization required
•  Rare allergic reactions or complications
•  Suitable for children and elderly patients

However, pregnant or breastfeeding women should consult their physician before undergoing the test. findings.