Lymphoscintigraphy for Lymphedema

74-296 MBq of ^99mTc with filtered (smaller than 22 microns) sulfur colloid particles suspended in 0.10 mL of saline is injected into the dorsum of the hand or foot or between the digits. The area is massaged for 2 minutes. Dynamic and delayed images (up to 4 hours) are obtained.

Lymphedema can be classified as primary and secondary. Primary lymphedema usually affects younger patients without a history of trauma or radiation and may be unilateral or bilateral. Secondary lymphedema in the developed world is often the result of trauma (iatrogenic or otherwise) or radiation therapy. In developing countries, infectious causes (e.g., filariasis) are common.

Contrary to what is found in Mettler and Guiberteau's book (5th ed), it is now thought that primary and secondary lymphedema cannot be reliably differentiated from each other based on lymphoscintigraphy alone.

Abnormal findings on lymphoscintigraphy include:

• Decreased numbers of non-obstructed lymphatic channels
• Lack of migration of radiotracer from the injection site
• Slow transport from injection site
• Decreased numbers of visualized lymph nodes
• Diffuse dermal activity
• Multiple tortuous collateral channels

Clinical mimickers of lymphedema include

• Obesity
• Venous disease
• Systemic disease (e.g., hypoproteinemia)

References

Moshiri M, Katz DS, Boris M, Yung E. Using lymphoscintigraphy to evaluate suspected lymphedema of the extremities. AJR Am J Roentgenol. 2002 Feb;178(2):405-12.