Chapter 14: Lymphangiography

INTRODUCTION

For decades, bipedal lymphangiography was the standard imaging test for nonsurgical assessment of the lymphatic system. At Stanford University (Stanford, CA), several thousands of lymphangiographies were performed over 20 to 25 years beginning in the 1960s.¹

The technique allows detection of enlarged lymph nodes in lymphadenopathy but may also demonstrate internal architectural derangements within normal-sized lymph nodes. It may further demonstrate the lymphatic origin of a known fluid collection as in cases with chylaskos, lymphocele, chylothorax, or lymphatic fistula. Using an iodinated glycerol ester (lipiodol) as a contrast agent, the technique has also been shown to induce granulomatous reactions at the site of lymphatic leakage and thereby may support its successful treatment.

ALTERNATIVE IMAGING TECHNIQUES

Because lymphangiography is invasive and technically challenging and requires an experienced investigator as well as a compliant patient, its application has continuously decreased with the introduction of cross-sectional imaging.¹

Today sonography often serves as a first test for depiction of lymph nodes.² Image characteristics, such as a rounded shape, loss of the hyperechoic hilus reflex, node enlargement, and an enhanced cortical Doppler signal from increased vascularity, have been shown to indicate malignancy.^3,4 As a drawback, sonography is investigator dependent, may be time consuming, interferes with bowel gas, and often fails to precisely specify the origin of a fluid collection.

Indirect lymphangiography by intradermal pump injection of nonionic, water-soluble, dimeric, hexaiodinated contrast agents has been proposed but did not find its way into clinical routine.^5,6

Lymphangioscintigraphy is valuable in the assessment of lymphedema and the detection of the sentinel node as the first tumor-draining lymph node in patients with melanoma and breast cancer.^{7,8,9,10,11,12,13,14,15,16,17,18}

With cross-sectional imaging being optimized and broadly available, criteria for computed tomography (CT) and magnetic resonance (MR) detection of lymph nodes and lymphadenopathy has been described.^{19,20,21,22,23} These techniques offer three-dimensional capabilities, depict both lymphatic structures and the surrounding tissues and organs, and may even allow visualization of lymphatic structures not depictable by pedal lymphangiography (e.g., hypogastric and mesenteric nodes). On the other hand, these techniques often do not allow precise evaluation of the origin of a fluid collection and its leakage site and furthermore have no direct therapeutic potential.

Because CT and standard MR imaging (MRI) mainly apply size criteria for the assessment of lymph nodes, both techniques fail to detect lymphatic micrometastases within normal-sized lymph nodes. Therefore, the intravenous (IV) application of ultrasmall particles of iron oxide (USPIO) has been investigated for MR lymphography.²⁴ These particles are absorbed by the reticuloendothelial system (RES), which leads to a signal loss in normal nodes in T2-weighted ...