Infection, trauma, insect bites, and chronic venous disease are other causes of secondary lymphedema. The occurrence of lymphedema positively correlates with the increased number of resected nodes and irradiation as well as the extent of the operative procedure or tissue damage from other inciting agents. Appearance time of lymphedema is highly variable from months, years, to even decades later. This prolonged delay in appearance probably reflects vigorous lymphatic collateral for­mation, which gradually succumbs to progressive valve incompetence associated with lymphatic hypertension and fibrotic changes in the obstructed trunks along with associated soft tissue alterations. Lymphatic pumping gradually fails over time because of unremitting or escalating resistance to lymphatic flow.

Among the rarer lymphatic disorders are chylous reflux syndromes (Fig. 19.2j), where intestinal lymph flows retrograde through incompetent lymphatic valves and accumu­lates in various organs, other body parts, and tissues or leaks to the outside. There are congenital forms, which may be generalized as in neonatal chyledema, from defective lymphatic growth and valve formation, or acquired from functional or anatomical obstruction (e.g., lymphatic filariasis) or traumatic disruption of the thoracic duct, cis­terna chyli, or their tributaries; or indeterminate (as in lymphangioleiomyomatosis).

Chylous syndromes often present substantial challenges in defining the nature and location of the structural or functional abnormalities. Understanding the lym­phodynamic events and treating the condition through non-operative and operative means is imperative. Radionuclide WB-LAS represents a major advance in non­invasively documenting the structural and lymphodynamic aspects of chylous reflux syndromes and providing documentation of the effectiveness of therapeutic inter­ventions designed to reduce, divert, or eliminate the chylous reflux.

In contrast to secondary lymphedema in developed countries, acquired lym­phedema in less developed or third-world countries is often caused by filariasis or other infectious processes. Transmitted in larval form by insect vectors, the adult filarial nematode takes up residence in the peripheral lymphatic vessels and nodes. Seemingly impervious to the host defense mechanisms (lymph nodes, lymphocytes, circulating lymph) or else confounding them by molecular mim­icry, the active adult worms interfere with lymph flow, and in extreme cases, the involved limbs or genitalia take on an elephantine or pachyderm appearance. Some patients have predominant or concomitant visceral lymphatic involvement, which may culminate in conditions such as chyluria, hydrocele, chylous reflux (chylometrorrhagia or chylous vesicles), genital edema, or even massive breast engorgement.7 Because many patients in endemic areas often walk barefoot, it is thought that overt or subclinical bacterial infection contributes to the grotesque deformities often associated with these parasitic conditions. WB-LAS vividly depicts a full range of lymphatic structural and functional abnormalities in this condition (Fig. 19.4).

The Klippel–Trenaunay (KT) vascular birthmarks syndrome is often associated with venous Klippel–Trenaunay–Servelle syndrome. Lymphatic abnormalities occasionally coexist with arterial disturbances in KT-Weber, which is thought to

be caused by a somatic mutation in utero. Clinically, and for guidance in therapy, the structural and functional aspects of these complex disturbances can be unrav­eled in part using WB-LAS when combined with other imaging modalities, such as vascular scintigraphy (whole-body blood pool analysis), MRI, contrast venog­raphy and arteriography, and ultrasound techniques.

Lymphangio/adenoscintigraphy (by an analogous protocol applied to the peritu­moral site rather than the peripheral limb) is much more commonly performed today for sentinel lymph node delineation preparatory to determination of cancer staging. With improved sensitivity and reliability, radiolabeled immunoconju­gates or monoclonal antibodies could be directed against tumor-associated antigens and identification of tumor deposits accomplished by immunoscintigra­phy. Immunoscintigraphy may also permit tumoricidal drugs to be selectively targeted.

In summary, LAS is non-invasive, repeatable, easy to perform, and harmless to the lymphatic endothelial lining. Clear images of truncal lymph transport and draining nodes are routinely obtained. Follow-up studies can be used to document functional changes in lymphatic dynamics.

Another CDU application relates to vascular malformations involving the lym­phatic system. In fact, most “apparently” pure venous angiodysplasias exhibit a relevant lymphatic dysplastic component, and the opposite is also true. Safe and accurate use of CDU in vascular malformations has been proposed by most experts as first-line diagnostic technology, and detection of lymphatic abnormalities may be of help to focus on a proper treatment for these complex diseases.

The use of CDU investigation was proposed several years ago in specific LYM cases related to filariasis, and a few specific diagnostic markers (such as “the worm dance sign”) have been reported.

saphenous vein axis for the leg region (where they predominantly lie in normal

be atretic, hypo-functioning or totally absent; similarly, in cases of acute