Secondary Lymphoedema

This is the most common form of lymphoedema. There are several well recognised causes.

Filariasis

This is the commonest cause of lymphoedema worldwide, affecting up to 100 million individuals. It is particularly prevalent in Africa, India and South America where 5—10 per cent of the population may be affected. The viviparous nematode Wucheria bancrofti, whose only host is humans, is responsible for 90 per cent of cases and is spread by the mosquito. The disease is associated with poor sanitation. The parasite enters lymphatics from the blood and lodges in lymph nodes where it causes fibrosis and obstruction, due partly to direct physical damage and partly to the immune response of the host. Proximal lymphatics become grossly dilated with adult parasites. The degree of oedema is often massive, in which case it is termed ‘elephantiasis’. Immature parasites (microfilariae) enter the blood at night and can be identified on a blood smear, a centrifuged specimen of urine or in lymph itself. A complement fixation test is also available and is positive in present or past infection. Eosinophilia is usually present. Diethylcarbamazine destroys the parasites but does not reverse the lymphatic changes; although there may be some regression over time. Once the infection has been cleared treatment is as for  primary lymphoedema. Public health measures to reduce mosquito breeding, protective clothing and mosquito netting  may be usefully employed to combat the condition.

Malignancy and its treatment

This is the most common cause of lymphoedema in developed countries. Hodgkin’s and non-Hodgkin’s lymphoma may present with lymphoedema, as may malignant melanoma which has metastasised to regional lymph nodes and malignancy of the pelvic organs (ovary, uterus, bladder), anus, prostate, testes, penis and breast (peau d’orange). More often lymphoedema is a result of treatment, either surgical excision of draining lymph nodes and/or radiotherapy. Lymphoedema following treatment for breast carcinoma is the commonest example, but fortunately this is decreasing in incidence as surgery for the condition has become more conservative. Lymphoedema may occur after radical mastectomy (up to 60 per cent), modified radical mastectomy (up to 20 per cent), local excision with either axillary node clearance or radiotherapy (less than 5 per cent), and local excision with axillary node clearance andradiotherapy (up to 40 per cent).

Trauma

This is an unusual cause of lymphoedema but is especially seen after degloving injuries of the extremities.

Acute cellulitis

As described above, acute bacterial lymphangitis is a frequent­ly observed triggering event for secondary lymphoedema.

Other causes

Other rare, but well-documented, causes of secondary lym­phoedema include tuberculosis, rheumatoid arthritis (chronic inflammation and lymph node fibrosis), and snake and insect bites. It is likely that deep venous thrombosis, chronic venous insufficiency and superficial thrombophlebitis can lead to lymphoedema. Indeed, lymphatic abnormalities are frequently observed in patients who have the skin changes of chronic venous insufficiency and venous ulceration.

Factitious Lymphoedema

This may be caused by application of a tourniquet (a rut and sharp cut-off is seen on examination) or ‘hysterical’ misuse.

Investigation of Iymphoedema

Are investigations necessary? Many clinicians diagnose lymphoedema purely on the basis of history and examination, especially when the swelling is mild and there are no apparent complicating features. Severe swelling, with unusual features, or where there may be more than one pathology contributing to the clinical picture usually warrants further investigation. Not only will this allow the diagnosis to be confirmed, but it may also provide useful prognostic information and guide management decisions.

Investigation techniques

Listed are several procedures used in the investigation of Iymphoedema.

‘Routine’ tests. A full blood count, plasma urea and electrolytes, creatinine, liver function tests, chest radiograph and midnight blood

Contrast lymphangiography. Although few centres now perform this technique, it remains the standard by which all other lymphatic imaging is judged and provides precise information about the anatomy of the lymphatic system. It is now generally reserved for preoperative evaluation of patients with megalymphatics who arc being considered for bypass or fistula ligation.

Technique (Kinmonth, Browse, Wolfe). The patient is admitted for limb elevation to reduce swelling and facilitate lymphatic cannulation. Originally a vital dye such as patent blue was injected and its ascent in the lymphatics to the regional nodes (in about 5—111 minutes) simply observed with the naked eye (visual lymphangiography). In patients with obliterated lymphatics dermal backtlow could he observed soon after injection and the appearance of dye at the groin was delayed. This technique was soon replaced with direct contrast lymphangiography. Under local anaesthesia, a small transverse incision is made in the dorsum of the foot after I ml of isosulphan blue has been injected subcutaneously to identify the lymphatics. Lymphatics are dissected out under loupe magnification and a 30G needle used to infuse lipid-soluble contrast at a rate of I ml in 8 minutes to a maximum of 7 ml (taking about 1 hour) into each limb. Serial radiographs are taken during injection and at intervals up to 24 hours. As the procedure is uncomfortable and patients are often unable to lie still, it is frequently performed under general anaesthesia. In a normal limb the injection will usually fill between five and is superficial valved medial lymphatic vessels in the thigh as well as most of the inguinal lymph nodes; iliac nodes fill at between 30 and 45 minutes. Deep lymphatics, which are frequently paired and follow the deep vessels, as well as the lateral superficial lymphatics are not usually seen except in disease. Four main anatomic patterns of lymphatic disease are identified by lymphangiography; namely congenital hyperplasia, distal obliteration (hypo/aplasia), proximal obliteration with distal hyperplasia and proximal obliteration with distal obliteration.

Isotope lymphoscintigraphy. This has largely replaced contrast lymphangiography and is used in most centres as the primary diagnostic technique.

Technique

The patient lies supine. Radioactive technetium-labelled antimony sulphide colloid particles (10 nm diameter) are injected into the web space between the second and third toes (or fingers) with a 27G needle bilaterally. This is associated with 5—10 seconds of stinging, about which the patient must be warned. The particles are specifically taken up by lymphatics and about 30 per cent of the tracer is absorbed in 3 hours. Immediately after injection a gamma camera is positioned to include the inguinal region in its upper field. During the first hour, 12 5-minute dynamic anterior exposures are taken. The patient is requested to exercise with a foot ergometer (to permit reproducible exercise and tracer clearance) for 5 minutes initially and then for 1 minute out of every subsequent 5 minutes. At 1 and 3 hours, and in selected patients at 6 and 24 hours, 20-minute whole body exposures are taken. Between exposures the patient is ambulant.

Interpretation.

In a normal leg activity ascends the anteromedial aspect of the limb. Several lymph channels are seen in the calf but in the thigh they cannot usually be distinguished. Normally, radioactivity first appears in the inguinal (axillary) nodes at between 15 and 60 minutes and is symmetrical; individual nodes cannot usually be distinguished. At 60 minutes there is only faint uptake in the liver and bladder. At 3 hours there is intense activity over the liver and good symmetrical uptake in inguinal, pelvic and abdominal lymph nodes; the thoracic duct may also be seen. Most groups interpret lymphoscintigraphy qualitatively as attempts to perform quantitative assessment have produced inconsistent results. It is not possible to distinguish primary from secondary lymphoedema with certainty. However, lymphoscintigraphic patterns can be correlated to some extent with Iymphangiographic findings.

• Distal obliteration is also known as aplasia or hypoplasia and is asso­ciated with little or no removal of tracer from the injection site, little or no activity in the regional nodes at I or 3 hours, and a cutaneous pattern of tracer distribution (dermal backflow). Although the time taken for radioactivity to reach the groin is prolonged, onward passage from there is usually normal.
• Proximal obliteration is associated with normal uptake from the injection site and appearance of tracer in inguinal nodes. However, there is a failure of tracer to progress from the inguinal lymph nodes and collaterals crossing over to other side are present.
• Lymphangectasia is associated with abnormal collections of tracer activity indicating extravasation into the peritoneal or pleural cavities or into viscera. Lymphocoeles and dilated lymph channels (mega­lymphatics) are also seen.

Computerised tomography. The main role of CT is to exclude pelvic or abdominal mass lesions. Although lymphoedema itself can be visualised on CT, it is of little diagnostic value in this respect.

Magnetic resonance Imaging. Magnetic resonance imaging can provide clear images of lymphatic channels and lymph nodes, and can also distinguish venous and lymphatic disease as the cause of a swollen limb. However, it cannot at present provide the information available from lymphoscintigraphy, and as a cross-sectional imaging technique it appears to have little advantage over CT.

Pathological examination. In cases where malignancy is suspected, samples of lymph nodes may be obtained by fine needle aspiration, needle core biopsy or surgical excision.