Lymphedema, Sentinel Node Detection and Lymphoscintigraphy

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Lymphedema is the accumulation of protein rich fluid in the interstitium, which causes chronic inflammation and reactive fibrosis of the affected tissues. It may result from:

Mechanical insufficiency due to injury to the lymph vessels or impairment of lymph flow due to paralysis, blockage or inadequacy of lymphatics
Dynamic insufficiency in which the lymph flow exceeds the transport capacity of the intact lymphatic system
Combined insufficiency

Anatomy of the Lymphatics

Capillaries: most distal, blind pouches which absorb interstitial fluid.
Precollectors: move lymph fluid from the capillaries to the collectors.
Collectors: are a series of valved chambers which propel lymph fluid towards the trunk through contraction of the muscle in the vessel walls.These are called lymphangions.
Lymph Nodes: the lymph fluid passes through the nodes, found in the articulations of the large joints , the mesentery and the neck (600-700). The lymph nodes filter waste and regulate protein content in the lymph fluid.

Types of Lymphedema

Lymphedema may be primary or secondary.

Primary lymphedema is a developmental abnormality and may be congenital, praecox or tarda.

Congenital is evident at birth, is bilateral and improves with age.
Praecox is evident after birth but remains before the age of 35 years and is unilateral.
Tarda becomes evident after 35 years, is rare and has hyperplastic pattern

Primary lymphedema accounts for 10% of all lymphedema. Underlying pathology may include:

Hypoplasia of lymph collectors (most common)
Hyperplasia of lymph collectors
Aplasia of single lymph collectors
Lymph node hypoplasia combined with fibrosis

Secondary Lymphedema is an acquired lymphedema accounting for about 90% of lymphedema. It may be caused by surgery, trauma,infection, malignant disease or filarial disease.

Signs and Symptoms

Swelling
Discomfort or pain
Tingling or numbness
Pressure or tightness
Heaviness in the limb
Increased infections
Fibrotic skin changes
Lymphorrhea
Decreased mobility
Impaired wound healing

Other Look Alikes

Post-phlebitic syndrome
Anasarca
Myxedema
Inflammatory arthritis
Complex regional pain syndrome
Idiopathic cyclic edema
Artificial lymphedema

Patient Evaluation

Patient evaluation includes detailed history taking, measurement tools and physical examination. Physical examination and history are the most important in diagnosis. If diagnosis uncertain then we may consider:

Lymphoscintigraphy
Indirect lymphography: a radiographic evaluation of the superficial lymphatics

Lymphoscintigraphy

Micropore filtered Tc-SC is injected intradermally in the web interspaces of the extremities to be evaluated. Tc-sulfur colloid requires an acidic pH to remain stable and this can cause the patient to experience burning. The area of injection is massaged for 2 minutes immediately after injection. A resolution collimator is used and images are acquired sequentially over the extremities.
A transmission scan should also be recorded to permit anatomic localization of the visualized areas

Sentinel Node Detection

Filtered Tc-sulfur colloid (1 mCi) is injected intradermally in 4 to 6 equal doses of 0.1 to 0.2 mL around the lesion or surgical site (about 0.5 to 1 cm from the lesion). Only about 5-8% of the injected dose will migrate. Imaging is started immediately after injection using a large field of view detector with a parallel hole collimator. Dynamic images are obtained at 20-30 seconds per frame for 30 to 45 minutes. Lateral or oblique static images are also acquired. Delayed static images are acquired at 1, 2, and 4 hours.