KEY NOTES CHAPTER 6: LOWER LIMB - Lymphoedema. Flashcards
What is the purpose of the lymphatic system?
- 80% of proteinaceous fluid in interstitium is reabsorbed by capillaries.
- lymphatic system also returns interstitial fluid into the venous circulation.
What is lymphoedema?
- Lymphoedema is accumulation of protein-rich interstitial fluid within skin and subcutaneous tissues.
- Over time, inflammation, adipose tissue hypertrophy and fibrosis may occur.
- This can be disfiguring and limits function.
How does the lymphatic system develop? (Embryology)
- mesoderm: lymphatic vessels, lymph nodes and spleen
- lymph sacs bud from venous endothelial cells and coalesce into primitive lymphatic capillaries (2nd month)
- valves are seen (5th month)
What is the anatomy of the lymphatic system?
The lymphatic system is divided into three parts:
1 Superficial system
- Suprafascial, within subcutaneous fatty tissue.
- Drains skin and subcutaneous tissue.
2 Deep system
- Subfascial, accompanies blood vessels.
- Drains muscle, tendon sheaths, nerves, periosteum and joints.
3 Visceral system
- Drains intestines, spleen, liver, thymus and lungs.
Deep and superficial systems are connected: ∘ Perforating lymphatic vessels ∘ Cubital fossa ∘ Popliteal fossa ∘ Inguinal region.
• Lymphoedema is limited to tissue superficial to deep fascia. Does not occur in muscle due to skeletal muscular pump.
Describe the flow of lymph in the body.
lymph capillaries -> lymph precollectors -> lymph collectors -> lymph nodes and lymphatic trunks -> lymphatic ducts
GI trunk R&L lumbar trunks(from lower limbs, lower trunk and external genitalia) + GI trunk -> cisterna chyli -> thoracic duct -> left internal jugular and subclavian veins.
Right jugular, supraclavicular, subclavian & parasternal trunks -> right lymphatic duct -> right internal jugular and subclavian veins.
What is the function of lymph nodes?
• Kidney-shaped aggregates of lymphoid tissue.
• Contain macrophages, plasma cells and lymphocytes that filter waste products:
∘ High molecular weight proteins
∘ Fats
∘ Cellular debris
∘ Foreign organisms, such as viruses and bacteria.
• Blood capillaries within lymph nodes absorb much of the water in lymph.
• Lymph nodes also produce lymphocytes.
What is the function of the lymphatic system?
1 Transport lymph from interstitial spaces to large neck veins.
2 Maintain fluid homeostasis.
3 Regulation of immunity.
How does lymphoedema occur?
• Due to insufficiency of lymphatic system.
• Untreated -> stagnation of water, protein and waste products in interstitium.
• Tissue damage, increased diffusion distances and impaired circulation of macrophages and
lymphocytes -> infection.
• Repeated cellulitis and lymphangitis -> damage to lymphatics.
2 mechanisms:
1 High volume insufficiency.
2 Low volume insufficiency.
What is simple oedema and what are the causes?
• Accumulation of low-protein fluid in the interstitium -> swelling and pitting oedema.
Causes ∘ Cardiac insufficiency ∘ Immobility ∘ Chronic venous insufficiency ∘ Hypoproteinaemia ∘ Pregnancy ∘ Medication, e.g. calcium channel blockers or NSAIDs.
How does high volume insufficiency occur?
Lymphatic load exceeds transport capacity of an intact lymphatic system.
Persistent oedema (months) -> increased intra-lymphatic pressure -> damage to vessel walls and valves -> fibrosis and protein leak.
High protein concentration -> increases interstitial oncotic pressure -> accumulation of water -> high-protein oedema = lymphoedema.
How does low volume insufficiency occur?
- Reduced transport capacity cannot deal with normal quantities of lymph.
- Common causes: surgery, radiation, filariasis.
How is lymphoedema classified?
Primary (by age of onset) or Secondary (cause).
.
• Developmental abnormality.
∘ Lymph vessel abnormalities are most common.
∘ More rarely, fibrosis or agenesis of lymph nodes.
• Abnormalities are believed to be present at birth, but may not manifest as lymphoedema
until later in life.
.
Lymphoedema congenita
• VEGFR3 gene mutation.
• Lymphoedema present at birth or within 2 years.
• 10% of primary lymphoedema.
• F:M 3:1
• 60% in the lower limb.
• Lymphangiography: severe hypoplasia or aplasia.
• Familial lymphoedema congenita ‘Nonne-Milroy syndrome’.
Lymphoedema praecox
• 80% of primary lymphoedema.
• Presents at age 2 - 35 years, typically at puberty.
• F:M 10:1 (?Oestrogen related)
• Most are unilateral; left leg affected more frequently than the right.
• Lymphangiography: hypoplasia.
• Familial lymphoedema praecox ‘Meige disease’.
Lymphoedema tarda
• Presents after 35 years.
• ~ 10% of cases.
• Lymphangiography: hyperplasia.
What are the causes of secondary lymphodema? (Five ‘I’s)
1 Invasion by tumour
- Primary lymphatic tumours
- Secondary tumours.
2 Infection
- Most common worldwide: filariasis (Wuchereria bancrofti parasite, transmitted by mosquitos).
- Massive swelling of legs and genitalia = elephantiasis.
- Lymphogranuloma, TB, recurrent infections.
3 Inflammation
- Snake or insect bites
- Burns.
4 Irradiation
5 Iatrogenic causes
- Lymph node dissection
- Varicose vein stripping, chronic venous insufficiency.
How is lymphedema staged?
International Society of Lymphology:
Stage 0 (subclinical stage).
• Swelling not evident despite impaired lymph transport.
Stage I (reversible stage). • Pitting oedema subsides with limb elevation. • No secondary soft tissue changes.
Stage II (spontaneously irreversible stage).
• Lymphostatic fibrosis, hardening of tissues, eventual loss of pitting oedema.
• Swelling does not reduce significantly with elevation.
• Frequent soft tissue infections.
• Stemmer’s sign is positive:
dorsal fold of skin cannot be pinched and lifted at base of second toe or middle
finger.
∘ Negative Stemmer’s sign does not exclude lymphoedema.
Stage III (lymphostatic elephantiasis).
• Extreme increase in volume.
• Skin thickening, hyperpigmentation, deep skin folds, fat deposits, papillomas.
• Within each stage, swelling can be assessed by volume as:
∘ Mild: <20% excess limb volume
∘ Moderate: 20-40% excess limb volume
∘ Severe: >40% excess limb volume.
What are the differential diagnoses?
∘ Lipodystrophy (lipoedema)
- Classically stops at the ankles; does not involve feet.
∘ Deep venous thrombosis
∘ Ruptured Baker’s cyst.
∘ Myxoedema
∘ Oedema due to:
- Cardiac, pulmonary, hepatic or renal causes
- Gastrointestinal, gynaecological or urological causes
- Infectious diseases.
• Simple oedema:
∘ pitting oedema, improves within hours of elevation.
• Established lymphoedema:
∘ non-pitting oedema, improves within days of elevation.
∘ skin is thick and hyperkeratotic.
∘ Secondary lymphoedema has a definable cause.
How is limb swelling measured?
- Serial photography
- Standardised circumferential limb measurement.
- Limb volume: water displacement
- 3D cameras, perometry (using lasers or light).
What is malignant transformation of lymphoedema called?
• Malignant transformation (lymphangiosarcoma) occurs in 10% of severely affected
patients after 10 years.
∘ 5 year survival <10%.
• Stewart-Treves syndrome: angiosarcoma arising within chronically lymphoedematous
upper limb, following mastectomy and axillary lymph node dissection for breast cancer.
How are patients investigated?
Direct lymphangiography Indirect lymphangiography Lymphoscintigraphy Indocyanine green (ICG) lymphography Magnetic resonance lymphography
How is direct and indirect lymphangiography performed?
Direct
• Patent blue dye is injected into the dorsal foot or hand to identify lymphatics.
• Lymph trunks are then cannulated and injected with oily radio-opaque contrast.
• Lymph channels are then imaged radiologically.
• Seldom used - may worsen lymphoedema by damaging valves, causing fibrosis.
Indirect
• Water-soluble contrast material is injected intracutaneously.
• Contrast is preferentially absorbed by the fine lymphatic capillaries.
• The lymphatic system is then demonstrated radiologically.
• Regional lymph nodes cannot be identified by this method.
How is lymphoscintigraphy performed?
• This has largely replaced direct lymphangiography.
• Radioactive tracer is injected intradermally and taken up by lymphatics.
∘ Can also be injected subfascially to visualise the deep system.
• A gamma camera visualises radiation emitted by the tracer, providing a map.
∘ Also shows rate of lymph uptake and movement through lymph vessels.
• Technetium-99m is often used to label tracers, e.g. dextran, sulphur colloid, albumin.
What is indocyanine green (ICG) lymphography?
• Relatively new imaging method.
• Fluorescent dye that binds to plasma proteins.
• Injected intradermally; taken up by lymphatic capillaries.
• By illuminating skin surface with near-infrared light source, dynamic images of superficial lymphatic flow are obtainable within minutes.
• ICG emission is detectable by special cameras e.g. Photodynamic Eye (PDE) or
SPY® System.
• Can be used intraoperatively to map lymphatics and verify results of surgery.
How does magnetic resonance lymphography work?
MRI with powerful 3T magnets produce detailed images without contrast injection.
