Lymphatic anatomy & edema pathophysiology

What is the lymphatic system?

What structures does it consist of?

1-way drainage system composed of tiny vessels which carry fluid from the interstitial tissues to the blood system

• lymph vessels

• lymph nodes

• spleen, thymus, tonsils

What substances are in lymphatic loads?

• protein

• water

• WBC

• fat

• salts

• foreign debris

• microorganisms

What are the functions of the lymphatic system?

• immune surveillance: produces & distributes lymphocytes

• transport system: returns excess water, fats, protein, & large molecules to venous system

• prevent edemas

When do edemas form?

lymphatic load > lymphatic transport capacity

What are the consequences of edema?

• impaired cellular nutrition (d/t increased interstitial diffusion distance for O2 & nutrients)

• impaired tissue viability

• increased risk for infection & wounds

• pain

• impaired mobility & function

What are the levels of organization of the lymphatic system?

lymphatic capillaries —> pre-collectors —> collectors —> nodes —> trunks —> ducts

What is the function of the initial lymphatics/capillaries?

What is the structure of the initial lymphatics/capillaries?

absorb interstitial fluid from the interstitium

• single layer of epithelial cells

• no valves in the lumen

What is the function of the pre-collectors?

What is the structure of the pre-collectors?

connect the lymphatic capillaries to the lymphatic collectors; minimal absorption of fluid

• valves prevent backflow

• smooth mms for transport

What is the function of the lymph collectors?

What is the structure of the lymph collectors?

transport lymph to the lymph nodes & trunks

• valves prevent backflow

• smooth mms for transport, similar to veins

• lymphangion

What is a lymphangion?

How does it function?

region b/w the valves; the functional unit of the lymph collectors (smooth mm rings)

• influx of lymph —> stretch lymphangion —> smooth mms contract —> move fluid proximally

What is the lymphangiomotoricity?

frequency of lymphangion contraction

• 6-10x/min

• increases by 10x w/ increased lymphatic load

What 4 things improve the transport abilities of lymph collectors?

• respirations/diaphragmatic breathing

• arterial/venous pulsations

• skeletal mm movement

• newly formed lymphatic fluid

What are the functions of lymph nodes?

immune reactions

• allow macrophages to kill noxious substances (bacteria, viruses, toxins, dead cells)

• produce lymphocytes —> systemic immunity

• plays a role in spreading cancer

What will happen as a result of malignant tumors invading regional lymph nodes?

metastasis to other regions of the body

What will happen as a result of removal or irradiation of regional lymph nodes?

lymphedema

What regions drain into the axillary lymph nodes?

• UE

• skin of thorax above waist

• most of mammary gland

What regions drain into the inguinal lymph nodes?

• LE

• abs

• lumbar

• gluteal

• exterior genitalia

What are some of the lymphatic regions/territories?

• L head/neck drains to L Cx region

• R head/neck drains to R Cx region

• L upper trunk drains to L axilla

• R upper trunk drains to R axilla

• L lower trunk drains to L inguinal

• R lower trunk drains to R inguinal

Where do lymph fluid empty?

into the venous system at the venous angle (internal jugular & subclavian veins)

What are lymphatic trunks?

What happens at the lymphatic trunks?

largest lymphatic vessels that form the main parts of the transporting vessels

• lymphatic fluid is mixed into the venous blood via lymphovenous anastomoses

Which ANS innervates lymphatic trunks?

sympathetic

Which areas drain into the R lymphatic duct?

Which veins does the fluid enter?

• R head/neck, trunk, arm

• R internal jugular & subclavian veins (R venous angle)

Which areas drain into the L lymphatic duct?

Which veins does the fluid enter?

• lower body, L head/neck, trunk, arm

• L internal jugular & subclavian veins (L venous angle)

What are lympho-lymphatic anastomoses?

shared connections allowing drainage b/w 2 adjacent territories

• inter-axillary/axillo-axillary

• axillo-inguinal/inguino-axillary

• inter-inguinal/inguino-inguinal

What are lymphatic watersheds?

theoretical boudnary b/w lymphatic territories d/t scarcity of lymphatic vessels; areas that are crossed by the lymphatic capillaries but not the deep collectors

• median sagittal

• transverse

• clavicular

• spine of scapula

• chaps (gluteal)

What action promotes lymph flow through the thoracic duct?

deep breathing

What action promotes lymph flow through the lymphatic capillaries?

mm contraction

What is the MLD (manual lymphatic drainage) technique?

Usage of “pressure on” & “pressure off” stage to facilitate fluid entering the initial lymphatics and using the anastomoses to move fluid from congested areas to uninvolved areas

What is osmotic pressure?

What are the 2 osmotic pressure forces for normal circulation?

energy by which the more concentrated solution attracts water; low water concentration —> high osmotic pressure

• plasma colloidal osmotic pressure (COPp)

• interstitial colloidal osmotic pressure (COPi)

What is hydrostatic pressure?

What are the 2 hydrostatic pressure forces for normal circulation?

pressure exerted by fluid

• blood capillary pressure (BCP)

• interstitial pressure (IP)

What are colloids?

protein molecules

What is Starling’s Law?

rate & direction of fluid exchange b/w capillaries & interstitium determined by hydrostatic vs. osmotic pressures

• balance b/w filtration & absorption

What is filtration?

fluid leaves the vessel d/t high hydrostatic pressure pushing water across membrane

• typically at the arterial end

What is absorption?

fluid re-enters the vessel d/t osmosis

• typically at the venous end

What are the 4 forces for a normal circulation?

• blood capillary pressure (BCP)

• interstitial pressure (IP)

• plasma colloidal osmotic pressure (COPp)

• interstitial colloidal osmotic pressure (COPi)

What is blood capillary pressure (BCP)?

fluid pressure in the capillary at both arterial & venous ends

• major determinant of fluid movement in normal circulation

• determined by arterial pressure, venous pressure, pre- & post-capillary resistance

• favors filtration in the arteriole capillary

• favors absorption in the venous capillary

What happens w/ an increase in venous capillary BCP w/ venous insufficiency?

decreased absorption —> edema

What is interstitial pressure (IP)?

fluid pressure in the interstitium

• minimal effect on filtration or absorption

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What is plasma colloidal osmotic pressure (COPp)?

osmotic pressure d/t plasma protein concentration

• favors absorption in the venous end

What is interstitial colloidal osmotic pressure (COPi)?

What happens to COPi w/ lymphedema?

osmotic pressure d/t interstitial fluid protein concentration

• increases d/t reduced uptake of proteins of lymphatic system —> proteins stay in interstitium —> reduced absorption

Normal circulation results in..?

net filtration

• 90% of fluid & cells are absorbed by venous system

• 10% absorbed by lymphatics (ultrafiltrate)

What is ultrafiltrate?

What substances are included in ultrafiltrate?

lymph obligatory load

• large proteins & fats that cannot be reabsorbed through the venous system

What factors influence the lymphatic system?

• lymphatic load (LL)

• transport capacity (TC)

• functional reserve (FR)

What is lymphatic load (LL)?

amt. of substances that have to be removed from the interstitium by the lymphatic system (water, proteins, fat, cells)

What is transport capacity (TC)?

max amt. of lymph volume that can be transported by the lymphatics at a time

What is functional reserve (FR)?

TC - LL

What is lymphatic sufficiency in terms of TC & LL?

TC > LL

What is dynamic insufficiency in terms of TC & LL??

What does it lead to?

TC < LL d/t increased LL —> low protein edema (still healthy lymphatic system)

What is mechanical insufficiency in terms of TC & LL?

What does it lead to?

TC < LL d/t decreased TC —> high protein edema (diseased lymphatic system; lymphedema)

What are the normal lymphatic compensations?

• increased TC

• collateral circulation

• lympho-lymphatic anastomoses

• lympho-venous anastomoses

• plasma protein reduction by macrophages (???)

How does long-standing edema change and how?

pitting to fibrosis d/t accumulation of unabsorbed proteins in interstitial space

What is edema?

excess fluid in the interstitial space d/t increased filtration &/or reduced absorption

• can be localized or generalized

What conditions can cause generalized edema?

• CHF

• renal failure

• cirrhosis of liver (salt & water retention)

• nephrotic syndrome (low COPp)

How does CHF cause generalized edema?

inefficient heart pump —> increase hydrostatic pressure of venule end of capillaries —> reduced absorption

• L ventricular failure —> pulmonary capillaries involved 1st

• R ventricular failure —> systemic capillaries involved 1st

What does renal failure cause generalized edema?

reduced ability of kidneys to filter fluid —> more fluid reaches venous system

• COPp reduced —> reduced absorption

How does venous stasis cause localized edema?

How can you treat this?

increased hydrostatic pressure at venous capillary; can lead to lymphedema if long-standing

• treat w/ compression

How does inflammation cause localized edema?

How can you treat this?

vasodilation of capillaries —> increased blood flow

• increased membrane permeability to fluid & proteins

• treat w/ MLD & compression

How does lymphedema cause localized edema?

What can happen as a result of lymphedema?

How can you treat this?

lymphatic system unable to absorb lymph obligatory load d/t protein accumulation in the interstitium —> increased COPi

• causes chronic inflammation & reactive fibrosis of the affected tissues

• treat w/ Complete Decongestive Therapy

What is primary lymphedema?

lymphedema caused by congenital malformation of lymphatic system

What is secondary lymphedema?

lymphedema caused by known pathological condition:

• dissection or radiation of lymph nodes

• trauma

• chronic inflammation of lymph vessels/nodes

• cancer

• filariasis

• infection

• chronic venous insufficiency

How can you treat filariasis?

• hygiene

• exercise, compression, elevation

What are the characteristics of lymphedema?

• gradual onset

• pitting early

• distal to proximal

• squaring of toes, (+) Stemmer’s sign

• dorsum of foot “Buffalo hump”

• loss of ankle contour

• asymmetric if BIL

• cellulitis common

• rarely painful

• heaviness, achiness

• hyperkeratosis, papillomas, Peau d’Orange

• ulcerations unusual

What are the stages of lymphedema?

• stage 0: swelling not visible, but lymphatic transport impaired; Sx’s & subtle tissue changes may be noted

• stage 1: early onset of visible swelling, subsides w/ elevation, pitting

• stage 2: consistent volume change, elevation rarely reduces swelling, pitting

• stage 3: skin thickening, hyerpigmentation, papillomas, increased skin folds, fibrosis, no pitting, maybe fungal infections

What is lipedema?

What are the characteristics of lipedema?

BIL accumulation of fat deposition in the LE & buttocks

• gradual swelling of LE, sparing of the feet

• nonpitting

• varicose veins

• painful

How can you treat lipedema?

• weight control

• CDT

• liposuction

What are some functional outcome measures when examining pts w/ edema?

• Functional Assessment of Cancer Therapy - Breast (FACT-B +4)

• Disability of Arm, Shoulder, & Hand Questionnaire (DASH)