Lymphangitis (Infected Lymphatic Vessels)

The lymphatic system works to drain out excess tissue fluid, filter out debris, neutralize any pathogens and return the fluid to the bloodstream. In this way the lymphatic system is closely related to both the immune system and vascular system. The main structures in the lymphatic system are the lymph channels and lymph nodes which are distributed throughout the body. The spleen which is located under the left ribcage is also part of the lymphatic system as it functions as one very large lymph node. Lymphatic channels include the passageways through which lymph flows and the walled vessels. It directs the lymphatic fluid to the lymph nodes and carries it to the blood stream. However, it is prone to the same injury as any other part of the body.

What is lymphangitis?

Lymphangitis is the term for inflammation of the lymphatic channels. Since the vessels are hollow walled structures, it is these walls that become inflamed in lymphangitis. It mainly occurs with an infection. Most of the time the infection does not originate in the lymphatic vessel (primary) but instead spreads from a neighboring sites or distant site to involve the vessel (secondary). Lymphangitis can progress into a systemic infection and even lead to death if left untreated.

Pathophysiology

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Entry into a lymphatic vessel may be direct through an injury on the skin which allows microorganisms to enter the vessel. It usually involves the surrounding skin and connective tissue (cellulitis). At other times it extends from another site of infection and the skin and surrounding tissue may not be directly involved. However, the infection can then extend from the lymphatic vessels into the surrounding tissues (perilymphatic tissues) thereby producing cellulitis or abscess formation.

Once in the lymphatic vessel it causes inflammation of the vessel wall and inflammatory exudate fills the vessel at the site. The infection then extends along the vessel in the direction of the lymph flow (proximally). It enters the lymph node through the afferent vessel and is usually blocked here. The lymph node isolates the infection but is also inflamed in the process. Should the lymph node not be able to contain the infection, the microorganisms pass out of the efferent lymph vessels and can then enter the venous circulation (bloodstream). This may lead to bacteremia or sepsis and quickly progress to more severe complications including death.

Causes of Lymphangitis

Almost all cases of lymphangitis are due to a bacterial infection. In a person with normal immune defenses the spread of the infection is not rapid. The lymph nodes are often able to contain the infection. It may resolve here or provide sufficient time for medical intervention before it progresses to bacteremia or sepsis.

Of the various species, group A beta-hemolytic streptococci (GABHS) are the most common cause. Primary infection of the lymphatic vessels are almost never seen and GABHS lymphangitis is more commonly a complication of cellulitis. Other common yet less frequently seen bacteria involved in lymphangitis includes Staphylococcus aureus or Pseudomonas species.

Uncommon bacterial causes may include Streptococcus pneumoniae, Pasturella multocida (dog or cat bites) and Aeromonas hydrophila (swimming in contaminated water). Non-bacterial causes are mainly due to parasites like Wuchereria bancrofti which is spread by mosquitoes and cause lymphatic filariasis.

Individuals who are immunocompromised are at risk of developing lymphangitis caused by any number of microorgansisms including bacteria that rarely seen in persons with a healthy immune system, parasites and fungi.This may include a person living with HIV, uncontrolled diabetes mellitus, patients on immunosuppressants and other systemic illnesses.

Signs and Symptoms

The characteristic feature is the presence of red painful streaks visible on the skin surface. This correlates to the course of the inflamed lymphatic vessel. Regional lymph node(s) are enlarged and painful(lymphadenitis). When the infection extends into the surrounding tissue (cellulitis), there is swelling, pain and redness of the entire area (cellulitis) and there may be a painful lump (abscess). The affected area is usually warmer than surrounding unaffected tissue. There may also be visible blistering of the skin.

Other signs and symptoms may include :

• Fever and chills
• Lymphadenopathy (swollen lymph nodes) of the surrounding unaffected nodes, particularly in the elbow, armpit, groin or even neck.
• Headaches
• Loss of appetite
• Muscle aches and general body pains
• Malaise

A high fever with elevated blood pressure (hypertension), raised heart rate (tachycardia), change in consciousness, convulsions, severe dizziness, intense nausea and vomiting are serious clinical features of a rapidly progressing infection. This can fairly quickly lead to death if left untreated.

Diagnosis of Lymphangitis

A complete blood count will indicate infection with features such as a raised white blood cell count. A blood culture may also be necessary particularly in bacteremia. Aspiration of pus should be done carefully to prevent dissemination. Cytology and culture on the aspirated fluid may then be conducted.

Treatment of Lymphangitis

The treatment depends on the causative organisms. An abscess should be drained. Oral antibiotics and other antimicrobial agents are only useful if the infection has not reached the bloodstream or spread extensively into surrounding tissue.Intravenous administration of antibiotics may otherwise be indicated particularly when there is evidence of a systemic infection.

In terms of the antibiotics used, a cephalosporin a synthetic penicillin may be administered. If MRSA (methicillin-resistant Staphylococcus aureus) is suspected to be the cause then clindamycin or trimethoprim-sulfamethoxazole may be used. Topical antimicrobial applications like mupirocin may also be indicated for cellulitis and at the site of a wound.

Analgesics may be used for pain relief and anti-inflammatory drugs to reduce inflammation and swelling. Warm compresses may also be useful to reduce pain and inflammation.