Chapter 41

### INTRODUCTION

The lymphatic system works to transport proteinaceous fluid from the tissues to the venous system. Lymphatic flow is aided by compression from the surrounding musculature and one-way valves within the lymphatic channels. The lymph system parallels the venous system and has many branches, from small lymphatic capillaries to larger lymphatic collecting ducts that drain into the lymph nodes.1 This system is also important for immune recognition of microbes and microbial products as part of the host response to infection. Inflammation of the lymphatics, or lymphangitis, can result from a variety of conditions, including allergies, insect stings, cancer, and infections.

Infections of the lymphatic system can be broadly grouped into two categories: infections of the lymph nodes or lymphadenitis, and infections of the lymph vessels or lymphangitis. If there is damage to the lymph vessel or surrounding tissues or interruption of the lymphatic flow from intraluminal obstruction, external compression, or surgical removal of lymphatic vessels, lymphedema may occur. As with any static fluid collection, lymphedema is a predisposing factor for subsequent infection.2,3

Lymphadenitis may occur with or without lymphangitis as a result of hematogenous spread, direct cutaneous inoculation, or extension from a nearby site of infection. A variety of pathogens (bacterial, fungal, mycobacterial, parasitic, and viral) may be the cause lymphadenitis, depending on the site of infection and how the area is drained lymphatically. Because the topic of lymphadenitis is extremely broad, it will not be the focus of this chapter; instead, the concentration will be on lymphangitis.

Lymphangitis most commonly occurs on the upper or lower extremities secondary to direct inoculation but can occur in any part of the body. Normal host tissue via direct inoculation (trauma, insect bite) can be affected, but there is a higher propensity for it to occur in tissue that has suffered lymphatic damage by trauma or as a postsurgical complication, with resulting chronic lymphedema.

A variety of pathogens cause lymphocutaneous syndrome, also known as sporotrichoid lymphangitis or nodular lymphangitis. A pathogen is introduced by cutaneous inoculation or trauma and proceeds to cause infection by spreading up lymphatic channels, often creating nodules along lymphatic vessels with overlying inflammatory changes.4,5 These pathogens can be grouped according to the timing of incubation into acute and chronic lymphangitis. Acute lymphangitis is mainly caused by bacterial pathogens, most often pyogenic organisms such as Staphylococcus and Streptococcus spp., although any bacterial pathogen infecting the subcutaneous tissues can be implicated in this syndrome. Chronic lymphangitis may be caused by organisms such as Sporothrix schenckii, Nocardia spp., mycobacterial species, endemic fungi, and Leishmania spp. Lymphatic filariasis has both acute and chronic components and is discussed in the section on acute lymphangitis.

### ACUTE LYMPHANGITIS

#### Pyogenic Organisms

The most common causes of acute lymphangitis are pyogenic organisms, most commonly Staphylococcus and Streptococcus spp., in conjunction ...

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