Septic embolus

Author: Amy Dendale, 5th year medical student, University of Auckland. Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, October 2015.

What is a septic embolus?

A septic embolus is a blood clot containing bacteria that become dislodged from their source and travelled through the body. Septic emboli become trapped in small terminal blood vessels, blocking them.

Septic emboli damage the body tissues in two ways:

  1. They completely or partially reduce the blood supply
  2. They introduce an infectious agent into a damaged site

Septic emboli are a consequence of an infection and their presence should always prompt a search for the primary source. Their consequences range from mild skin changes to serious life threatening infections.

Who gets septic emboli?

Septic embolic occur in people at increased risk of infections, particularly of the heart lining and blood vessels. These include:

What causes septic embolisation?

Septic emboli come from a site of infection, where bacteria are present in large numbers and various inflammatory processes and turbulent blood flow increase the likelihood of clot formation. An infected clot, or small fragment of clot, becomes dislodged and comes to rest at a distal location. Local tissue damage occurs due to the combined effects of ischaemia (lack of oxygen supply) and infection.

There are various sources of septic emboli.

What are the clinical features of septic emboli?

People with septic emboli tend to exhibit classic but non-specific signs of infection, including fever, fatigue, and an increased heart rate. There have been reports of asymptomatic primary infection and subsequent septic embolisation, particularly from the spleen.

The specific clinical findings of septic embolisation depend on where the clot gets lodged. This may include any part of the body, such as the lungs, causing lung infections and accesses, or the skin, causing distinctive painful lesions.

Skin manifestations include:

Emboli may affect internal organs:

How is the diagnosis of septic embolic made?

The diagnosis of septic embolisation is not always straightforward and involves a range of different disciplines.

Blood tests


Establishing the source of the septic emboli is the key to diagnosis. While some potentially causative infections may be diagnosed clinically, others require more extensive investigation.

What treatments offered for septic emboli?

The mainstay of treatment is to control the original source of infection. How this is best achieved depends on the source, and may include:

What is the longterm outcome of septic emboli?

Septic embolisation may be a mild or very severe condition, and the longterm outcome depends on which organs are involved, the severity of the precipitating infection, and the general health of the patient preceding the infection.

In healthy people, or those with only mild infection and cutaneous emboli, active treatment of the primary source of infection is often sufficient to clear disease and prevent further septic embolisation.

Where septic emboli have caused extensive infection of the limbs, gangrene may develop. This may necessitate amputation of affected areas.

Involvement of internal organs, particularly lungs and brain, may progress to overwhelming systemic infection (sepsis) and death. Involvement of internal organs does not preclude full recovery however the treatment course is often long and difficult.

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