**25. Pathophysiology**

Septic emboli are transported to the lung via the hematogenous route from various sources of infection. These emboli cause occlusion of the small, peripheral pulmonary arteries leading to pulmonary infarction which could further complicate to microabscesses. Extravasation from the bronchial arteries – "pulmonary hemorrhages", may cause peripheral consolidation. (Fig 3- Flow chart).

**Etiology SPE 2005** Catheter &device

related

IVDA

Lemierre's Syndrome

Extra-pulm focus

of infection

49%

78% IVDA

Septic emboli are transported to the lung via the hematogenous route from various sources of infection. These emboli cause occlusion of the small, peripheral pulmonary arteries leading to pulmonary infarction which could further complicate to microabscesses. Extravasation from the bronchial arteries – "pulmonary hemorrhages", may cause

**Etiology SPE; 1978**

20% others

29%

Fig. 2. (a & b): Causes of Septic Pulmonary Embolism

(Cook et al., 2005; MacMillan et al., 1978)

peripheral consolidation. (Fig 3- Flow chart).

**25. Pathophysiology** 

8%

14%

A peculiar subtype is Lemierre's syndrome (postanginal sepsis), a severe illness caused by the anaerobic bacterium, Fusobacterium necrophorum which typically occurs in healthy teenagers and young adults. The infection originates in the throat as tonsillo-pharyngitis, odontogenic infection, mastoiditis or sinusitis and spreads via a septic thrombophlebitis of the tonsillar vein and internal jugular vein. The ensuing bacteremia is complicated by septic emboli to a range of sites such as lung, joints, and bones. Pulmonary involvement in Lemierre's syndrome has been reported in up to 97% with SPE, lung abscesses and empyema (Golpe et al., 1999; Riordan & Wilson, 2004; Sinave et al., 1989). The causative organisms of Lemierre's syndrome include the anaerobic gram-negative Fusobacterium species, and also Eikenella, Porphyromonas, Streptococci and Bacteroides. Recently, methicillin-resistant Staphylococcus aureus has been identified as a new causative agent (Riordan & Wilson, 2004).

Fig. 3.
