Orbital cellulitis pathophysiology

Orbital cellulitis Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Orbital cellulitis from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
X Ray
CT
MRI
Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Orbital cellulitis pathophysiology On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Orbital cellulitis pathophysiology All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Orbital cellulitis pathophysiology
CDC on Orbital cellulitis pathophysiology
Orbital cellulitis pathophysiology in the news
Blogs on Orbital cellulitis pathophysiology
Directions to Hospitals Treating Orbital cellulitis
Risk calculators and risk factors for Orbital cellulitis pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Tarek Nafee, M.D. [2]

Pathogenesis

Orbital cellulitis occurs secondary to microbial infiltration of the deep soft tissue cells surrounding the eye, behind the orbital septum. Damage to the cells triggers an acute inflammatory response resulting in vasodilation, increased vascular permeability, and induction of a cascade of inflammatory markers and white blood cell chemoattractants.

Extension of adjacent infection

Orbital cellulitis may spread from direct extension of an acute or chronic adjacent infection. This includes the following: -Rhinosinusitis (Ethmoid sinusitis and pansinusitis) -Dacryocystitis, Dacryoadenitis -Otitis media -Dental infections

Direct inoculation

Microbes inoculated in the retroseptal orbital space by traumatic or iatrogenic means.

Traumatic

Occur as a result of direct inoculation of the microbe due to trauma:
-Fracture
-Penetration by a foreign body

Iatrogenic

Occur as a result of direct inoculation during surgical procedures such as:
-Ocular or periocular surgeries
-Paranasal Sinus surgeries
-Other ENT surgeries

Microscopic Pathology

• Staphylococcus aureus, is a gram-positive bacterium which is the most common of staph infections. Staphylococcus aureus infection can spread to the orbit from the skin. Staph organisms are able to produce toxins which promote their virulence which leads to the inflammatory response seen in orbital cellulitis. Staphylococcus infections are identified by a cluster arrangement on gram stain. Staphylococcus aureus forms large yellow colonies (which is distinct from other Staph infections such as Staphylococcus epidermis which forms white colonies).

• Streptococcus pneumoniae, is also a gram-positive bacterium responsible for orbital cellulitis due to its ability to infect the sinuses (sinusitis). Strep organisms are able to determine their own virulence and can invade surrounding tissues causing an inflammatory response seen in orbital cellulitis (similar to Staphyloccoccus aureus). Streptococcal infections are identified on culture by their formation of pairs or chains. Streptococcus pneumoniae produce green (alpha) hemolysis, or partial reduction of red blood cell hemoglobin.