What causes edema during the inflammatory process?

Causes of Edema During the Inflammatory Process

Increased capillary permeability is the primary cause of edema during the inflammatory process.

Pathophysiology of Inflammatory Edema

• Inflammation leads to increased vascular permeability or capillary leak, allowing fluid to move from blood vessels into the interstitial space 1
• This increased permeability is mediated by chemical mediators including bradykinin, serotonin, and prostaglandins 1
• The inflammatory process causes dilatation of the myocardial vascular bed with hyperemia, which contributes to the edema formation 1
• Edema occurs when the balance between hydrostatic and oncotic pressure gradients is disrupted, particularly when capillary permeability increases 2

Mechanisms of Increased Capillary Permeability

• Inflammatory mediators cause endothelial cells to contract, creating gaps between them that allow fluid and proteins to leak into surrounding tissues 1
• The increased vascular permeability leads to a net expansion of the extracellular space 1
• This process allows plasma proteins to cross into the interstitial space, creating interstitial edema 2
• When fluid deposition exceeds the capacity of the lymphatic system to remove fluid, extravascular water accumulates 2

Role of Inflammatory Mediators

• Bradykinin is a key mediator that increases vascular permeability during inflammation 1
• Serotonin and prostaglandins also play important roles in mediating the increased permeability 1
• These mediators act on endothelial cells to increase the spaces between them, allowing fluid to leak out 1
• The proximate cause of all edema is attributed to increased vascular endothelial permeability 1

Comparison with Other Potential Causes

• While vasodilation of blood vessels (option A) does occur during inflammation and contributes to hyperemia, it is not the primary cause of edema 1
• Endothelial cell expansion (option C) is not a recognized mechanism for edema formation during inflammation 1
• Emigration of neutrophils (option D) occurs during inflammation but is not the primary cause of edema; in fact, specialized endothelial domes form to maintain barrier integrity during neutrophil emigration 3

Clinical Significance

• Edema is a normal response to injury but becomes problematic when it persists beyond the inflammatory phase 4
• Persistent edema can delay healing and contribute to complications such as pain and stiffness 4
• The magnitude and spatial extent of edema depend on the severity of the inflammation 1
• Early prevention and management of edema are critical to prevent progression to chronic complications 4