Catarrhal Inflammation

Catarrhal inflammation is a type of exudative inflammation that affects mucous membranes exclusively. Its hallmark feature is a profuse fluid exudate — either serous (watery) or mucous in nature — accompanied by localized hyperemia at the inflammation site.

This is one of the most common — and typically mildest — forms of inflammatory response. Catarrhal inflammation is a typical reaction of mucous membranes in the respiratory tract, gastrointestinal tract, and other organs to irritation or infection.

Etiology and pathophysiology

Catarrhal inflammation may be triggered by various factors, including viruses (e.g., rhinoviruses), bacteria, allergens, or chemical and thermal irritants.

Pathophysiologically, injury induces vasodilation (hyperemia) and increased permeability of the mucosal vessels. Consequently, the fluid component of blood (serous exudate) emerges onto the mucosal surface. Simultaneously, the irritation stimulates goblet cells and mucous glands to produce excessive mucus (mucin), which mixes with the exudate.

Clinical Significance

The clinical manifestations of catarrhal inflammation are well known — it characterizes the early stages of many common colds.

• In the nasal cavity, it presents as rhinitis (runny nose) with copious watery or mucous discharge.
• In the trachea and bronchi, it manifests as tracheitis and bronchitis, accompanied by coughing and sputum production.
• In the stomach and intestines, it appears as acute gastritis and enteritis, marked by the secretion of large amounts of mucus.

Catarrhal inflammation generally has a favorable prognosis. It may resolve completely once the underlying cause is eliminated, without leaving any tissue damage. However, if a secondary bacterial infection occurs or immune function is compromised, it may progress to a more severe form, such as purulent inflammation.