Fibrinösen

Fibrinösen, or fibrinous, describes a type of exudate or tissue change characterized by the presence of fibrin, a polymer formed during the blood coagulation process. It results from increased vascular permeability during inflammation, allowing fibrinogen to escape into tissues or body cavities where thrombin converts it to fibrin. The fibrin forms a delicate, eosinophilic mesh that can coat serous membranes or surfaces and may appear pale or glassy under microscopic examination.

Histologically, fibrinösen exudates consist of a fibrin network mixed with inflammatory cells and protein-rich fluid. Over time the fibrin can organize and lead to adhesions between overlapping serosal surfaces. If the underlying cause persists, the process may become chronic, with ongoing inflammation and fibrous tissue formation.

Fibrinösen exudates are commonly encountered on serous membranes such as the pleura (fibrinous pleuritis), pericardium (fibrinous pericarditis), and peritoneum (fibrinous peritonitis). They can also occur in meninges, joints, and other mucosal surfaces. Clinically they are often associated with acute infections, autoimmune diseases, or traumatic injury. The presence of fibrinous exudate helps guide diagnosis toward inflammatory or infectious etiologies and may prompt anti-inflammatory treatment, management of the underlying cause, and, when necessary, procedures to address adhesions or effusions.