Here's how I understand this; please correct me if I'm wrong: Fibrin exudation is part of the acute inflammatory response if the inflammatory stimulus is a lacerating wound, (such as, in this patient, perforated diverticulitis), along with platelets and other clotting factors, in order to clot the wounded area. Hence in this patient who died 2 days following acute perforated diverticulitis, the inflammatory exudate surrounding the liver would most likely contain fibrin (not collagen, since the inflammation is acute and not chronic). Fibronectin and proteoglycans, the other two options, are extracellular matrix proteins.

Appears to be fibrin deposition secondary to bacterial peritonitis.

Fibrin deposition initiated by peritonitis is thought to be an important local defense mechanism because it sequesters and walls off bacterial spillage."

Rotstein 1986

• The introduction of pathogenic bacteria into the normally sterile environment of the peritoneum induces a robust inflammatory response, with the secretion of fibrin that subsequently traps and encases bacteria.

• While important in limiting the spread of infection, it can also predispose to the formation of abscesses.