Pathology of encapsulating peritoneal sclerosis.

Pathology findings of encapsulating peritoneal sclerosis (EPS) are reviewed to establish histologic criteria for a diagnosis of EPS. The typical macroscopic finding is a cocoon-like encapsulation of the entire intestine. This encapsulation is frequently accompanied by fibrin deposition, focal bleeding on the peritoneum, and various quantities of bloody ascites. A thin membrane on the visceral peritoneum contributes to the formation of the intestinal encapsulation. Histologically, the membrane is composed mainly of organized fibrin, probably derived from plasma exudation from the peritoneal microvasculature. Peritoneal fibroblasts appear swollen and exhibit an increased level of cellularity, accompanied by expression of various activation and proliferation markers. According to the "two-hit" theory of EPS pathogenesis, deterioration of the peritoneum as a result of the peritoneal dialysis (PD) procedure (the first "hit") and superimposition of inflammatory stimuli such as infectious peritonitis (the second "hit") are thought to play key roles in the pathogenesis of EPS. Based on histologic examination of peritoneal biopsy specimens, the detection of fibrin deposition and fibroblast phenotypic alteration were proposed as important findings for early diagnosis of EPS. Persistent inflammatory changes are also predictive of the future onset of EPS. Careful histologic evaluation of peritoneal biopsy specimens, combined with Laparoscopic observations after withdrawal of PD, is required for the early diagnosis and treatment of EPS.