Histologic criteria for diagnosing encapsulating peritoneal sclerosis in continuous ambulatory peritoneal dialysis patients.

To establish histologic criteria for a diagnosis of encapsulating peritoneal sclerosis (EPS), we investigated 69 peritoneal biopsy specimens histologically and immunohistochemically. The specimens included cases of EPS (n = 12), suspected cases of EPS without later manifestation (n = 5), cases of infectious peritonitis (n = 20), cases of ultrafiltration failure (n = 25), and peritoneum at the start of peritoneal dialysis (n = 7). For each specimen, we evaluated these histologic parameters: fibrin deposition, mesothelial denudation, interstitial fibrosis, peritoneal fibroblast swelling, perivascular bleeding capillary angiogenesis, microvascular sclerosis, and interstitial mononuclear cell infiltration. We also evaluated these immunohistochemical markers: macrophage migration inhibitory factor (MIF), fibroblast growth factor (FGF), FGF receptor 2 (FGFR2), alpha smooth muscle actin (alpha SMA), MIB1, and BCL2. The most characteristic histologic findings for EPS were fibrin deposition and fibroblast swelling. The presence of capillary angiogenesis and mononuclear cell infiltration were also associated with EPS. Expression of FGF, FGFR2, MIF, MIB1, and BCL2 in peritoneal fibroblasts was frequently observed in EPS. Our results suggest that fibrin deposition and peritoneal fibroblast activation or proliferation (or both) are useful findings for the early diagnosis of EPS. Careful histologic observation of the peritoneal biopsy after withdrawal of peritoneal dialysis is required for the early diagnosis and prevention of EPS.