Background/Purpose: P-selectin promotes adherence of leukocytes to the endothelium in inflammatory processes. The aim of this study was to investigate the expression of P-selectin and its role in the development of inflammation in neonates with necrotizing enterocolitis (NEC).Methods: Twenty-nine intestinal specimens from 13 neonates with NEC and 7 control neonates with congenital gastrointestinal abnormalities were studied. Histologic damage, immumohistochemical expression of P-selectin, and polymorphonuclear cell infiltrate were graded blindly. Mann-Whitney U and Spearman rank tests were used to compare grades.Results: Expression of P-selectin was increased in NEC compared with controls in both medium-sized vessels (P = .03) and in the microcirculation (P = .03). P-selectin expression on medium-sized vessels correlated with the degree of histologic injury (P = .02, r = 0.425). P-selectin expression was greatest in areas of active inflammation but markedly lower in necrotic areas. The degree of polymorphonuclear cell infiltration strongly correlated with P-selectin expression on both medium-sized vessels (P = .004, r = 0.513) and the microcirculation (P = .001, r = 0.578).Conclusions: Expression of P-selectin is increased in medium-sized vessels and in the microcirculation in intestinal specimens of neonates with NEC compared with neonatal controls. Expression of P-selectin is associated with the recruitment of polymorphonuclear cells and the severity of histologic injury, although P-selectin expression is lost in necrotic tissue. (c) 2005 Elsevier Inc. All rights reserved.