Original ArticlesPrevalence and Clinicopathologic Features of Intestinal Perforation Caused by Segmental Absence of the Intestinal Musculature in AdultsTsuyuki, Takuji MD*; Satou, Akira MD, PhD*; Takahara, Taishi MD, PhD*; Nakajima, Kosei MD, PhD†; Tsuzuki, Toyonori MD, PhD*Author Information *Department of Surgical Pathology, Aichi Medical University Hospital, Nagakute †Department of Surgical Pathology, Ichinomiya Municipal Hospital, Ichinomiya, Japan Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Toyonori Tsuzuki, MD, PhD, Department of Surgical Pathology, Aichi Medical University Hospital, 1-1, Yazakokarimata, Nagakute 480-1195, Japan (e-mail: [email protected]). The American Journal of Surgical Pathology: June 2021 - Volume 45 - Issue 6 - p 803-811 doi: 10.1097/PAS.0000000000001671 Buy Metrics Abstract Segmental absence of the intestinal musculature (SAIM) can cause intestinal perforation in adults. However, its prevalence and clinicopathologic features have not been well-described. This study aimed to determine the prevalence of SAIM-associated perforation and characterize its clinicopathologic features. We retrospectively examined 109 cases of intestinal perforation that underwent surgical resection from January 2009 to December 2019. SAIM was defined as the complete absence of the muscularis propria without extensive inflammation and fibrinous exudation around the perforation. SAIM was the second most frequent cause of perforation (26 cases: 24%), the most frequent cause being related to diverticulitis (39 cases: 36%). The most common site was the sigmoid colon (12 cases: 46.2%). The younger group (aged below 65 y) exhibited more frequent perforation of the upper segments of the gastrointestinal tract (from the duodenum to the descending colon) than the older group (65 y and above) (P=0.0018). No patients developed recurrence. The most common gross features were well-defined circular or small punched-out lesions, and the histologic features were complete absence of the muscularis propria and absence of hemorrhage and necrosis around the area of perforation. The characteristic features of SAIM were unique and their prevalence was higher than previously reported. The precise recognition of SAIM can aid in understanding the cause of perforation and avoiding further unnecessary examinations. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.