This retrospective cohort study was conducted at Tokai University Hachioji Hospital after being approved by the Institutional Review Board for Clinical Research at Tokai University. A total of 83 patients were diagnosed with perforation and penetration of the lower gastrointestinal tract from May 2010 to March 2019 and were treated with emergency surgery. Two cases for which abdominal computed tomography (CT) was not performed before surgery were excluded from this study. A further 17 cases in which the patient was diagnosed with lower digestive tract penetration from both preoperative abdominal CT and intraoperative findings were excluded from this study because they did not have panperitonitis and may not always be indicated for surgery. The remaining 64 cases were divided into a survival group and a non-survival (in-hospital mortality) group and analyzed.
Patient factors, preoperative factors, intraoperative factors, and postoperative courses are managed in a database. CT examinations performed preoperatively are stored in electronic medical records. Data from these sources were accessed for this study.
Patient and perioperative factors
Patient factors included age, sex, preoperative comorbidities, and body mass index (BMI). Preoperative factors included white blood cell count, C-reactive protein (CRP) concentration, albumin value, time from onset to surgery, Acute Physiology and Chronic Health Evaluation (APACHE) II score , and Sequential Organ Failure Assessment (SOFA) score . Intraoperative factors included operative time, blood loss, presence or absence of blood transfusion, cause of perforation, site of perforation, and operation method.
Body component analysis measurement
Abdominal CT images used in the diagnosis of lower gastrointestinal perforation before surgery were used to evaluate body composition. Abdominal CT was performed using an Aquilion ONETM platform (Canon Medical Systems, Tochigi, Japan). Psoas muscle mass, CT attenuation value of the psoas muscle, visceral fat area, and subcutaneous fat area were analyzed using a Ziostation2 Plus general-purpose diagnostic imaging workstation (Ziosoft, Tokyo, Japan). Each component was measured from horizontal cross-sections of the abdominal CT images. Psoas muscle area was traced as the region of interest (ROI) of the iliopsoas muscle contour at the level of the third lumbar vertebra (L3) (Fig. 1), and the sum of left and right areas was calculated. This area was then standardized as the psoas muscle index (PMI; in cm2/m2) by dividing the value by the square of height in meters. In addition, the CT attenuation value of the psoas muscle traced as described above was obtained to represent the variable of fat accumulation in psoas muscle that characterizes muscle atrophy, and the average of values for left and right muscles was taken as psoas muscle attenuation (PMA; in Hounsfield units). In the same manner, the areas of subcutaneous fat and visceral fat were calculated by measuring abdominal fat mass using the horizontal cross-section at the L3 level, and each area was then divided by the square of height in meters. With these standardizations, subcutaneous adipose tissue index (SATI; in cm2/m2) and visceral adipose tissue index (VATI; in cm2/m2) were determined, respectively. In addition, visceral-to-subcutaneous fat area ratio (VSR) was calculated as the visceral fat area divided by the subcutaneous fat area as an index of abdominal fat distribution. The receiver operating characteristic (ROC) curve was plotted for each variable, the optimal cut-off value for death due to lower gastrointestinal perforation was obtained via the Youden Index, and participants were assigned to the low-value or high-value group accordingly.
Postoperative multidisciplinary treatment
Postoperative multidisciplinary treatment was evaluated by the presence or absence of ventilatory management, blood purification (PMX-DHP), recombinant human soluble thrombomodulin (rTM) (Asahi Kasei Pharma Corporation, Tokyo, Japan), human anti-thrombin III , freeze-dried concentrated (hATIII) (Japan Blood Products Organization, Tokyo, Japan), and intravenous immunoglobulin (IVIg) (freeze-dried sulfonated human normal immunoglobulin; Teijin Pharma, Tokyo, Japan).
Data reflecting the postoperative course included DIC score on postoperative day 1, presence or absence of DIC on postoperative day 1, length of stay (LOS) in the intensive care unit (ICU) in days, duration until withdrawal of ventilatory support in days, postoperative complications, and postoperative stay in days. All postoperative complications were classified using the Clavien-Dindo classification (CD) , with CD3 or above defined as postoperative complications for the purposes of this study.
In the statistical analyses, comparisons between two groups were made using the Mann-Whitney test for continuous variables and either a c2 test or Fisher’s exact test (for any test involving a low number of samples) for categorical variables, with values of p < 0.05 regarded as significant. The determination of each cut-off was determined from the maximal Youden index for the ROC curve. Separate determinations were made for males and females, as muscle mass is significantly greater in males than in females regardless of age . To identify prognostic factors, univariate analysis was performed first, followed by multivariate analysis using all significant variables from univariate analysis. On univariate analysis, the Mann-Whitney test was used for continuous variables, and the Pearson c2 test for categorical variables. Multivariate analysis was performed using logistic regression. The software used for all statistical analyses was JMP for Windows version 13.0 (SAS Institute, Cary, NC).