Investigation of case findings for sarcopenia using comparative measurements of the iliopsoas muscle and rectus abdominis on CT

Abstract

Background Sarcopenia is considered to be a major factor in frailty, and early detection of sarcopenia is important to prevent frailty. Weakness of the lower abdominal region (WLAR) is one of the findings in Kampo (Traditional Japanese) medicine that indicates a condition similar to sarcopenia. We hypothesized that there may be a correlation between the iliopsoas (psoas) muscle and the rectus abdominis. In this study, we used measurements taken from computed tomography (CT) scans of the iliopsoas muscle and rectus abdominis, and investigated which measurements of abdominal muscle indices are relevant to a diagnosis of sarcopenia. Method The subjects were 100 consecutive patients (50 males and 50 females) who were treated in our department. We collected their age, height, weight, body mass index (BMI), and WLAR findings, which were divided into three levels: f(0): no WLAR, f(1): suspected WLAR and f(2): obvious WLAR. We also measured CT images of iliopsoas and rectus abdominis muscle-related indices and the psoas muscle index (PMI) was calculated. Results The correlation coefficient between the rectus abdominis data obtained from multiple regression analysis and the PMI was R2 = 0.36 or higher for both females and males, indicating that the size of the iliopsoas muscle can be predicted from measurements of the rectus abdominis muscle. In both females and males, this suggests that sarcopenia groupings determined by the PMI in the iliopsoas muscle are consistent with groupings based on WLAR. The length of the rectus abdominis muscle was measured, and the mean of each of the three WLAR groups showed significant differences in upper rectus abdominis muscle dehiscence and lower rectus abdominis muscle dehiscence in females. In males, there were significant differences in muscle dehiscence only of the upper rectus abdominis. Discussion It is known from previous reports that the iliopsoas muscle is an indicator of sarcopenia. This study suggests that the rectus abdominis muscle might also be an indicator of sarcopenia based on the relationship between the measured values of the iliopsoas and rectus abdominis muscles. When the cutoff values identified with the PMI were applied, significant differences were found among the groups based on PMI and WLAR values, which are currently used for diagnosis. These results suggest that WLAR may provide a useful way of screening case findings for sarcopenia. Conclusion In this study, we were able to identify positive correlations between the rectus abdominis and iliopsoas muscles by obtaining measurements from CT images. Our results indicate that the status of the rectus abdominis might be used in the diagnosis of sarcopenia.