Sarcopenia refers to reduced muscle mass in the elderly population, and this malady is of great interest in clinical course, including postoperative complications and mortality when treating major cancer in the elderly. The definition of sarcopenia varies according to the method of measuring muscle mass, and the skeletal muscle index (SMI) tends to be extensively used in retrospective studies. In many reports, sarcopenia has been reported to be a poor prognostic factor after gastrectomy, colectomy, pancreatectomy and liver transplantation, with regards to complications and the length of the hospital stay. Additionally, patients suffering from sarcopenia have a higher medical burden due to their poor clinical outcome after surgery. To overcome these difficulties, nutritional support and exercise training to improve sarcopenia before surgery is helpful, and so further studies that focus on these treatments need to be conducted.

Sarcopenia is characterized as a syndrome involving the progressive or generalized loss of skeletal muscle mass and strength with or without increased fat mass. This is one of well-known risk factors for adverse treatment outcomes in patients with various medical and surgical diseases. Sarcopenia itself, independent of the body mass index, is a powerful prognostic factor for cancer cachexia, liver cirrhosis, and even all causes of mortality. In terms of gastrointestinal surgery, sarcopenia is a significant prognostic factor in patients with gastric or colorectal cancers. Sarcopenia is related to postoperative complication, 30-day mortality, overall survival, and disease-free survival after gastrointestinal surgery. For patients with hepatic surgery, sarcopenia is also a significant prognostic factor. Several studies, including meta-analysis, proved sarcopenia to be waiting-list mortality and post-transplantation mortality in liver transplantation patients. Similarly, preoperative sarcopenic obesity was an independent risk factor for death and hepatocellular carcinoma recurrence after a hepatectomy. In cases of pancreatic cancer, several studies proposed that sarcopenia was an objective measure of patient frailty that was strongly associated with the long-term outcome independent of tumor-specific factors. In addition, sarcopenia or sarcopenic obesity has been reported to be a strong predictor of major complications after pancreatectomy. As a result, sarcopenia could be used to improve patient selection before a pancreatectomy. The next step to solve the questions to manage sarcopenia and improve the post-pancreatectomy outcomes would be to determine the role of nutrition and physical activity in the prevention or treatment of sarcopenia, and to develop specific medications with an evidence-based treatment of sarcopenia in patients with pancreatectomy.

Sarcopenia, which is defined as a decrease in skeletal muscle mass and strength with aging, is an important risk factor in clinical medicine that is associated with mortality, and poor surgical and nonsurgical outcomes. Sarcopenia is now recognized as a multifactorial geriatric syndrome. Cachexia is defined as a metabolic syndrome with inflammation as the key feature, so cachexia can be an underlying condition of sarcopenia. Recently, cachexia has been defined as a complex metabolic syndrome associated with an underlying illness and characterized by the loss of muscle mass with or without a loss of fat mass. These two conditions overlap but are not the same. In clinical practice, many factors related to sarcopenia (decreased food intake, inactivity, and decreased hormones) are reported frequently in patients with cachexia. On the contrary, systemic inflammation, the core feature of cachexia, can also be present in apparently healthy older sarcopenic patients. This suggests that new therapeutic approaches, alone or in combination, may be appropriate in both conditions.

Accurate measurement of body composition between lean and adipose tissue mass and distribution of lipid burden may be important in the care of nutritional problems in patients observed in clinical practice and the measurement of outcomes in clinical research. In this review, we discuss the most accurate imaging methods for use as clinical tools in measurement of body composition and distribution. Dual-energy x-ray absorptiometry (DXA) is a non-invasive technique for assessment of body composition, and the radiation exposure is relatively minimal. However, measurements are influenced by thickness of tissue and lean tissue hydration. Computed tomography (CT) is a gold-standard imaging method for body composition analysis at the tissue-organ level, however the radiation generated by the CT scan is relatively high, thus it should not be considered for a measurement, which can be repeated frequently. Magnetic resonance imaging (MRI) has been a useful modality in the assessment of body composition changes in various clinical studies. However, limitations of MRI for assessment of body composition are related to its high cost and technical expertise necessary for analysis. Proper methods for measurement of body composition in specific medical situations like sarcopenia should be evaluated for determination of comparative validity and accuracy, within the context of cost-effectiveness in patient care. In conclusion, an ideal body imaging method would have a significant utility for earlier detection of nutritional risks, while overcoming the limitations of current imaging studies such as DXA, CT, and MRI.