Background It is estimated there were 3.45 million new cases and 1.75 million deaths from cancer in Europe in 2012. Colorectal cancer was one of the most common, accounting for 13% of new cases and 12.2% of all deaths. Conditions causing reduced muscle mass, such as sarcopenia, can increase the morbidity and mortality of people with cancer. Computed tomography (CT) scans can provide accurate, high quality information on body composition including muscle mass. To date, there has been no systematic review on the role of CT scans in identifying sarcopenia in abdominal cancer. This review aimed to examine the role of CT scans indetermining the influence of reduced muscle mass on clinical outcome in abdominal cancer. Methodology A systematic review of English-language articles published in 2000 or later was conducted. Articles included cohort, randomised controlled trials and validation studies. Participants were people diagnosed with abdominal cancer who had undergone a CT scan. Data extraction and critical appraisal was undertaken. Results Ten cohort studies met the inclusion criteria. Seven demonstrated that low muscle mass was significantly associated with poor clinical outcome, with six specifically demonstrating reduced survival rates. Eight studies demonstrated that a greater number of patients (27.3-66.7%) were identified as sarcopenic using CT scans compared to numbers identified as malnourished using Body Mass Index (BMI). Conclusion CT scans can identify reduced muscle mass and predict negative cancer outcomes in people with abdominal malignancies, where traditional methods of assessment are less effective.