The purpose of this study is to define the natural history and causes of chronic critical illness (CCI) in surgical intensive care patients who have had sepsis. The investigator wants to study a sub-population of sepsis patients that have intra-abdominal sepsis. The purpose of this research study is to define the acute changes in frailty (weakness, slowness, loss of muscle mass), comorbidity (medical problems) and disability (difficulty with mobility and performing routine daily functions) after having an infection that is located in the abdominal cavity or torso. The investigator believes having severe infection contributes to acute and permanent changes in these areas, especially in those of advanced age.