 Introduction/Background According to the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3), sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection [1]. Therefore, what differentiates sepsis from simple infection is the presence of an aberrant host response to the underlying infection and the presence of organ dysfunction. When unexplained organ dysfunction is present, a search for possible causes of infection should commence, and radiological imaging is an integral part of this investigation. In 2017, the global incidence of sepsis was estimated to be 48.9 million cases with 11 million sepsis-related deaths (accounting for nearly 20% of all global deaths) [2]. Within the United States, according to the Centers for Disease Control and Prevention, the incidence of sepsis is >1.7 million adults per year. Greater than 15% of Americans diagnosed with sepsis die as a result of sepsis each year, and the in-hospital mortality is >30%, exemplifying that prompt recognition and treatment is crucial. Furthermore, sepsis was shown to account for 5.2% of total United States hospital costs (>20 billion dollars) in 2011, and the incidence is only rising because of an aging population [3,4]. Risk factors for the development of sepsis overlap with risk factors for infection and include immune compromise, chronic diseases such as malignancy, certain patient demographics (infants and elderly persons, males, Black race), as well as numerous unidentified causes [5]. This ACR Appropriateness Criteria on Sepsis focuses on thoracic and abdominopelvic causes of sepsis. Other causes of sepsis such as osteomyelitis, diabetic foot infections, periprosthetic infections, and cardiovascular infections (including endocarditis and those due to implantable devices) are not addressed. OR aPortland VA Healthcare System and Oregon Health & Science University, Portland, Oregon. bOregon Health & Science University, Portland, Oregon.
Sepsis.  Introduction/Background According to the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3), sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection [1]. Therefore, what differentiates sepsis from simple infection is the presence of an aberrant host response to the underlying infection and the presence of organ dysfunction. When unexplained organ dysfunction is present, a search for possible causes of infection should commence, and radiological imaging is an integral part of this investigation. In 2017, the global incidence of sepsis was estimated to be 48.9 million cases with 11 million sepsis-related deaths (accounting for nearly 20% of all global deaths) [2]. Within the United States, according to the Centers for Disease Control and Prevention, the incidence of sepsis is >1.7 million adults per year. Greater than 15% of Americans diagnosed with sepsis die as a result of sepsis each year, and the in-hospital mortality is >30%, exemplifying that prompt recognition and treatment is crucial. Furthermore, sepsis was shown to account for 5.2% of total United States hospital costs (>20 billion dollars) in 2011, and the incidence is only rising because of an aging population [3,4]. Risk factors for the development of sepsis overlap with risk factors for infection and include immune compromise, chronic diseases such as malignancy, certain patient demographics (infants and elderly persons, males, Black race), as well as numerous unidentified causes [5]. This ACR Appropriateness Criteria on Sepsis focuses on thoracic and abdominopelvic causes of sepsis. Other causes of sepsis such as osteomyelitis, diabetic foot infections, periprosthetic infections, and cardiovascular infections (including endocarditis and those due to implantable devices) are not addressed. OR aPortland VA Healthcare System and Oregon Health & Science University, Portland, Oregon. bOregon Health & Science University, Portland, Oregon.