Common pathophysiologic changes associated with critical illness directly contribute to the development of gastrointestinal (GI) complications. In addition, supportive interventions such as mechanical ventilation and vasopressors increase the risk of GI complications. Early, specific signs of GI complications are rarely present; therefore, because of late or missed diagnosis, morbidity and mortality related to these complications can be high. This article aims to review the pathophysiology of GI dysfunction and describe an approach to evaluate the abdomen in the critically ill patient. Risk can be limited by understanding individual patient characteristics, thoughtfully evaluating the risk-benefit profile of all interventions, and implementing preventive strategies.