Acute mesenteric ischemia is an abdominal emergency because reduced blood flow to bowel loops rapidly leads to irreversible necrosis and death. This paper reviews the different conditions (arterial, venous, low-flow states) that can result in reduced blood flow to bowel loops. Since the clinical and laboratory findings are nonspecific, imaging tests play an important role in the diagnosis of mesenteric ischemia. Multidetector computed tomography is the first-choice technique for the initial workup in cases of suspected acute mesenteric ischemia because it can rule out other causes of acute abdominal pain. It is important to know the characteristic radiological signs of this entity, because early diagnosis is essential to prevent progression to life-threatening intestinal necrosis.