 Introduction/Background Upper gastrointestinal (GI) bleeding (UGIB) refers to bleeding occurring proximal to the ligament of Treitz, from the esophagus, stomach, or duodenum [1,2]. The incidence of nonvariceal UGIB is almost 5 times higher than that of variceal UGIB [1]. Peptic ulcer disease caused by Helicobacter pylori infection or nonsteroidal anti-inflammatory drug use is the most common cause of nonvariceal UGIB. The other causes of nonvariceal UGIB include Mallory- Weiss tears, esophagitis, pancreatitis, trauma, iatrogenic, or neoplastic [1]. Some rare causes of nonvariceal UGIB include hemobilia, hemosuccus pancreaticus, and aortoenteric fistula [3,4]. UGIB frequently presents with hematemesis or melena. However, a minority of patients can present with hematochezia [2]. GI bleeding (GIB) is either overt or occult. Patients with overt GIB present with signs of visible bleeding such as hematemesis, hematochezia, or melena. Patients with occult GIB have guaiac-positive stools or iron deficiency anemia, without visible blood loss. Obscure GIB refers to bleeding with unknown source despite complete GI tract imaging and endoscopic evaluation [2,5]. Clinically, obscure GIB can be overt (manifests as continued passage of visible blood) or occult (no visible blood). Special Imaging Considerations Multiphase CT is used in the evaluation of patients with overt GIB, including noncontrast, late arterial, and venous phases of contrast administration [5]. With dual-energy CT, virtual noncontrast images can replace a true noncontrast acquisition [11]. Because the virtual noncontrast images are derived from the contrast-enhanced data set, these images are perfectly aligned, which can aid interpretation. The conspicuity of active GIB can also be increased by the use of low-keV virtual monoenergetic or iodine-only images [12]. In a study on the use of dual- energy CT imaging for patients presenting with clinical overt GIB, dual-energy CT images improved the radiologist
Nonvariceal Upper Gastrointestinal Bleeding.  Introduction/Background Upper gastrointestinal (GI) bleeding (UGIB) refers to bleeding occurring proximal to the ligament of Treitz, from the esophagus, stomach, or duodenum [1,2]. The incidence of nonvariceal UGIB is almost 5 times higher than that of variceal UGIB [1]. Peptic ulcer disease caused by Helicobacter pylori infection or nonsteroidal anti-inflammatory drug use is the most common cause of nonvariceal UGIB. The other causes of nonvariceal UGIB include Mallory- Weiss tears, esophagitis, pancreatitis, trauma, iatrogenic, or neoplastic [1]. Some rare causes of nonvariceal UGIB include hemobilia, hemosuccus pancreaticus, and aortoenteric fistula [3,4]. UGIB frequently presents with hematemesis or melena. However, a minority of patients can present with hematochezia [2]. GI bleeding (GIB) is either overt or occult. Patients with overt GIB present with signs of visible bleeding such as hematemesis, hematochezia, or melena. Patients with occult GIB have guaiac-positive stools or iron deficiency anemia, without visible blood loss. Obscure GIB refers to bleeding with unknown source despite complete GI tract imaging and endoscopic evaluation [2,5]. Clinically, obscure GIB can be overt (manifests as continued passage of visible blood) or occult (no visible blood). Special Imaging Considerations Multiphase CT is used in the evaluation of patients with overt GIB, including noncontrast, late arterial, and venous phases of contrast administration [5]. With dual-energy CT, virtual noncontrast images can replace a true noncontrast acquisition [11]. Because the virtual noncontrast images are derived from the contrast-enhanced data set, these images are perfectly aligned, which can aid interpretation. The conspicuity of active GIB can also be increased by the use of low-keV virtual monoenergetic or iodine-only images [12]. In a study on the use of dual- energy CT imaging for patients presenting with clinical overt GIB, dual-energy CT images improved the radiologist