Gastroesophageal Reflux Disease (GERD) with Esophagitis: This condition is a common cause of vomiting blood due to the erosion of the esophageal lining, leading to bleeding. The frequent exposure of the esophagus to stomach acid can cause inflammation and ulcers, which may bleed.

Peptic Ulcer Disease: Both gastric and duodenal ulcers can cause bleeding, leading to vomiting blood. The use of NSAIDs, Helicobacter pylori infection, and stress are common risk factors.
Gastritis: Inflammation of the stomach lining can lead to erosion and bleeding. Causes include alcohol use, NSAIDs, stress, and infections.
Mallory-Weiss Syndrome: This condition involves tears in the mucous membrane or lining of the lower end of the esophagus, where it connects to the stomach. These tears can bleed, and the blood may be vomited up.

Esophageal Varices: These are enlarged veins in the esophagus that can bleed easily due to increased pressure from the liver. This condition is often associated with liver cirrhosis and portal hypertension. Missing this diagnosis can be fatal due to the high risk of severe bleeding.
Aortic Enteric Fistula: Although rare, this condition involves a fistula (abnormal connection) between the aorta and the gastrointestinal tract, which can lead to massive bleeding.
Cancer of the Esophagus or Stomach: Tumors in the esophagus or stomach can cause bleeding, which may be vomited. Early detection is crucial for treatment and prognosis.

Dieulafoy's Lesion: A rare cause of gastrointestinal bleeding characterized by a small, superficial ulceration with an exposed, often large, caliber artery at its base.
Hemobilia: Bleeding from the bile ducts into the gastrointestinal tract, which can be due to trauma, tumors, or vascular malformations.
Angiodysplasia: Vascular malformations of the gastrointestinal tract that can cause bleeding. They are more common in the elderly and can be associated with other systemic diseases.