Illustration of the digestive organs of the body. At front is the stomach, behind it is the pancreas (yellow), and the small (pink) and large (brown) intestines. The stomach's lining is inflamed, a condition known as gastritis. Gastritis may cause abdominal pain, nausea, vomiting, bloating, loss of appetite or heartburn. Untreated gastritis can lead to stomach ulcers or tumours.