May also be called: Gastritis; Acute Gastritis; Chronic Gastritis Duodenitis is irritation and inflammation of the lining of the duodenum (the upper part of the small intestine). More to Know Food exits the stomach through the duodenum, a tube about a foot long that leads to the rest of the small intestine. Conditions that can cause irritation to the walls of the stomach or duodenum include overuse of some medications, alcohol, smoking, some diseases and conditions, abdominal injuries, and some bacterial and viral infections. Duodenitis can lead to peptic ulcers and cause abdominal pain, nausea, and vomiting. Keep in Mind Some causes of duodenitis disappear over time. Most cases of duodenitis can be treated effectively with medications or lifestyle and diet changes. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Indigestion Got tummy troubles? Indigestion is a common condition that many people - even kids - have at one time or another. Find out more in this article for kids. Read More Indigestion Indigestion is just another name for an upset stomach. It usually happens when people eat too much or too fast, or have foods that don't agree with them. Read More Peptic Ulcers Many people think that spicy foods cause ulcers, but the truth is that bacteria are the main culprit. Learn more about peptic ulcers. Read More Ulcers Doctors once thought that stress, spicy foods, and alcohol caused most stomach ulcers. But ulcers are actually caused by a particular bacterial infection, by certain medications, or from smoking. Read all about ulcers. Read More Helicobacter pylori H. pylori bacteria can cause digestive illnesses, including gastritis and peptic ulcer disease. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.