A duodenal ulcer is an open sore in the lining of the duodenum, the first part of the small intestine, that lies immediately distal (after) the stomach. The broad term for ulceration in the stomach or duodenal lining is peptic ulcer disease. Most of the causes of stomach ulcers are also responsible for the development of duodenal ulcers.
The duodenum has an inner epithelial lining, known as the mucosa. It is made up of simple columnar cells and also contains specialized cells that produce mucus and a few digestive enzymes. With duodenal ulcers, the mucosa is eroded revealing the underlying layers like the submucosa and in severe cases, an ulcer may perforate the duodenal wall. Duodenal ulcers are more common than stomach ulcers and are usually a solitary (single) ulcer. The ulcer usually forms close to the pyloric valve and more often occurs on the anterior duodenal wall.
The duodenum has its own protective mechanisms against gastric acid in addition to a mucus barrier like the stomach. When acidity is detected in the duodenum, the pancreatic ducts secrete a combination of water and bicarbonate ions to neutralize the gastric acid in the duodenum. Digestive hormones like secretin are also released into the blood stream to slow down gastric emptying thereby allowing the duodenum to cope with smaller quantities of gastric acid. The epithelial cells can also actively pump out hydrogen ions from the duodenal lumen, further reducing the acid content.
Causes of Duodenal Ulcers
A duodenal ulcer arises when the protective mechanisms that protect the epithelial lining are compromised. The incoming acidic chyme from the stomach can erode the lining of the duodenum. The most common causes of duodenal ulcers, like stomach ulcers, include H.pylori infection and the use of NSAIDs.
- Helicobacter pylori (H.pylori) Infection
- H.pylori is a type of bacteria that infects the stomach lining but may also extend to the duodenum especially if the duodenal mucosa is altered in a manner that it resembles the stomach lining (gastric metaplasia).
- H.pylori increases gastric acid secretion in the stomach and also degrades the mucus barrier.
- This allows gastric acid to make contact with the duodenal lining, leading to inflammation and eventually ulceration.
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- NSAIDs are widely available drugs used to reduce inflammation and ease pain.
- These drugs impair the mucus barrier of the duodenum thereby allowing gastric acid to make contact with the duodenal lining.
- Chronic use of NSAIDs are more likely to lead duodenal ulceration.
Other factors may also contribute to ulceration by either significantly increasing gastric acid secretion or compromising the mucus barrier protecting the duodenum. This includes :
- Cigarette smoking
- Alcohol misuse
- Advancing age, especially if there is a history of H.pylori infection
- Severe illness and debilitated patients
- Ingestion of caustic agents
- Hyperacidity conditions like Zollinger-Ellison syndrome
- Epstein-Barr virus (EBV), cytomegalovirus (CMV) or herpes simplex virus-1 (HSV-1)
- Family history
- Chemotherapy and radiation therapy in cancer patients