Which of the following is the most common location for peptic ulcers in the duodenum?

Explanation

## Location of Duodenal Ulcers **Key Point:** The **anterior wall of the first part of the duodenum (D1)** is the most common site for duodenal ulcers, accounting for the majority of all duodenal ulcers. ### Anatomical Significance The anterior wall of D1 is the most frequently affected site because: - It is the first segment exposed to acidic gastric contents entering the duodenum - The anterior wall is the classic site for **perforation** into the peritoneal cavity (free air under the diaphragm on erect CXR) - Approximately 95% of all duodenal ulcers occur in D1, with the anterior wall being the predominant location ### Clinical Pearl **Anterior wall D1 ulcers** are the most common duodenal ulcers overall and classically perforate into the peritoneal cavity, presenting with sudden-onset severe epigastric pain and peritonitis. **Posterior wall D1 ulcers**, while less common, are clinically significant because they can erode into the **gastroduodenal artery (GDA)**, causing life-threatening hemorrhage. ### Distribution Pattern | Location | Frequency | Clinical Significance | |----------|-----------|----------------------| | D1 anterior wall | Most common | Risk of perforation into peritoneum | | D1 posterior wall | Less common | Risk of GDA erosion and hemorrhage | | D2–D3 | Rare (~2%) | Associated with Zollinger-Ellison syndrome | **High-Yield (Robbins / Harrison):** D1 anterior wall = most common site; D1 anterior = perforation risk; D1 posterior = bleeding risk (GDA erosion). Remember: "Anterior perforates, Posterior bleeds."