In gastric outlet obstruction in a peptic ulcer patient, the site of obstruction is most likely to be -

"The term 'pyloric stenosis' is a misnomer. The stenosis is seldom at the pylorus. Commonly, when the condition is due to underlying peptic ulcer disease, the stenosis is found in the first pa of the duodenum, the most common site for a peptic ulcer." Also, know There are 2 common causes of gastric outlet obstruction pyloric stenosis secondary to peptic ulcer gastric cancer Earlier peptic ulcer was the most common cause, but now the most common cause of gastric outlet obstruction is - gastric cancer. Ref : Bailey & Love 25/e p1065