All of the following structures form boundaries of Gastrinoma triangle EXCEPT:

Gastrinomas were originally assumed to arise in the pancreas, but most subsequent series have shown that the majority originate in the duodenum. Sixty percent to 90% are found in the so-called Gastrinoma triangle, an area in the upper pa of the abdomen. Superior point is at the junction of the cystic and common bile ducts. Its inferior point at the junction of the inferior margin of the second and third pas of the duodenum. It's left lateral point at the junction of the head and neck of the pancreas. The duodenum is the site of gastrinomas in more than 60% of patients, and there is a pronounced proximal-to-distal gradient within the duodenum (i.e., most are in the first pa, none in the fouh).