**Core Concept:** Pseudocysts are fluid-filled collections of fluid that develop as a complication of acute or chronic pancreatitis. They form as a result of inflammation and necrosis of the pancreas, leading to disruption of the pancreatic duct and accumulation of pancreatic enzymes and fluid.

**Why the Correct Answer is Right:** The complication least likely to occur in a pseudocyst of the pancreas is a pancreatic pseudocyst rupture into the peritoneum (option D). This is because pseudocysts are typically well-capsulated and surrounded by a dense fibrous layer that protects them from rupturing. In contrast, rupture into the gastrointestinal tract or retroperitoneum is more common due to the thin-walled nature of these structures.

**Why Each Wrong Option is Incorrect:**

A. Hemorrhage (option C) is a complication of acute pancreatitis, not pseudocysts. Pseudocysts are encapsulated collections of pancreatic secretions and do not bleed.

B. Infection (option B) is a complication of both acute and chronic pancreatitis, and can occur in pseudocysts. However, the correct answer is less likely due to the fact that pseudocysts are encapsulated and have a protective layer.

**Clinical Pearl:** When evaluating a patient with a pancreatic pseudocyst, it is essential to consider the differential diagnosis of rupture into adjacent structures and complications like infection and hemorrhage. However, when selecting the least likely complication, the protective capsule of a pseudocyst makes rupture into the peritoneum the least likely compared to rupture into the gastrointestinal tract or retroperitoneum.