**Core Concept**
Pancreatic pseudocysts are fluid collections that develop in the abdomen due to pancreatic trauma, inflammation, or other pathologies, often resulting from pancreatic duct disruption or obstruction. The common complications of pancreatic pseudocysts arise from their potential to cause mechanical obstruction, infection, or rupture.

**Why the Correct Answer is Right**
The most common complication of pancreatic pseudocysts is infection, which can lead to abscess formation and sepsis. This is due to the pseudocyst's potential to become secondarily infected by bacteria, leading to significant morbidity and mortality. The risk of infection increases with the size and duration of the pseudocyst, as well as the presence of a communication with the pancreatic duct. The infection can also lead to the formation of an abscess, which requires urgent drainage.

**Why Each Wrong Option is Incorrect**
**Option A:** Rupture is a potential complication of pancreatic pseudocysts, but it is less common than infection. Rupture can lead to severe abdominal pain, hemorrhage, and peritonitis.
**Option B:** Mechanical obstruction is another potential complication, but it is not the most common one. Obstruction can occur due to the pseudocyst pressing on adjacent structures, such as the duodenum or stomach.
**Option C:** Hemorrhage is a rare complication of pancreatic pseudocysts, often resulting from erosion into adjacent blood vessels. While it is a serious complication, it is not the most common one.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate between pancreatic pseudocysts and true cysts, as the management strategies differ significantly. Pancreatic pseudocysts are typically managed conservatively, while true cysts often require surgical resection.

**Correct Answer: C. Rupture is a potential complication of pancreatic pseudocysts, but it is less common than infection. Rupture can lead to severe abdominal pain, hemorrhage, and peritonitis.