**Core Concept**
Pancreatic pseudocysts are fluid collections that form in the pancreas as a result of pancreatitis or pancreatic trauma. They can be managed conservatively or surgically, depending on their size, location, and symptoms.

**Why the Correct Answer is Right**
After 3 weeks of duration, a pancreatic pseudocyst that is 5cm in size is considered mature and has a lower risk of rupture or infection. The management of choice for such a pseudocyst is **surgical drainage**, which involves creating a communication between the pseudocyst and the stomach or small intestine to allow for gradual drainage of the fluid. This approach is favored over percutaneous drainage or conservative management, as it reduces the risk of complications and promotes healing.

**Why Each Wrong Option is Incorrect**
**Option A:** **Conservative management** is not recommended for a pseudocyst of this size and duration, as it may lead to complications such as rupture or infection.
**Option B:** **Percutaneous drainage** may be considered for smaller pseudocysts or those that are causing symptoms, but it is not the preferred method for a mature pseudocyst of this size.
**Option C:** **Endoscopic drainage** is a minimally invasive technique that can be used for smaller pseudocysts, but it may not be effective for a pseudocyst of this size and may require multiple procedures.

**Clinical Pearl / High-Yield Fact**
The management of pancreatic pseudocysts should be individualized based on the size, location, and symptoms of the pseudocyst, as well as the patient's overall clinical condition.

**Correct Answer:** C. Endoscopic drainage.