**Core Concept**
A cystogastrostomy is a surgical procedure that involves creating a communication between a pancreatic pseudocyst and the stomach. The procedure is often performed to treat complications associated with pancreatic pseudocysts, such as abdominal pain, weight loss, or intestinal obstruction. The major complications of this procedure are related to the potential for leakage of pancreatic enzymes into the stomach, leading to severe abdominal pain, infection, and potentially life-threatening consequences.

**Why the Correct Answer is Right**
The major complication of cystogastrostomy for pancreatic pseudocyst is **infection and peritonitis** due to leakage of pancreatic enzymes into the stomach. This occurs when the communication between the pseudocyst and the stomach fails to seal properly, allowing pancreatic juice to leak into the peritoneal cavity. The infection can spread rapidly, leading to severe abdominal pain, fever, and potentially septic shock. The leakage of pancreatic enzymes can also cause necrotizing pancreatitis, a life-threatening condition that requires immediate surgical intervention.

**Why Each Wrong Option is Incorrect**
**Option A:** Pancreatic cancer is not a direct complication of cystogastrostomy for pancreatic pseudocyst, although it can be a comorbidity in some patients.

**Option B:** Intestinal obstruction is not a major complication of cystogastrostomy, although it can occur if the procedure is not performed correctly.

**Option C:** Pancreatic fistula is a possible complication of cystogastrostomy, but it is not the most severe or major complication associated with this procedure.

**Clinical Pearl / High-Yield Fact**
To minimize the risk of complications, it is essential to carefully evaluate the patient's anatomy and the pseudocyst's characteristics before performing a cystogastrostomy. The procedure should be performed by an experienced surgeon who can minimize the risk of leakage and infection.

**Correct Answer:** C. Pancreatic fistula is a possible complication of cystogastrostomy, but it is not the most severe or major complication associated with this procedure.