Marginal Ulcer: This is a common complication following gastric bypass surgery, especially if the patient has a history of ulcer disease or is using nonsteroidal anti-inflammatory drugs (NSAIDs). The burning abdominal pain is consistent with ulcer symptoms.

Gastroesophageal Reflux Disease (GERD): Although gastric bypass surgery can reduce symptoms of GERD, some patients may still experience reflux, leading to burning abdominal pain.
Stomal Stenosis or Narrowing: This complication can cause abdominal pain, nausea, and vomiting. The burning sensation could be related to the narrowing of the stoma.
Intestinal Obstruction: Partial or complete obstruction of the intestine can cause abdominal pain, which might be described as burning, especially if there is associated inflammation.

Leak from the Gastrojejunostomy: A leak is a serious and potentially life-threatening complication that requires immediate attention. While it might not be the first consideration for burning abdominal pain, it's crucial not to miss it due to its severity.
Bowel Ischemia: Reduced blood flow to the bowel can cause severe abdominal pain and is a medical emergency. The pain might be burning in nature, especially if there's associated inflammation or necrosis.

Celiac Axis Stenosis or Occlusion: This is a rare complication that can occur after gastric bypass surgery, leading to chronic abdominal pain due to insufficient blood supply to the stomach and other organs.
Chronic Mesenteric Ischemia: Although more commonly associated with atherosclerotic disease, it could potentially occur in the post-surgical setting, especially if there were complications during surgery affecting blood flow to the intestines.