Splenomegaly with splenic infarction or rupture: This condition is a common cause of left upper quadrant pain and could lead to a palpable mass or bulge due to the enlarged spleen. The spasm could be related to the peritoneal irritation.

Gastrointestinal issues (e.g., gastritis, peptic ulcer disease): These conditions can cause abdominal pain and spasm, potentially leading to a bulge if there is significant inflammation or if the patient is guarding (tensing abdominal muscles).
Constipation or fecal impaction: Severe constipation can lead to abdominal pain and a palpable mass in the left upper quadrant if the colon is impacted with feces.
Left kidney issues (e.g., pyelonephritis, kidney stone): Infections or obstructions of the left kidney can cause severe pain and potentially lead to a palpable mass if there is significant inflammation.

Ruptured abdominal aortic aneurysm: Although less common, a ruptured AAA can present with abdominal pain and a palpable mass. It's a medical emergency that requires immediate attention.
Ectopic pregnancy: In women of childbearing age, an ectopic pregnancy can cause severe abdominal pain and could potentially lead to a palpable mass if there is significant bleeding.
Splenic rupture due to trauma: This is a life-threatening condition that requires immediate surgical intervention.

Pancreatic pseudocyst: A complication of pancreatitis where a fluid collection forms in the pancreas, which can cause abdominal pain and a palpable mass.
Left adrenal gland tumor: Tumors of the adrenal gland can cause abdominal pain and a palpable mass, though they are relatively rare.
Diaphragmatic hernia: A hernia through the diaphragm can cause abdominal contents to move into the thoracic cavity, potentially leading to pain and a bulge in the left upper quadrant.