Pain in your upper left abdomen has many possible causes, including:

Inflammation of your pancreas, called pancreatitis
Pancreatic cancer
Enlarged spleen, called splenomegaly
Inflammation of your stomach lining, called gastritis
Stomach ulcer
Bile reflux
Stomach cancer
Kidney infection
Kidney stone

Pain in this part of your abdomen can also start in your chest because of:

Heartburn
Angina, or chest pain caused by coronary artery disease
Chest pain not related to your heart
Heart attack
Inflammation of the tissue that surrounds your heart, called pericarditis
Pneumonia
Inflammation of the lining of your lungs, called pleurisy
Pulmonary embolism

Abdominal Pain on Right Side

If you have pain in your lower right abdomen, it could mean trouble with your appendix, such as appendicitis or, rarely, appendix cancer.

You have some big organs on the upper right side of your abdomen, including your liver and right kidney, as well as your gallbladder. Serious causes of pain in this area include:

Hepatitis, including alcoholic hepatitis, toxic hepatitis, viral hepatitis, metabolic hepatitis, and autoimmune hepatitis
Gallstones
Liver disease, including liver cancer
Gallbladder cancer
Inflammation of your gallbladder, called cholecystitis
Kidney infection
Kidney stones
Duodenal ulcer
Large bowel obstruction