There are many reasons why there may be pain in the upper abdomen, both mild and serious. These may involve the stomach and the digestive tract, although problems in several other organs can lead to pain in the upper abdomen.

Stomach and Digestive

Problems directly relating to the digestive system which may cause upper stomach pain include, according to the Mayo Clinic, indigestion, peptic ulcer, bowel (intestinal) obstruction, too little blood flow to the intestines (mesenteric ischemia), GERD (chronic acid reflux) and, in infants, pyloric stenosis, a problem stops food from entering the small instestine.

Lungs

Problems in the lungs can also lead to pain in the upper abdomen, according to the Mayo Clinic. These include pleurisy (the swelling of the membrane around the lungs), pneumonia and a collapsed lung.

Heart

Heart problems such as angina (too little blood flowing to the heart), an aneurysm in the aorta (a large blood vessel that supplies much of the lower body), pericarditis (the swelling of the covering of the heart) or heart attack, according to the Mayo Clinic.

Other Organs

Appendicitis (which causes the appendix to swell and fill with pus), cholangitis (swelling in the bile duct), duodenitis (swelling of part of the small intestine known as the duodenum), gallstones, hepatitis and pancreatitis (swelling of the pancreas) can also cause upper abdominal pain, according to the Mayo Clinic.

Cancer

Non-Hodgkins lymphoma may be a cause of upper abdominal pain, according to the Mayo Clinic. However, Medline Plus notes that this is uncommon.

Warning

The Mayo Clinic recommends seeking immediate treatment, if you have are other symptoms like chest pain or pressure, the pain is so bad you cannot find a comfortable position, you notice blood in the stool, have nausea and vomiting that won't go away, yellowing of the skin or if your abdomen is swollen and tender.

Source:

Mayo Clinic: Abdominal Pain Causes

Medline Plus: Abdominal Pain

Mayo Clinic: Abdominal Pain: When to See a Doctor