Abdominal pain: Pain in the belly (the abdomen). Abdominal pain can come from conditions affecting a variety of organs. The abdomen is an anatomical area that is bounded by the lower margin of the ribs above, the pelvic bone (pubic ramus) below, and the flanks on each side. Although abdominal pain can arise from the tissues of the abdominal wall that surround the abdominal cavity (the skin and abdominal wall muscles), the term abdominal pain generally is used to describe pain originating from organs within the abdominal cavity (from beneath the skin and muscles). These organs include the stomach, small intestine, colon, liver, gallbladder, and pancreas. Occasionally, pain may be felt in the abdomen even though it is arising from organs that are close to but not within the abdominal cavity, for example, the lower lungs, the kidneys, and the uterus or ovaries. This latter type of pain is called "referred" pain because the pain, though originating outside the abdomen, is being referred to (felt) in the abdominal area.
Abdominal pain can be acute and sudden in onset, or the pain can be chronic and longstanding. Abdominal pain may be minor and of no great significance, or it can reflect a major problem involving one of the organs in the abdomen. The characteristics of the pain--location, timing, duration, etc. are important in diagnosing its cause. Persistent or severe abdominal pain should be evaluated by a physician.
Acute abdominal pain may require urgent surgery such as for a twisted ovarian cyst, ectopic pregnancy, intestinal obstruction, appendicitis, peritonitis, perforated peptic ulcer, perforated diverticulitis, or abdominal aortic aneurysm. Patients with gallbladder disease, pancreatitis, or a kidney stone may also need urgent treatment. Acute or chronic abdominal pain may also call for medical (nonsurgical) therapy.
The causes of abdominal pain depend on sex and age of the patient. A woman may have a twisted ovarian cyst while a man may have testicular torsion with a twisted testis. Abdominal pain in infants and small children may be due to intestinal obstruction from atresia or stenosis of the intestine, esophageal webs, intussusception, volvulus, imperforate anus, and Hirschsprung disease. These causes of abdominal pain are rarely, if ever, encountered in adults.

Definition of Abdominal aneurysm

Abdominal aneurysm: An aneurysm
situated within the abdomen (belly). An aneurysm is a
localized widening (dilatation) of an artery, vein, or the
heart. At the area of an aneurysm, there is typically a
bulge and the wall is weakened and may rupture. The word
"aneurysm" comes from the Greek "aneurysma" meaning "a widening." An
aneurysm may involve the aorta, the largest artery in the body, as it
courses down through the abdomen. Because of the great volume of
blood flowing under high pressure in the aorta, rupture of an
abdominal aortic aneurysm is a surefire catastrophe.

Definition of Abdomen

Abdomen: The belly, that part of the body
that contains all of the structures between the chest and
the pelvis. The abdomen is separated anatomically from the chest
by the diaphragm, the powerful muscle spanning the body cavity below the lungs.
The abdomen includes a host of organs including the stomach, small intestine, colon, rectum, liver, spleen, pancreas, kidneys, appendix,
gallbladder, and bladder.
The word "abdomen" has a curious story behind it. It comes
from the Latin "abdodere", to hide. The idea was that whatever was
eaten was hidden in the abdomen.