The abdomen refers to the cavity in the mid-portion of the body bounded superiorly by the diaphragm that separates it from the thorax. The abdomen contains a number of organs including the pancreas, stomach, intestines, liver, spleen, bladder, and gallbladder.

The abdominal cavity is the largest cavity in the human body. It is somewhat oval in shape, with the long axis of the oval running upward and downward. There is a flaring out of the abdomen from bottom to top. The abdomen more accurately resembles an egg, with the narrower region of the oval pointing down. Variation in the size of the abdomen occurs with age and sex. The abdomen of an adult male tends to be oval but flattened in the front. In the adult female the oval shape tends to be narrower to accommodate the larger pelvic region. In children the bottom portion of the abdominal...