Abdominal quadrants, regions and planes

The abdomen is a part of the body sometimes casually referred to as the belly or torso.

The organs within this area are said to be contained within a space known as the abdominal cavity, which is bounded by the musculo-aponeurotic walls anterolaterally.

Superiorly, the abdominal cavity extends into the thoracic cage to the 4th intercostal space and is separated from the thoracic cavity by the diaphragm.

Some organs found within the upper region of the abdominal cavity, such as the spleen, liver, stomach and parts of the kidneys, are actually protected by your rib cage.

Inferiorly, the lower portion of the abdominal cavity doesn't have a physical boundary because it’s continuous with the pelvic cavity; so sometimes, they’re lumped together under the term “abdominopelvic cavity”.

However, to better understand the anatomy, the inferior boundary, which separates the abdominal cavity from the pelvic cavity is an imaginary plane called the pelvic inlet, which divides the pelvis into a greater, or false pelvis, above, and a lesser, or true pelvis, below.

Similar to how the ribcage protects some of the superior organs of the abdominal cavity, the greater pelvis protects some of the lower organs of the abdomen, including portions of the ileum, cecum, appendix, and sigmoid.

You may have already noticed how many organs there are inside the abdominal cavity. So to make it easier to describe their location, the abdomen is often divided into anatomical quadrants, of which there are four, or regions, of which there are nine.

Let's start with the quadrants. To get those four quadrants, imagine a line running down from the xiphoid process, or tip of the sternum, all the way down to the pubic symphysis. This line is the median plane and divides the abdomen into a left and a right half.

The second imaginary line goes straight through the belly button or umbilicus, from left to right. This line creates the transverse or transumbilical plane and divides the abdomen into an upper and lower half. So the resulting quadrants are the right upper quadrant, left upper quadrant, right lower quadrant, and the left lower quadrant.