Video: Regions of the abdomen

Today, we'll have some fun exploring the regions of the abdomen.

In today's tutorial, we're going to identify two methods of dividing the abdomen into smaller regions – the four-quadrant scheme and the nine region scheme. We will then briefly explore the contents of each of the nine regions and finish off this video with a clinical note on the regions of the abdomen.

Before we dive into the bulk of this tutorial, let's just take a moment to familiarize ourselves with the location of the abdomen.

The abdomen is the region of the body found between the thorax and the pelvis. Many organs and structures are located within the abdominal cavity. I'm sure you know where some of these organs lie, but it would be helpful to have a method to accurately localize each structure.

Clinicians and anatomists divide the abdomen into smaller regions in order to effectively communicate the location of structures and to identify the location of any injuries and pathologies that may occur in each area.

The quadrant scheme divides the abdomen into four separate quadrants, as we can see here in this image. This is done by drawing a vertical line along the midline of the body forming the so-called anterior median line and a horizontal line at the level of the umbilicus – a line that defines the transumbilical plane. It creates a right and left upper quadrant and a right and left lower quadrant.

The second and more common method to divide the abdomen is by the nine region scheme which uses two vertical lines and two horizontal planes. The paired vertical lines are the left and right midclavicular lines. These lines pass in an inferior direction from the middle of the clavicle to the middle of the inguinal ligament. The first horizontal plane is the subcostal plane. It runs at the level of the lower edge of the 10th costal cartilage. The second horizontal plane is known as the intertubercular plane which passes through the tubercles of the iliac crest and the body of the 5th lumbar vertebra.

These lines and planes divide the abdomen into nine separate regions which include the left and right hypochondriac regions, the epigastric region, the umbilical region, the right and left lateral regions, the right and left inguinal regions, and the hypogastric region. Let's explore these nine regions now.

The first region that we'll look at is the hypochondriac region. Hypochondriac originates from the Greek words hypo meaning underneath and chondrion which means cartilage, indicating that this region lies below the costal cartilages of the ribs. We might also recognize this word as having another meaning as it is used to describe someone who is convinced that they are ill when they are not. That's because years ago when doctors couldn't pin down the cause for ailments within this region, they would use the general anatomical term hypochondria as a diagnosis. This word started being used regularly to mean a general illness that doctors didn't believe existed, thus, forming the definition of the word we use today.

But back to the anatomical region. The hypochondriac region can be divided into left and right regions and sits just above the subcostal plane. Let's begin with the left hypochondriac region. Structures that lie within this region include the tail of the pancreas, the spleen, the left lobe of the liver, the left kidney, parts of the small intestine, parts of the transverse colon, and descending colon, and finally, parts of the stomach. The right hypochondriac region lies on the right side of the upper abdomen above the subcostal plane. Structures that lie within this region include the right lobe of the liver, the gallbladder, the right colic flexure of the large intestine, part of the duodenum, and the upper half of the right kidney.

In between both hypochondriac regions is the epigastric region or epigastrium. As its name suggests, this is the region which lies directly superficial to or over the stomach. From the ancient Greek, epi means upon or above while gastrium relates to the stomach. Therefore, this region obviously contains the stomach – the pyloric part of the stomach to be exact – along with other structures which include the abdominal part of the esophagus.

Lifting the stomach back, we find the spleen, the pancreas, the right and left suprarenal glands and kidneys, the liver which was also removed from this image, parts of the duodenum, and the ureters. The transverse colon which hangs between the right and left colic flexures may also be identified within this region. The transverse colon hangs suspended by the mobile transverse mesocolon and therefore its location can differ slightly from person to person. It is, however, usually located between the epigastric and umbilical regions of the abdomen.

Just below the epigastric region is the umbilical region. This region sits just below the subcostal plane and surrounds the umbilicus or the bellybutton as it is commonly known. Structures within this region include part of the stomach which has been removed from this image, the pancreas, the lower part of the duodenum; the cisterna chyli, a structure from the lymphatic system which is located approximately here; the transverse colon of the large intestine may also be located here, parts of the left and right kidneys, the ureters, and finally, parts of the jejunum and the ileum of the small intestine.

On either side of the umbilical region are the left and right lateral regions, also known as the lumbar regions. Let's begin with the left lateral region of the abdomen. Its name gives us a good idea of where it is situated. Structures such as the lower part of the left kidney, the descending colon, and part of the jejunum and ileum can be found within this region. The right lateral region of the abdomen lies on the other side of the umbilical region. Structures such as the gallbladder, the ascending colon, the lower part of the right kidney, parts of the duodenum, and part of the right lobe of the liver can be found here.

Moving inferiorly, we meet the inguinal region which is named after the inguinal canal and ligament. It lies just inferior to the intertubercular plane and can be divided into the left and right inguinal regions. First, let's take a look at the left inguinal region. Structures of this region include components of the small intestine, the descending colon, and the sigmoid colon. In females, the left ovary and left fallopian tube are also located here. These structures are not visible in this image as they are located deep in the pelvis.

The right inguinal region is situated superior to the right inguinal canal and ligament. Some other structures of this region include the cecum, the appendix, the ascending colon, part of the small intestine. and the right ovary and right fallopian tube in the female pelvis.

Between both inguinal regions is the hypogastric region, also known as the pubic region. This is the final region of the nine-region scheme. Hypogastric essentially means below the stomach so no components of the stomach will be found within this region. Structures of this region include the ileum, the ureters, the urinary bladder, the sigmoid colon, and the rectum.

So now that we've explored the different regions of the abdomen and their contents, let's take a moment to look at a clinical note on this subject.

Cullen’s sign, named after Thomas Cullen, who first described this pathology, is a hemorrhagic or bruised discoloration located within the umbilicus region of the abdomen. Cullen’s sign may indicate an intraperitoneal hemorrhage or bleed. Similarly, Grey-Turner's sign presents as a bruised discoloration to the lateral regions of the abdomen which is indicative of a retroperitoneal hemorrhage.

Intraperitoneal and retroperitoneal hemorrhaging may be due to a number of factors which may include abdominal trauma, a rupture of the main artery of the abdomen which is the abdominal aorta, intra-abdominal cancer, ruptured ectopic pregnancy, perineal hemorrhage, and acute pancreatitis, amongst others.

Developing a good understanding of the regions of the abdomen is not only important when visually inspecting the abdomen, but also key in investigating abdominal pain. Pain radiating from specific regions of the abdomen can be a tell-tale sign of specific pathologies. For example, pain localized to the right inguinal region may be indicative of appendicitis while pain located in the right hypochondriac region may be suggestive of cholecystitis which is an inflammation of the gallbladder.

In order to identify the root of these suspected pathologies, further investigation is necessary. Knowing the regions of the abdomen is therefore vitally important during physical examinations and in communicating the location of pathologies that may arise.

Before we finish, let's just go through a quick summary of what we learned today.

We began today's tutorial by describing the two different methods used to divide the abdomen. The first method is the four-quadrant scheme. This method divides the abdomen into four regions – the right upper quadrant, the right lower quadrant, the left upper quadrant, and the left lower quadrant.

A more common method of dividing the abdomen is by the nine region scheme. The nine region scheme divides the abdomen into nine separate regions. The first regions that we met were the left and right hypochondriac regions which contained portions of the liver, small intestines, and kidneys. Between the two hypochondriac regions is the epigastric region which contains component of the stomach, the esophagus, and small intestine.

Just inferior to the epigastric region is the umbilical region which surrounds the umbilicus. Contents of this region include parts of the stomach, intestines, and pancreas. On either side of the epigastric region is the right and left lateral region of the abdomen which contains components of the large and small intestines.

Distal to the lateral regions, we found the left and right inguinal region. Structures within these regions include parts of the small intestine, large intestine, and the ovaries and fallopian tubes in females. Between the left and right inguinal region is the final region of the nine region scheme – the hypogastric region. This region contains parts of the small intestine, sigmoid colon, rectum, and urinary bladder.

Finally, we took a look at the Cullen’s and Grey-Turner's signs which indicate a peritoneal hemorrhage from trauma or intra-abdominal pathology and discussed the clinical utility of dividing the abdomen into regions.

That brings us to the end of this tutorial.