Regions of the abdomen
The regions of the abdomen are theoretical divisions used by clinicians to help localize, identify and diagnose a patients symptoms. There are two main forms of categorization, the first which is simpler and is mapped out by dividing the abdomen into four quadrants, while the second method divides it into nine segments. Either of these two ideas about the abdominal regions are internationally recognized and can be used on a daily basis during clinical practice, it is simply up to the physician on how they wish to present their findings. This article will discuss both schemes and include a list of the internal organs and other important anatomical structures that can be found within each region.
The Four Region Scheme
The four anatomical regions of the abdomen are known as quadrants. They are separated by theoretical anatomical lines that can be traced on the abdomen using certain anatomical landmarks. The median plane is that which follows the linea alba and extends from the xiphoid process to the pubic symphysis and splits the abdomen vertically in half. The transumbilical plane is a horizontal line that runs at the level of the umbilicus. These two planes transect at the umbilicus is a cross-like form and divide the abdomen into four quarters.
The right upper quadrant (RUQ) in a craniocaudal order contains the right lobe of the liver, the gallbladder, the pylorus of the stomach, the entire duodenum, the head of the pancreas, the right kidney and the right suprarenal gland, the distal ascending colon, the hepatic flexure of the colon and the right half of the transverse colon.
The left upper quadrant (LUQ) in a craniocaudal order contains the left lobe of the liver, the spleen, the stomach, the jejunum, the proximal ileum, the body and the tail of the pancreas, the left kidney and the left suprarenal gland, the left half of the transverse colon, the splenic flexure of the colon and the superior part of the descending colon.
The left lower quadrant (LLQ) contains the distal descending colon, the sigmoid colon and the left ureter.
The Nine Region Scheme
Compared to the four region scheme this division of the abdomen may seem more complicated. However, it can help to further localize clinical symptoms and arrive at an accurate diagnosis more quickly. There are two vertical planes and three horizontal planes that are used to separate the nine segments. The vertical planes are known as the left and right midclavicular lines and they run from the midpoint in the clavicle caudally towards the midpoint of the inguinal ligament. The horizontal planes which are mentioned here in a craniocaudal order, include the subcostal plane, the transumbilical plane and the transtubercular plane. The subcostal plane runs horizontally through the lower border of the tenth costal cartilage on either side, while the transumbilical plane has already been mentioned above in the four scheme region. Finally, the transtubercular plane passes through the tubercles of the iliac crest and the body of the fifth lumbar vertebra.
The right and left hypochondriac regions are found superiorly on either side of the abdomen, while the epigastric region sits between them in a central superior position. The right and left lumbar regions surround the umbilical region, which is central and has the umbilicus as its centre point. Lastly, the right and left inguinal regions are found inferiorly on either side of the hypogastric region, which is the most inferior of the central line of segments.
Each of the nine regions shall now be listed individually, running craniocaudally from left to right:
The left hypochondriac region contains the stomach, the top of the left lobe of the liver, the left kidney, the spleen, the tail of the pancreas and parts of the small intestine, the transverse colon and the descending colon.
The left lumbar region contains a portion of the small intestine as well as the descending colon and the tip of the left kidney.
The left inguinal region contains part of the small intestine, the descending colon, the sigmoid colon as well as the left ovary and the left fallopian tube in females.
The epigastric region contains the esophagus, the stomach, the liver, the spleen, the pancreas, the right and left kidneys, the right and left ureters, the right and left suprarenal glands, the small intestine and the transverse colon.
The umbilical region contains the stomach, the pancreas, the small intestine, the transverse colon, the right and left kidneys, the right and left ureters and the cisterna chyli.
The hypogastric region contains the small intestine, the sigmoid colon, the rectum, the urinary bladder and the right and left ureters. In females, the uterus, the right and left ovaries and the fallopian tubes can be found. In males, the vas deferens, the seminal vesicle and the prostate can be found.
The right hypochondriac region contains the liver, the gallbladder, the small intestine, the ascending colon, the transverse colon and the right kidney.
The right lumbar region contains the tip of the liver, the gallbladder, the small intestine, the ascending colon and the right kidney.
The right inguinal region contains the small intestine, the appendix, the cecum and ascending colon and in females the right ovary and right fallopian tube.
Grey-Turner’s sign is a redness or bruising that can be seen on the right lumbar region after a period of 24 to 48 hours and indicates a retroperitoneal hemorrhage. Its presence is significant because it can be predictive of severe hemorrhagic pancreatitis, abdominal injury or even metastatic cancer. Cullen’s sign is a discoloration of the skin around the umbilicus and points to a peritoneal hemorrhage.