The human abdomen is divided into quadrants and regions by anatomists and physicians for the purposes of study, diagnosis, and treatment.[1][2] The division into four quadrants allows the localisation of pain and tenderness, scars, lumps, and other items of interest, narrowing in on which organs and tissues may be involved. The quadrants are referred to as the left lower quadrant, left upper quadrant, right upper quadrant and right lower quadrant. These terms are not used in comparative anatomy, since most other animals do not stand erect.
The left lower quadrant includes the left iliac fossa and half of the flank. The equivalent in other animals is left posterior quadrant. The left upper quadrant extends from the umbilical plane to the left ribcage. This is the left anterior quadrant in other animals. The right upper quadrant extends from umbilical plane to the right ribcage. The equivalent in other animals is right anterior quadrant. The right lower quadrant extends from the umbilical plane to the right inguinal ligament. This in other animals is the right posterior quadrant.
The nine regions offer more detailed anatomy and are delineated by two vertical and two horizontal lines.
Quadrants
Quadrants of the abdomenDiagram showing which organs (or parts of organs) are in each quadrant of the abdomen
The left lower quadrant (LLQ) of the human abdomen is the area left of the midline and below the umbilicus. The LLQ includes the left iliac fossa and half of the left flank region. The equivalent term for animals is left posterior quadrant.
Important organs here are:
The left upper quadrant (LUQ) extends from the median plane to the left of the patient, and from the umbilical plane to the left ribcage. The equivalent term for animals is left anterior quadrant. Important organs here are:
The right upper quadrant (RUQ) extends from the median plane to the right of the patient, and from the umbilical plane to the right ribcage. The equivalent term for animals is right anterior quadrant. Important organs here are:
The right lower quadrant (RLQ) extends from the median plane to the right of the patient, and from the umbilical plane to the right inguinal ligament. The equivalent term for animals is right posterior quadrant. Important organs here are:
Regions of abdomenRegions shown on left in side-by-side comparison with quadrants.
Nine regions of the abdomen can be marked using two horizontal and two vertical dividing lines. The vertical lines are the mid-clavicular lines taken from the mid-point of each clavicle. The upper horizontal line is the subcostal line taken from the inferior parts of the lowest costal cartilages. The lower horizontal line is the intertubercular line connecting the tubercles of the pelvis.[3][4]
On the sides of the abdomen the other six regions are the left and right hypochondriac regions, on either side of the epigastrium; the left and right lumbar flank regions, on either side of the umbilical region, and the left and right iliac or inguinal regions on either side of the hypogastrium.[3][4]
("Hypo-" means below; "epi-" means above; "chondron" means cartilage (in this case, the cartilage of the rib) and "gaster" means stomach. The reversal of "left" and "right" is intentional, because the anatomical designations reflect the patient's own right and left.)
