The four abdominal quadrants are the major regions of the abdomen and include the right and left upper and lower quadrants. Each quadrant contains unique structures that have important functions, according to Study.com.
The left upper quadrant contains the stomach, spleen, and portions of the liver, colon, pancreas and kidneys, explains Boundless. The right upper quadrant contains the liver, gallbladder, duodenum, and some of the pancreas and colon. The left lower quadrant contains the bottom portion of the colon and portions of the reproductive system. The right lower quadrant contains the appendix, the upper part of the colon, and portions of the reproductive system.