four Quadrants are formed by vertical line through median plane and horizontal line (transumbilical plane at the L4 level) through the umbilicus.
Nine regions of the abdomen are formed by two horizontal and two vertical lines. Left and right vertical lines are passing through the mid clavicular line. Upper horizontal line (subcostal plane) is passing through the lowest edge of the thoracic cage, mostly 10th costal cartilage. The lower horizontal line is the intertubercular line connecting the iliac tubercles of the iliac crest of the pelvis.
right hypochondrium – epigastrium – left hypochondrium
right lumbar – umbilical – left lumbar
right inguinal – hypogastrium – left inguinal