Medical Definition of abdominal region
: any of the nine areas into which the abdomen is divided by four imaginary planes of which two are vertical passing through the middle of the inguinal ligament on each side and two are horizontal passing respectively through the junction of the ninth rib and costal cartilage and through the top of the iliac crest—see epigastric 2b, hypochondriac 2b, hypogastric 1, iliac 2, lumbar 2, umbilical 2
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