Abdominal surface anatomy

The abdomen, when looking from in front, is divided into nine regions by imaginary planes (two vertical and two horizontal) forming abdominal surface anatomy. The nine regions are of clinical importance when examining and describing pathologies related to the abdomen. The horizontal planes are of further importance as they provide useful landmarks on cross sectional imaging.

Horizontal planes

The dividing planes are based on lines drawn between easily palpable bony points. The two horizontal lines are:

• subcostal plane
  • corresponds to to a line drawn joining the lowermost bony point of the rib cage - usually 10^th costal cartilage
  • body of the L3 vertebra; the origin of the inferior mesenteric artery and 3^rd part of the duodenum lie on this plane
• transtubercular plane
  • corresponds to a line uniting the two tubercles of the iliac crests
  • upper border of the L5 vertebra and the confluence of the common iliac veins (i.e. IVC origin) lie on this plane

Vertical planes

The two vertical planes are similar on each side and follow a line joining the mid clavicular point to the mid inguinal point. It passes just lateral to the tip of the ninth costal cartilage - which is palpable as a distinct step along the costal margin. It roughly corresponds to the lateral border of the rectus abdominis muscle.

Surface anatomy

The above lines intersect and divide the abdomen into nine regions:

• epigastric region (epigastrium)
• left hypochondrium (LHC)
• right hypochondrium (RHC)
• umbilical region
• left lumbar region (left flank)
• right lumbar region (right flank)
• suprapubic (hypogastric) region
• right iliac fossa (RIF)
• left iliac fossa (LIF)