Abdominal surface anatomy

Abdominal surface anatomy can be described when viewed from in front of the abdomen in 2 ways:

1. divided into 9 regions by two vertical and two horizontal imaginary planes
2. divided into 4 quadrants by single vertical and horizontal imaginary planes

These regions and quadrants are of clinical importance when examining and describing pathologies related to the abdomen

Nine abdominal regions

Horizontal planes

The dividing planes are based on lines drawn between easily palpable bony points. The horizontal planes are also of importance as they provide useful landmarks on cross-sectional imaging. The two horizontal lines are:

• subcostal plane
  • corresponds to a line drawn joining the lower most 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 (clockwise from the top):

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

Four abdominal quadrants

Horizontal plane

The dividing plane is a horizontal line drawn through the umbilicus.

Vertical plane

The vertical line is down the midline of the body, overlying the linea alba from the xiphoid to the pubic symphysis.

Surface anatomy

The above lines intersect and divide the abdomen into four quadrants (clockwise from the top):

• right upper quadrant fossa (RUQ)
• right lower quadrant fossa (RLQ)
• left lower quadrant fossa (LLQ)
• left upper quadrant fossa (LUQ)