Abdominal Regions

The abdomen is divided into regions to help clinicians localize pain, describe organ positions, and document physical exam findings. There are two common systems: the 4-quadrant system (simpler, used in clinical practice) and the 9-region system (more precise, used in anatomy and detailed examination).

The Dividing Planes

Both systems use imaginary planes drawn through the abdomen:

Median (sagittal) plane - a vertical line through the midline (linea alba), from xiphoid to pubic symphysis
Subcostal plane - horizontal line through the lowest point of the costal margin (10th costal cartilages)
Intertubercular (transtubercular) plane - horizontal line connecting the iliac tubercles
Umbilical plane - horizontal line through the umbilicus (used only in the 4-quadrant system)

System 1: The 4 Quadrants

Formed by one vertical and one horizontal line crossing at the umbilicus. Simple and widely used in clinical settings.

Quadrant	Abbreviation	Key Organs
Right Upper Quadrant	RUQ	Liver (right lobe), gallbladder, right kidney, duodenum, hepatic flexure of colon, part of stomach and pancreas
Left Upper Quadrant	LUQ	Stomach, spleen, left kidney, pancreas (tail/body), splenic flexure of colon, liver (left lobe)
Right Lower Quadrant	RLQ	Appendix, cecum, ascending colon, right ovary/tube (in females), right ureter
Left Lower Quadrant	LLQ	Sigmoid colon, descending colon, left ovary/tube (in females), left ureter

System 2: The 9 Regions

Created by two vertical lines (lateral borders of the rectus abdominis muscles, or mid-clavicular lines) and two horizontal planes (subcostal and intertubercular), dividing the abdomen into a 3x3 grid.

Nine abdominal regions on 3D anatomy model

Upper Row

Region	Location	Key Organs
Right Hypochondriac	Upper right, under ribs	Liver (right lobe), gallbladder, right kidney, hepatic flexure of colon
Epigastric	Upper middle	Stomach, liver (left lobe), duodenum, pancreas (head), adrenal glands, aorta
Left Hypochondriac	Upper left, under ribs	Stomach, spleen, left kidney, pancreas (tail), splenic flexure of colon

Middle Row

Region	Location	Key Organs
Right Lumbar (Lateral)	Middle right	Ascending colon, right kidney (lower pole), small intestine
Umbilical	Central, around the navel	Transverse colon, duodenum (lower part), small intestine (jejunum/ileum), aorta, inferior vena cava
Left Lumbar (Lateral)	Middle left	Descending colon, left kidney (lower pole), small intestine

Lower Row

Region	Location	Key Organs
Right Iliac (Inguinal)	Lower right	Appendix, cecum, right ovary/tube (female), right ureter, small intestine
Hypogastric (Pubic)	Lower middle	Bladder, sigmoid colon, uterus (female), small intestine, rectum
Left Iliac (Inguinal)	Lower left	Sigmoid colon, descending colon, left ovary/tube (female), left ureter

Clinical Relevance

Knowing which region corresponds to which organs helps narrow the differential diagnosis when a patient reports abdominal pain:

Epigastric pain - think peptic ulcer, gastritis, pancreatitis, MI (referred)
RUQ pain - think gallstones, cholecystitis, hepatitis, liver abscess
LUQ pain - think splenic rupture, gastric ulcer, pancreatitis
RLQ pain - think appendicitis, ovarian cyst (right), ectopic pregnancy, inguinal hernia
LLQ pain - think diverticulitis, constipation, ovarian pathology (left)
Hypogastric pain - think cystitis, uterine pathology, PID
Periumbilical pain - think early appendicitis, small bowel obstruction, mesenteric ischemia
Lumbar/flank pain - think renal colic (kidney stones), pyelonephritis, musculoskeletal

The 9-region system is favored in anatomy and for precise organ localization, while the 4-quadrant system is more practical for everyday clinical documentation.

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