Abdominal regions and quadrants

Why the abdomen is divided

The abdominal cavity is the largest cavity of the body and holds organs of several systems: digestion, urinary excretion and, in the pelvis, reproduction. Unlike the chest, the abdomen has no complete bony cage; its walls are muscular, and the position of organs shifts with breathing, posture, meals and body size. A single named point is therefore less useful than a region. Dividing the abdomen into standard areas gives a stable reference that does not depend on the individual, so a note written in one hospital means the same thing in another. The divisions also help with examination: each area suggests which organs to consider and which way to move the examining hands, and they guide where a stethoscope, ultrasound probe or surgical incision is placed.

For example: The liver sits under the right rib cage and moves several centimetres with breathing, which is why its edge is described relative to the rib margin rather than to a fixed point on the skin.

The four quadrants

The four-quadrant system uses two lines that cross at the umbilicus. One runs vertically along the midline, the median plane; the other runs horizontally through the navel, the transumbilical plane. They create the right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ) and left lower quadrant (LLQ). Remember that right and left are the patient’s sides. The RUQ contains most of the liver, the gallbladder and part of the duodenum; the LUQ contains the stomach, the spleen and part of the pancreas; the RLQ contains the caecum, the appendix and the lower part of the ascending colon; the LLQ contains the lower descending and sigmoid colon. The four-quadrant system is quick and widely used, but because it is coarse, it is paired with the nine-region system when more precision is needed.

For example: Appendicitis classically causes pain in the right lower quadrant, although it often begins as vague pain around the umbilicus before localising.

Common misconception: The quadrants are the patient’s right and left, not the observer’s. Facing the patient, their right upper quadrant is on your left.

The nine regions

For more precise description, the abdomen is divided into nine regions by four lines: two vertical and two horizontal. The vertical lines are the right and left midclavicular lines, drawn downward from the midpoint of each clavicle. The upper horizontal line is the subcostal line, drawn along the lower edge of the rib cage; the lower horizontal line is the intertubercular line, drawn between the two hip prominences (the iliac tubercles). The resulting grid has three rows and three columns. The top row is the right hypochondriac, epigastric and left hypochondriac regions. The middle row is the right lumbar, umbilical and left lumbar regions. The bottom row is the right iliac (inguinal), hypogastric (pubic) and left iliac regions. Each name describes a position, so the epigastric region is above the stomach area and the hypogastric region is below it.

For example: The epigastric region lies in the midline just below the sternum. Pain there commonly prompts questions about the stomach, the lower oesophagus, the pancreas and the liver.

Enlarge illustration ↗

Which organs lie where

Knowing the contents of each area turns the grid into a reasoning tool. The right hypochondriac region contains the liver and gallbladder; the epigastric region contains the stomach, the upper duodenum and part of the pancreas; the left hypochondriac region contains the spleen, the tail of the pancreas and the splenic flexure of the colon. The right lumbar region contains the ascending colon and the right kidney; the umbilical region contains loops of small intestine and parts of the transverse colon; the left lumbar region contains the descending colon and the left kidney. The right iliac region contains the caecum and appendix; the hypogastric region contains the bladder, the lower colon and, in women, the uterus; the left iliac region contains the sigmoid colon. Many organs cross the lines, so the grid narrows the possibilities rather than proving a single diagnosis.

For example: The kidneys lie high and against the posterior wall, so kidney pain is often felt in the lumbar regions and may radiate to the back or groin.

Using the grid in practice

In practice the grid structures the whole assessment. The history records where the pain started, where it is now and where it radiates; the examination moves through the regions so that no area is forgotten; and the note states the finding by region and quadrant so that another clinician can compare later. Imaging requests name the region and the suspected organ, which helps the radiographer choose the right plane and view. Surgical incisions are planned over the region containing the target organ while avoiding important vessels and nerves. The same grid also helps interpret referred pain, in which an organ produces discomfort at a distance: gallbladder pain may be felt at the right shoulder, and diaphragm irritation may be felt at the neck or shoulder tip because of shared nerve supply.

For example: A patient with right iliac fossa pain and tenderness at McBurney’s point raises suspicion of appendicitis, which is then tested with further signs and imaging.