Human Anatomy
Surface Marking of the Abdomen
Abdominal surface marking for MBBS: transpyloric and subcostal planes, McBurney's point, inguinal rings and organ projections, mapped to NMC codes AN55.1 and AN55.2.
MedNext Academy | 3 min read
Surface Marking of the Abdomen
Abdominal surface marking for MBBS: transpyloric and subcostal planes, McBurney's point, inguinal rings and organ projections, mapped to NMC codes AN55.1 and AN55.2.
This chapter teaches how to translate deep abdominal structures onto the body surface using standard planes and bony landmarks. It underpins clinical examination, the siting of incisions and the interpretation of pain referred to specific regions.
High-yield: Surface Marking of the Abdomen
- The transpyloric plane of Addison lies halfway between the jugular notch and the pubic symphysis, at the level of the first lumbar vertebra.
- The transpyloric plane crosses the pylorus, the neck of the pancreas, the origin of the superior mesenteric artery and the hila of the kidneys.
- McBurney's point lies at the junction of the outer third and inner two-thirds of a line from the umbilicus to the right anterior superior iliac spine, and marks the base of the appendix.
- The subcostal plane passes through the lower border of the tenth costal cartilage at the level of the third lumbar vertebra.
- The transtubercular plane joins the tubercles of the iliac crests at the level of the fifth lumbar vertebra.
- The nine regions of the abdomen are mapped by two vertical midclavicular lines and the subcostal and transtubercular horizontal planes.
- The superficial inguinal ring is a triangular gap in the external oblique aponeurosis, just above and lateral to the pubic tubercle.
- The deep inguinal ring lies about one finger-breadth above the midpoint of the inguinal ligament, lateral to the inferior epigastric vessels.
- The fundus of the gall bladder projects at the tip of the right ninth costal cartilage, where the lateral border of the right rectus abdominis meets the costal margin.
- The spleen underlies the left ninth to eleventh ribs along their long axes, and is not palpable until it enlarges to about three times its size.
- The lower border of the liver in the midclavicular line lies at the right costal margin in the healthy adult.
- The hila of the kidneys lie at the transpyloric plane, with the right kidney a little lower than the left because of the liver.
- The ileocaecal junction lies deep to the intertubercular plane in the right iliac region.
- The aortic bifurcation into the common iliac arteries occurs at the level of the fourth lumbar vertebra, just below and left of the umbilicus.
- The surface projection of the pancreas runs along the transpyloric plane, with the head cradled in the duodenal loop to the right of the midline.
Key abdominal planes and their vertebral levels
- **Transpyloric plane:** L1 level. Pylorus, neck of pancreas, origin of the superior mesenteric artery, renal hila and the ninth costal cartilage tips.
- **Subcostal plane:** L3 level, through the lowest point of the tenth costal cartilages.
- **Transtubercular plane:** L5 level, joining the iliac tubercles; marks the intertubercular line of the nine-region grid.
- **McBurney's point:** Outer third of the umbilicus to right anterior superior iliac spine line; base of the appendix.
NMC competencies in this chapter
- **AN55.1:** Surface marking of abdominal regions and planes, superficial and deep inguinal rings, McBurney's point and renal landmarks
- **AN55.2:** Surface projection of the stomach, liver, gall bladder fundus, spleen, duodenum, pancreas, ileocaecal junction and kidneys
Frequently Asked Questions
What is the transpyloric plane and why does it matter?
It is a horizontal plane at the first lumbar vertebra, halfway between the jugular notch and the pubic symphysis. It crosses the pylorus, the neck of the pancreas, the origin of the superior mesenteric artery and the renal hila, so it locates several deep structures at once.
Where exactly is McBurney's point?
At the junction of the outer third and inner two-thirds of a line drawn from the umbilicus to the right anterior superior iliac spine. It overlies the base of the appendix and is the classic site of maximal tenderness in appendicitis.
How do you locate the fundus of the gall bladder on the surface?
At the tip of the right ninth costal cartilage, where the lateral border of the right rectus abdominis crosses the costal margin. Tenderness here on inspiration is the basis of Murphy's sign.
Why is surface marking useful for exams and the clinic?
It links anatomy to physical examination and imaging. Knowing where organs project lets you interpret guarding, plan incisions and site drains, and the same landmarks recur in radiology and clinical questions.
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