Umbilicus

The umbilicus, commonly called the navel, is a prominent midline landmark of the anterior abdominal wall. It represents the scar remaining after separation of the umbilical cord following birth.

In surface anatomy, the umbilicus is important because it provides a readily identifiable reference point for dividing the abdomen, locating other surface landmarks, describing dermatomal innervation, and understanding several embryological and vascular relationships.

Its exact position is variable. In adults it commonly lies near the L3-L4 vertebral level, but its relationship to the vertebral column can change with age, body habitus, pregnancy, obesity, abdominal distension, and posture.

Location

The umbilicus lies in the midline of the anterior abdominal wall within the linea alba.

It is situated between the xiphoid process superiorly and the pubic symphysis inferiorly, although it is not necessarily positioned exactly halfway between these landmarks.

Vertebral Level

The vertebral level of the umbilicus is variable and should not be treated as a fixed skeletal landmark.

In many adults, its surface position corresponds approximately to the L3-L4 region.

Umbilical Region

In the nine-region division of the abdomen, the umbilicus lies within the central umbilical region.

This region is bounded superiorly and inferiorly by horizontal planes and laterally by the vertical planes used to construct the nine-region system.

Four-Quadrant System

The umbilicus is commonly used as the central reference point for dividing the abdomen into four clinical quadrants.

A vertical median plane and a horizontal transumbilical plane intersect near the umbilicus to create the right upper, left upper, right lower, and left lower quadrants.

Abdominal Quadrants

Quadrant	Position Relative to Umbilicus
Right upper quadrant	Superior and right
Left upper quadrant	Superior and left
Right lower quadrant	Inferior and right
Left lower quadrant	Inferior and left

Transumbilical Plane

The transumbilical plane is a horizontal surface plane passing through the umbilicus.

Because the position of the umbilicus varies, the precise vertebral level of this plane also varies between individuals.

Median Plane

The vertical median plane passes through the center of the body and normally intersects the umbilicus.

Together with the transumbilical plane, it forms the commonly used four-quadrant division of the abdomen.

Linea Alba

The umbilicus is located within the linea alba, the fibrous midline raphe extending from the xiphoid process to the pubic symphysis.

The linea alba is formed by the interlacing aponeurotic fibers of the flat muscles of the anterolateral abdominal wall.

Structure of the Umbilicus

The adult umbilicus is a fibrous scar rather than a functioning opening.

Its appearance reflects healing of the abdominal wall after the umbilical cord separates during the neonatal period.

Umbilical Ring

During fetal life, structures of the umbilical cord pass through the umbilical ring in the developing anterior abdominal wall.

After birth, this opening normally closes and becomes incorporated into the fibrous umbilical scar.

Embryological Importance

The umbilicus marks the former connection between the fetus and placenta through the umbilical cord.

Several adult fibrous structures associated with the internal surface of the anterior abdominal wall represent remnants of fetal vessels and ducts that were related to the umbilical region.

Umbilical Cord

The fetal umbilical cord contains the major vessels connecting fetal and placental circulations.

Normally, it contains two umbilical arteries and one umbilical vein embedded within connective tissue.

Umbilical Vein Remnant

After birth, the left umbilical vein becomes obliterated and forms the round ligament of the liver (ligamentum teres hepatis).

This fibrous remnant runs from the umbilical region toward the inferior surface of the liver within the free margin of the falciform ligament.

Umbilical Artery Remnants

The distal portions of the fetal umbilical arteries become obliterated after birth and form the medial umbilical ligaments.

The proximal portions remain patent and contribute to the superior vesical arteries.

Urachus

The urachus is an embryological connection between the developing urinary bladder and umbilical region.

After birth it normally becomes the median umbilical ligament, which extends from the apex of the urinary bladder toward the umbilicus.

Internal Umbilical Folds

On the internal surface of the anterior abdominal wall, several peritoneal folds converge toward the umbilical region.

Fold	Underlying Structure
Median umbilical fold	Median umbilical ligament, remnant of urachus
Medial umbilical folds	Obliterated distal umbilical arteries
Lateral umbilical folds	Inferior epigastric vessels

Dermatome

The skin around the umbilicus is classically associated with the T10 dermatome.

This relationship makes the umbilicus a useful surface landmark when assessing segmental sensory function of the trunk.

T10 Dermatome

A dermatome is an area of skin supplied predominantly by sensory fibers from a single spinal nerve root.

The T10 dermatome passes approximately through the umbilical region, although dermatomes overlap and their exact boundaries vary between individuals.

Cutaneous Innervation

The anterior abdominal wall is supplied segmentally by thoracoabdominal nerves and the subcostal nerve.

Cutaneous branches emerge through the abdominal wall to supply the skin, with the T10 segment classically corresponding to the umbilical level.

Relationship to Visceral Pain

The umbilical region is clinically important in the localization of certain forms of referred visceral pain.

Visceral afferent fibers from midgut-derived structures commonly enter spinal cord levels around T10, so early pain from some midgut disorders may be perceived near the umbilicus.

Appendicitis and Periumbilical Pain

Early appendicitis may produce poorly localized pain in the periumbilical region because the appendix is a midgut-derived structure and its visceral afferent pathways are associated with approximately the T10 spinal level.

As inflammation reaches the adjacent parietal peritoneum, pain may become more sharply localized to the right lower quadrant.

Periumbilical Region

The term periumbilical refers to the area surrounding the umbilicus.

Symptoms described as periumbilical may arise from the abdominal wall, skin, gastrointestinal tract, vascular structures, or referred visceral pathways.

Vascular Anatomy

The umbilical region lies near an important interface between superficial veins of the upper and lower anterior abdominal wall.

Superficial venous channels around the umbilicus can also communicate with paraumbilical veins associated with the portal venous system.

Paraumbilical Veins

Paraumbilical veins accompany the ligamentum teres region and provide communications between veins of the anterior abdominal wall and the portal venous system.

These connections become clinically important when portal venous pressure is elevated.

Portosystemic Communication

The umbilical region is one site where portal and systemic venous channels can communicate.

Dilation of these collateral veins may become visible on the anterior abdominal wall in significant portal hypertension.

Caput Medusae

Caput medusae describes prominent, dilated superficial veins radiating from the umbilical region.

It is classically associated with collateral venous flow in portal hypertension, although visible abdominal wall veins can have other causes and require clinical interpretation.

Arterial Supply

The skin and abdominal wall around the umbilicus receive arterial blood from anastomosing branches of the superior and inferior epigastric systems and superficial vessels of the abdominal wall.

This vascular network contributes to the rich blood supply of the central anterior abdominal wall.

Lymphatic Drainage

The umbilicus is an important approximate dividing landmark for superficial lymphatic drainage of the anterior abdominal wall.

Superficial lymphatics above the umbilical level generally drain toward axillary lymph nodes, while those below generally drain toward superficial inguinal lymph nodes.

Superficial Lymphatic Watershed

Area	Predominant Superficial Lymphatic Drainage
Above umbilicus	Axillary lymph nodes
Below umbilicus	Superficial inguinal lymph nodes

Clinical Examination

The umbilicus is inspected during routine abdominal examination.

Its position, contour, skin, protrusion, retraction, surrounding veins, inflammation, masses, and discharge can provide clinically useful information.

Normal Variation

The external shape of the umbilicus varies considerably among individuals.

It may be recessed, relatively flat, or protruding without necessarily indicating disease.

Displacement of the Umbilicus

Abdominal distension, masses, pregnancy, obesity, ascites, or previous surgery can alter the position or contour of the umbilicus.

Consequently, it should not be treated as a fixed skeletal reference point.

Pregnancy

As the uterus enlarges during pregnancy, the anterior abdominal wall stretches and the umbilicus may become flattened or everted.

Its position relative to underlying abdominal organs also changes as the abdominal contents are displaced.

Obesity

Increased abdominal adipose tissue can alter the apparent position and depth of the umbilicus.

This contributes to variation in the relationship between the external umbilicus and deeper vertebral or visceral structures.

Ascites

Marked accumulation of fluid within the peritoneal cavity can distend the abdominal wall and alter the appearance of the umbilicus.

An umbilical hernia may become more prominent when intra-abdominal pressure is chronically increased.

Clinical Significance

Umbilical Hernia

An umbilical hernia occurs when abdominal contents protrude through a weakness or defect at the umbilical ring.

Umbilical hernias may occur in infants or adults, although their anatomical basis and associated factors differ.

Infantile Umbilical Hernia

In infants, incomplete closure of the umbilical ring can permit protrusion of abdominal contents.

Many small childhood umbilical hernias close spontaneously as the abdominal wall develops.

Adult Umbilical Hernia

In adults, umbilical or paraumbilical hernias may be associated with increased intra-abdominal pressure, obesity, pregnancy, ascites, or weakening of the abdominal wall.

Paraumbilical Hernia

A paraumbilical hernia occurs adjacent to the umbilicus rather than directly through the original umbilical ring.

It is commonly considered separately from congenital umbilical hernias of infancy.

Urachal Abnormalities

Failure of normal urachal obliteration can produce anomalies such as a patent urachus, urachal cyst, urachal sinus, or vesicourachal diverticulum.

A completely patent urachus can create abnormal communication between the urinary bladder and umbilicus.

Omphalitis

Omphalitis is inflammation or infection involving the umbilical region, particularly important in neonates.

The neonatal umbilical stump can provide a route for infection before complete healing occurs.

Sister Mary Joseph Nodule

A Sister Mary Joseph nodule is a metastatic tumor deposit involving the umbilicus.

It may be associated with intra-abdominal or pelvic malignancy and illustrates the anatomical connections of the umbilical region through lymphatic, vascular, and embryological pathways.

Umbilical Discharge

Discharge from the umbilicus can result from infection, persistent embryological remnants, sinus formation, or other local pathology.

The nature of the discharge and associated findings can provide clues to the underlying anatomical abnormality.

Laparoscopic Landmark

The umbilicus is commonly used as an access region in laparoscopic surgery because it is a recognizable midline landmark and contains a naturally thin scarred portion of the abdominal wall.

Actual port placement depends on the procedure, patient anatomy, previous surgery, and surgical technique.

Umbilicus Compared with Other Abdominal Landmarks

Landmark	Surface Anatomical Importance
Umbilicus	Central abdominal landmark, T10 dermatome, quadrant division
Xiphoid process	Superior midline abdominal reference
ASIS	Pelvic and lower abdominal surface landmark
Pubic symphysis	Inferior midline abdominal reference
McBurney’s point	Right lower quadrant landmark related to appendix

Key Surface Anatomy Features

Feature	Key Point
Structure	Midline scar from former umbilical cord attachment
Location	Anterior abdominal wall within linea alba
Approximate vertebral level	Commonly near L3-L4, variable
Dermatome	T10
Four-quadrant role	Reference for transumbilical and median planes
Embryological venous remnant	Ligamentum teres hepatis
Embryological arterial remnants	Medial umbilical ligaments
Urachal remnant	Median umbilical ligament
Superficial lymphatic landmark	Approximate division between axillary and superficial inguinal drainage
Clinical associations	Umbilical hernia, embryological remnants, portal collateral veins

Anatomical Importance

The umbilicus is much more than an external scar. It is a central landmark that links surface anatomy, embryology, neuroanatomical segmental innervation, vascular anatomy, lymphatic drainage, and abdominal examination.

Its association with the T10 dermatome makes it useful in neurological examination and helps explain the periumbilical distribution of early visceral pain from some midgut structures. Internally, several fetal remnants converge toward the umbilical region, including structures derived from the umbilical vessels and urachus.

The umbilicus also provides a convenient reference for dividing the abdomen into quadrants and is commonly used for surgical orientation. Because its position changes with body habitus and abdominal distension, however, it should be regarded as a practical surface landmark rather than a fixed indicator of a single vertebral level.