Umbilicus – Navel: Anatomy and Clinical Relevance

What is the Umbilicus?

The umbilicus, commonly referred to as the navel or belly button, is the small, scar-like depression located at the center of the abdomen. It is the remnant of the umbilical cord, which connected the developing fetus to the placenta during pregnancy. After birth, the cord is clamped and cut, and the remaining stump dries out and falls off within the first few weeks of life, leaving behind the characteristic navel.

Anatomically, the umbilicus is located at the level of the intervertebral disc between the fourth and fifth lumbar vertebrae (L4/L5) and is used as a major topographic reference point in clinical medicine.

Anatomy and Structure

The umbilicus consists mainly of scar tissue and is surrounded by the abdominal muscles and the peritoneum (abdominal lining). During fetal development, several important structures pass through the umbilical cord:

• Two umbilical arteries: carry deoxygenated blood from the fetus to the placenta
• One umbilical vein: transports oxygenated, nutrient-rich blood from the placenta to the fetus
• Omphalomesenteric (vitelline) duct: connects the fetal gut to the yolk sac in early development
• Urachus: connects the bladder to the umbilical cord during development

After birth, these structures close off (obliterate) and leave behind specific ligaments and folds within the abdomen.

Clinical Significance

The umbilicus is clinically important for several reasons in both diagnostics and surgical practice:

Anatomical Landmark

The navel is used to divide the abdominal surface into four quadrants (right upper, left upper, right lower, left lower) or nine regions. This division helps clinicians accurately localize pain, masses, and other clinical findings during physical examination.

Umbilical Hernia

An umbilical hernia occurs when abdominal contents (such as a portion of the intestine or fatty tissue) protrude through a weakness in the abdominal wall near the navel. It is one of the most common types of hernia, affecting both infants and adults. In newborns, many umbilical hernias resolve spontaneously by age 2 to 4. In adults, surgical repair is often required, especially if the hernia causes pain or grows larger.

Omphalitis in Newborns

Omphalitis is a bacterial infection of the umbilical stump in newborns. It can spread rapidly to surrounding tissues and into the bloodstream, making prompt antibiotic treatment essential. Signs include redness, swelling, warmth, and discharge around the navel.

Laparoscopy and Minimally Invasive Surgery

The umbilicus is a common entry point for laparoscopic (keyhole) surgery. In Single Incision Laparoscopic Surgery (SILS), all surgical instruments are inserted through a single incision at the navel, resulting in reduced scarring and faster recovery compared to traditional open surgery.

Dermatological and Oncological Aspects

The umbilicus can be the site of skin conditions such as inflammation, fungal infections, or contact dermatitis. In rare cases, it may harbor metastatic tumor deposits from intra-abdominal cancers, known as Sister Mary Joseph nodules, which can be an important clinical sign of advanced malignancy.

Embryological Development

The umbilical region plays a central role in embryonic development. The umbilical cord serves as the lifeline between the embryo and the placenta, supplying oxygen and nutrients while removing waste products. Developmental abnormalities in this region can lead to congenital conditions such as:

• Omphalocele: abdominal organs protrude into the base of the umbilical cord
• Gastroschisis: a defect in the abdominal wall to the side of the umbilicus through which intestines herniate
• Meckel diverticulum: a remnant of the omphalomesenteric duct that persists as a pouch in the small intestine

References

1. Sadler T.W. - Langman's Medical Embryology. 14th Edition. Wolters Kluwer, 2019.
2. Muysoms F.E. et al. - Classification of primary and incisional abdominal wall hernias. Hernia, 2009; 13(4): 407-414. PubMed PMID: 19495920.
3. Moore K.L., Dalley A.F., Agur A.M.R. - Clinically Oriented Anatomy. 8th Edition. Wolters Kluwer, 2018.