The human navel, or umbilicus, is the visible scar left on the abdomen after the umbilical cord detaches following birth. This feature marks the site where the fetus was connected to the placenta, an opening in the abdominal wall that naturally closes. While rare, the possibility of a second umbilical scar does exist and is documented in medical literature.
The Anatomical Rarity of a Second Navel
The medical term for having more than one navel is supernumerary umbilicus, or polyumbilicus, and the condition is extremely rare. A true second umbilicus is a congenital anomaly, representing a complete second scar tissue site. These cases are so uncommon that they are mainly documented as individual case reports in scientific journals. When a second navel forms, it warrants a clinical investigation.
A true polyumbilicus can be associated with other underlying congenital defects. The scar may signify a persistent internal connection to remnants of fetal structures, such as the urachus or the omphalomesenteric duct. These internal structures normally close and regress completely, but can sometimes remain partially open, potentially leading to issues involving the gastrointestinal or urinary tracts.
Embryological Origins of Duplication
The formation of the navel results from a complex process during early fetal development involving the closure of the abdominal wall. Around the fourth week of gestation, the embryonic folding process pulls the lateral walls of the abdomen together at the midline. This fusion encircles the vitelline duct, the urachus, and the umbilical blood vessels, creating the single umbilical cord insertion point.
A second navel develops when there is an incomplete or abnormal fusion of the abdominal midline structures during this folding. This error can result in two distinct, separate areas where the umbilical structures were attached, or a split remnant of the cord’s base. The duplication occurs when the developmental closing mechanism establishes two separate points of entry and exit for the umbilical cord structures. The resulting second scar may be smaller and less defined than the primary navel.
Identifying Pseudonavels and Mimics
Many features mistaken for a second belly button are actually benign skin anomalies known as pseudonavels. The most frequent mimic is an accessory nipple, medically termed polythelia, which can appear anywhere along the embryonic “milk line” that extends from the armpit to the groin. These accessory nipples can resemble a small mole, a pigmented spot, or a dimple.
Other common pseudonavels are scars resulting from previous medical procedures, particularly laparoscopic surgeries or feeding tube placements. These surgical incisions are often made in the abdominal area and can heal into round, depressed scars that closely mimic the shape of an umbilicus. The fundamental difference is that a true umbilicus is a scar derived from the detachment of the umbilical cord vessels, while a pseudonavel is merely a surface depression, pigmented mark, or scar tissue.