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Umbilical hernias are commonly encountered congenital anomalies. Most of the time, they present as a protrusion of the umbilicus in the abdomen that is clearly visible and easily palpable. Because of how common they are, it is important to understand how they develop and what the treatment options are.
An umbilical hernia is medically defined as the protrusion of abdominal contents through a defect in the umbilicus. In children, umbilical hernias are congenital, and occur as a result of incomplete degeneration of the “vitelline duct”. Umbilical hernias are more common in children of Afro-American descent, although they are seen widely in all children. They are also more likely to occur in premature children. Female kids are at higher risk than their male counterparts.
Anatomy of a Hernia
Before we dig into the topic of umbilical hernias per se, let us first of all understand the anatomy of a hernia.
By definition, a hernia is made of 3 essential components: a hernia sac, a neck, a body and a hernia ring.
The hernia sac is the structure within which all the contents of the hernia are stored. The hernia neck is the space between the hernia ring and the hernia body. The hernia ring is the opening of the hernia sac; a patent opening through which the contents of the sac protrude outside. Finally, the body is simply the contents of the sac.
How Does An Umbilical Hernia Develop?
At about week 4 of development, the fetus needs a connection with the extra-embryonic tissue to ensure nutrition and continuous growth. This is particularly necessary because at that stage, the umbilical cord is not yet fully formed and is still developing. Henceforth, the yolk sac, which is – at that stage - the primary source of nutrition for the fetus at earlier stages, narrows and forms a longitudinal tube that connects the embryological midgut to the developing umbilical cord. That tube is called the vitelline duct (or omphalomesenteric duct). The primary function of the vitelline duct is to provide adequate nutrients to the developing embryo until the umbilical cord and the placenta both become functional. When the umbilical cord has completely formed and has become fully functional, the vitelline duct degenerates through a physiological process called apoptosis (programmed cell death). At that stage, the umbilical cord takes over the nutrition purposes and connects the fetus to the maternal uterus via the placenta.
If apoptosis fails to occur, the vitelline duct persists and causes a so-called “vitelline fistula”. If apoptosis occurs only at the proximal end of the vitelline duct (the end attached to the midgut of the embryo), the distal end of the vitelline duct persists and causes weakness of the umbilical ring; resulting in a possible umbilical hernia. However, if the vitelline duct degenerates only at the distal end, the proximal end (attached to the midgut) persists and forms what we call a Meckel’s diverticulum.