UMBILICAL HERNIAS, UMBILICAL ABSCESSES, AND URACHAL FISTULAS - SURGICAL CONSIDERATIONS

The umbilicus is the remnant of the fetal-maternal connection. At birt h, this structure consists of the paired umbilical arteries, a single umbilical vein, and the urachus. Prior to birth, the umbilical vein se rves as the source of oxygenated blood to the fetus via the liver and the ductus venosus/portal vein. The paired umbilical arteries are bran ches of the internal iliac artery and carry waste materials and unoxyg enated blood to the placenta. The urachus is the connection from the f etal bladder to the allantoic sac. Following a normal delivery, the sm ooth muscle that surrounds the umbilicus contracts in response to the stretching of the cord at parturition. Separation of the umbilical cor d allows the umbilical arteries and urachus to retract into the abdome n, where they close by smooth muscle contraction.(11) The umbilical ve in and remnants of the amniotic membrane remain outside the body wall but rapidly collapse in association with smooth muscle contraction; th e umbilicus therefore shrinks and shrivels. The umbilical stalk normal ly dries and thins out by 3 to 4 days post-delivery. The scabbed-over and dessicated umbilical stalk should be totally eliminated by 3 to 4 weeks of age.(18) As the animal matures, the umbilical vein undergoes fibrosis and becomes the round ligament of the liver suspended in the falciform ligament. The umbilical arteries collapse and become the lat eral (round) ligaments of the bladder, and the urachus atrophies, beco ming a vestigial part of the urinary bladder. The body wall. normally closes completely around the umbilical structures within a few days bu t, occasionally, small openings in the linea alba (<1.2 cm) are palpab le for a few months. These most often close spontaneously.