Abdominal herniae occur most often in the umbilical and inguinal regions. Sometimes the recti muscles separate and a median protrusion results; or they may occur at the site of a previous operation.

Umbilical herniae are of three kinds, congenital, infantile, and acquired.

Congenital umbilical hernia is due to a developmental defect. In the embryo the umbilicus transmits (1) the vitelline duct, passing from the umbilical vesicle to the small intestines; (2) two umbilical arteries, which inside the abdomen are called hypogastric and pass to the internal iliacs through the superior vesicals; (3) one umbilical vein passing to the liver through the round ligament; (4) the stalk of the allantois, which, on entering the abdomen, is called the urachus, and passes down to the bladder. At birth these structures, with a myxomatous tissue called Wharton's jelly, are covered with amniotic tissues and form the umbilical cord.

If development is interfered with, a cleft is left in the umbilical region into which intestine or other organs may protrude. If only intestine protrudes, it pushes up into the umbilical cord, and constitutes a congenital umbilical hernia. If the intestine is included when the cord is ligated, death from strangulation will ensue; hence the danger of this form of herniae. If the urachus remains patulous it may form a urinary fistula. The hypogastric arteries become obliterated and, opposite Poupart's ligament, have two fossae, one to their outside and one to their inside. Into these fossae direct inguinal herniae may pass. The persistence of the vitelline duct may cause a finger-like projection, called Meckel's diverticulum, on the ileum, about 2 or 3 feet above the ileocaecal valve. Sometimes a band passes from Meckel's diverticulum to the umbilicus and causes strangulation of other coils of the intestine. We have operated on one such case. The umbilical vein becomes obliterated and the small vein found in the round ligament of adults, called by Schiff the parumbilical, is a new formation, and not the original fetal umbilical vein.

Infantile umbilical hernia is the common form which appears soon after birth. It does not contain omentum so constantly as does adult hernia, because it does not hang so low, nor is it so well developed.

Acquired umbilical hernia is the form seen in adults. The presence of the urachus and hypogastric arteries so strengthens the lower edge of the umbilical ring that hernial protrusions make their exit above, hence the hard edge of the ring is nearer the lower end of the hernial sac. - _

These herniae almost always contain omentum, and either transverse colon or small intestine. The contents of the herniae are usually matted together and are adherent. The coverings are very thin, consisting of skin and peritoneum, with a small amount of transversalis fascia and scar-tissue between. Unless extreme care is exercised in operating, the first cut will pass into the sac and wound the intestines or omentum. There are two modes of operating on these herniae. In one operation the sheaths of the two recti muscles are opened and the muscular fibres and sheaths are brought together and sewed in the median line; in the other, two flaps are made from the fibrous walls of the sac and lapped one over the other, thus closing the hernial opening by two fibrous layers. This may be done either longitudinally or transversely.

Fig. 394.   The various forms of congenital inguinal hernia.

Fig. 394. - The various forms of congenital inguinal hernia.