This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
As the intestine descends to form an oblique inguinal hernia it pushes in front of it the following structures: peritoneum, subperitoneal fat, transversalis (infundibuliform) fascia, internal oblique muscle (cremaster), external oblique aponeurosis (intercolumnar fascia), subcutaneous tissue, and skin. These structures are therefore cut in opening the sac to expose the intestine. The hernia always descends in front of the cord and testicle, hence these are posterior. The site of strangulation may be either at the external ring as the hernia passes through the external oblique muscle or at the internal ring as it passes through the transversahs fascia. 1 he deep epigastric artery is always along the inner side of the neck of the sac, therefore division of the stricture must be either upward or up and out, never inward (Fig. 397).
This has been systematized by Bassini of Padua. The neck of the sac having been exposed by incising the aponeurosis of the external oblique, and the cord separated from it, the intestine is to be replaced and the sac ligated as high as possible and cut away. The cord is then raised and the arching fibres of the internal oblique (and transversalis) are sutured beneath it to Poupart's ligament. The cord is to be replaced, and the cut edges of the external oblique are sewed together down to the external ring, leaving sufficient room for the exit of the cord (Fig. 398).
This is so called because it comes directly through the abdominal walls, and not obliquely down through the inguinal canal. It makes its appearance in the neighborhood of the external ring (Figs. 399 and 400).
Fig. 398. - Bassini's operation for the radical cure of oblique inguinal hernia.
Hesselbach's triangle is seen from the interior of the abdomen; it has on its outer side the deep epigastric artery, on its inner side the edge of the rectus muscle, and as its base Poupart's ligament. Direct inguinal hernia pierces the abdominal walls through this triangle. On looking at the abdominal wall from the inside, five folds are seen. In the median line the urachus passes from the umbilicus to the top of the bladder; farther out are the folds formed by the obliterated hypogastric arteries (plica hypogastrica); and still farther out the folds containing the deep epigastric arteries (plica epigastrica). The fossa between the urachus and hypogastric artery is called the internal inguinal fossa (fovea supravesicalis); that between the hypogastric and deep epigastric arteries, the middle inguinal fossa (fovea, inguinalis medialis), and that to the outside of the epigastric artery the external inguinal fossa (fovea inguinalis lateralis). An indirect or oblique inguinal hernia enters the abdominal walls at the external inguinal fossa, to the outer side of the epigastric artery. A direct hernia almost always enters the middle inguinal fossa between the hypogastric and epigastric arteries. The hypogastric fold passes up behind the middle of the external ring close to the outer side of the rectus muscle. On this account a direct hernia rarely enters to the inner side of the hypogastric fold (Fig. 399).