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A bilateral inguinal hernia is a soft tissue injury that occurs along the inguinal crease, the margin on the front of the hip where the leg meets the body, forming a diagonal line. It is known as bilateral because the injury occurs on both sides, although an inguinal hernia that only affects one side, a unilateral inguinal hernia, is also common. This injury occurs when the peritoneum, the membrane lining the abdominal cavity that encapsulates the organs of digestion, penetrates one of several weak points in the abdominal wall. Pushing through the layers of muscle and connective tissue, it creates a prominent bulge against the skin of the inguinal crease. Much more common in men than in women, a bilateral inguinal hernia occurs at the top of the groin near where the scrotum meets the inguinal crease on either side.
Beneath the layers of skin and fat at the site of a bilateral inguinal hernia are multiple additional layers of tissue stretching from the abdomen to the pelvis, such as the aponeuroses. Aponeuroses are flattened layers of tendon that attach the abdominal muscles to the pubis, the bone in the center of the lower pelvis, like elastic sheets stretching downward to connect the muscles to the bone. As any one aponeurosis does not cover the front of the hip completely, there may be gaps between these tissues. For instance, the conjoint tendon, an aponeurosis linking the transversus abdominus muscle to the pubis along either side of the abdomen, is found to either side of the aponeurosis of the rectus abdominus muscle where these aponeuroses meet the inguinal crease. Between them is a small gap through which arteries, veins, and other vessels pass.
Referred to as Hesselbach’s triangle, this gap is a common site of a bilateral inguinal hernia. Also known as the inguinal triangle, it is found just above and to either side of the pubic bone on the front of the hip. It is bordered along its medial or inside margin by the aponeurosis of the rectus abdominus, along its upper outside edge by a pair of blood vessels known as the inferior epigastric artery and vein, and along its lower outside margin by the inguinal ligament, which follows the inguinal crease.
The type of bilateral inguinal hernia that occurs at Hesselbach’s triangle is known as a direct inguinal hernia because the contents of the abdominal cavity push directly through the aponeuroses of the muscles in the wall. This is in contrast to an indirect inguinal hernia, which also may occur bilaterally and in which the tissue pushes not through the abdominal wall but into the inguinal canal, the duct that contains the spermatic cord in men and the round ligament in women. Much more common in men, this condition occurs when the peritoneum penetrates the canal via its upper opening, the deep inguinal ring, and protrudes through the other end of the canal, the superficial inguinal ring. It caused by a failure of the deep inguinal ring to close during embryonic development after the testicles form and drop into the scrotum, leaving the opening exposed to the abdominal wall.