The area defined as lateral on the abdominal surface cannot be accurately delimited. The costal and iliac bone limits and the lateral edge of the rectus abdominis muscle are the only recognizable structures. The fibers of the external oblique muscle descend from its posterior costal origin to insert on the external edge of the iliac crest. Therefore, we propose to consider the anterior axillary line as the limit for the separation of the lateral areas (L2–3) from the lumbar zone (L4 or “L”). The proper knowledge of the morphology and function of the abdomen lateral muscles will allow us to perform a more accurate operation, focused on restabilizing their function. The anatomic structures to be considered during this operation are: skin, subcutaneous tissue with the fascia of Camper and the deep fascia of Scarpa, and a triple muscular layer, the oblique, and the transverse abdominal muscles.

Knowledge on aponeurosis and muscular insertions is essential to fix hernias safely, layer by layer. Between the external and internal oblique muscles, there is an avascular area that allows its separation. The internal and transverse oblique muscles cannot be separated easily and between them we can find the neuro-vascular package of lumbar and inferior intercostal branches. On the medial level, both intramuscular areas are very limited because they are part of the rectus sheath. Thus, it is difficult to extend a mesh to the hernia defect medially.

The clinical presentation depends on the size and the location of the hernia. They can appear right after the surgery or two or more years later. Patients report subjective discomforts and often pain that impacts their quality of life. Objectively, a protrusion on the abdominal wall with effort is obvious and that can reach big dimensions. Hernia can become painful indicating tissue suffering, evolving to incarceration or strangulation with mechanical ileus and viscera distress. The risk of complications is usually low but cannot be predicted (Fig. 17.2) [3].

The diagnosis is usually made clinically, but most patients will have already a CT scan when they see a surgeon. Decubitus exploration, without tensing the abdomen flat muscle, helps recognize hernia mass. The elevation of the extended legs increases the intra-abdominal pressure and tenses the rectus and flat muscles, which can hide the hernia. The elevation of the head tenses the rectus muscles but not the flat ones, which allows hernias to be become more visible and easily palpable. If patient does need a CT a scan, we advise to use a dynamic CT to complete the preoperative study and plan surgery. It allows to calculate accurately the size of the hernia and to value the adjacent tissues (Fig. 17.3).

The open technique surgery of the lateral hernia is not standardized due to its variety, higher anatomical complexity, and its low frequency. Anatomical reconstruction techniques are not advisable, except for small cases, and performed by surgeons with high experience. The techniques of fascial imbrication or muscle flaps are complex and must be reserved for experienced groups. In our hands open lateral approach through previous incision and the use of a nonabsorbable synthetic mesh as reinforcement is the best technique of repairing these hernias.