Clinical aspect of anterior abdominal wall incisions

Anatomy of anterior abdominal wall incisions

Surgical incisions are made into the anterior abdominal wall primarily in order to gain access into the peritoneal cavity. Sometimes this situation is reversed to that the incision is made into the posterior abdominal wall in order to reach the retroperitoneal structures. These retroperitoneal structures like the kidneys, suprarenal glands, ascending and descending colon, duodenum and pancreas are best approached from the posterior abdominal wall incisions while intraperitoneal structures such as the intestines (small), sigmoid and transverse colon etc (stomach, liver, spleen) can be reached via the anterior abdominal wall incisions. There are several incisions which can be made into the anterior abdominal wall as follows

a. Gridiron incision- this incision is made into the anterior abdominal wall without cutting through their muscles. It is therefore called the split-muscle incision. This incision, takes into consideration, the path or course of the fibers of the muscles of the anterior abdominal wall. Hence it is noted that the external muscle/ aponeurosis runs downwards and forwards just like the external intercostal muscle. This is followed by the internal oblique muscle and aponeurosis which runs upwards and forwards and then by the transverses abdominis which runs transversely. A good example of the gridiron incision is that made for appendicectomy in order to expose the caecum and the appendix which the caecum carries. In this incision the knife is passed through the so called McBurney’s point, which is a point placed at the junction between the lateral and intermediate 1/3 of the line joining the umbilicus with the anterior superior iliac spine on the right. This incision runs downwards and forwards along the McBurney’s point and passes through the following layers

1. Skin

2. Campers fascia

3. Scarpa’s fascia

The next layer is the layer of external oblique aponeurosis and muscle

The fibers of this layer are split to make room for the incision rather than using a knife.

The next layer is the layer of the internal oblique and again the fibres of this muscle/aponeurosis are split along their course, which means the split runs upwards and forwards.

Finally the split in the fibers of the transversus abdominis runs transversely.

After the layers of the muscles, we then reach the parietal peritoneum. This peritoneum is divided using a knife  longitudinally or transversely in order to expose the peritoneal cavity. The appendix may lie behind the caecum and this is the position preferred in 75% of cases- i.e. it is retrocecal or retroileal.

It also can lie in front of the cecum, Ie pre-ileal or it may be pelvic in position thereby lying in the abdominopelvic corridor or within the greater pelvis. It may be long or short and it may have various types of curvature. The cecum itself may be retroperitoneal which then renders the operation more delicate. But in most cases it is intraperitoneal and it can then be easily delivered through the incision to the outside where operation on its contained appendix takes.

After the procedure, the surgeon does not bother to stitch back the muscular layers. But he stitches the skin, superficial fasciae and parietal peritoneum. It is believed that the muscle fibers will realign once the operation is finished and therefore this method obviates the need for incision, or stitches into the muscles which normally will cause scar formation.

Midline incisions

These are incisions given to the linea alba either superior or inferior, i.e. below or above the umbilicus. They are very simple since they simply pass through the fibrous conglomeration which forms the linea alba. The incision only passes trough skin, superficial fascia, before reaching the linea alba. After the linea alba, the incision is made longitudinally into the parietal peritoneum. Its main advantage is speed. Hence it is favoured in Caesarean section, where speed is required in order to deliver the baby speedily. It has a major disadvantage which is that it heals with ugly scars and takes a long time to heal because of its relative avascularity.

Also the linea alba incisions are very simple to make and even to stitch back.

Paramedian incision

This type of incision passes throough the anterior abdominal wall and its various layers but avoids the midline or the linea laba. Examples include subcostal incision for splenectomy or other operations on the spleen. Another important incision is the transverse incision which is used for cosmetic reasons- called in gynaecology Pfannenstiel incision. This incision is placed in the hypogastrium and is used to access the pelvic organs such as uterus, fallopian tubes, ovaries, and male reproductive organs.

The incision passes through the skin, then superficial fasciae- Campers and Scarpa. Then it reaches the anterior wall of rectus sheath. The recti are then pushed laterally in order to expose the posterior sheath. This sheath is now divided in continuity with the parietal peritoneum and transversalis fascia. Below the arcuate line of Douglas there is no posterior wall of the rectus. The incision into the posterior structures now changes to a longitudinal one in order to adequately expose the peritoneal cavity. After the operation, the layers are closed up one by one until it reaches the skin

Another type of non midline incision is the common hernial incision. This incision is made with its inferior edge running from the external inguinal ring, backwards and upwards.







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