In laparoscopic surgery, visual, tactile, and motor skills are limited compared to open surgery or laparotomy. The basic techniques of digestive surgery include dissecting and cutting. To overcome these limits to dissecting or cutting away, the selection of the body posture and the position of the port are important in laparoscopy. The use of a 30° view angle laparoscopy or laparoscopy with a flexible tip enables a multidirectional observation of the surgical field as in laparotomy. With a close view of the operative field, dissection and disconnection also become more precise procedures. Conversely, the close operative field narrows the operative view, and reduces dissections to one small stroke, inevitably increasing the time required for an operation. For these reasons, dissection of the adhesion can be performed using an electrosurgical knife, but an ultrasonically activated device (USAD) is required for dissection with haemostasis.

The basic structure of the peritoneal configuration and body walls in foetal life is shown in Fig. 1.2. A basic understanding of the fascial composition of the body circumference and its interpretations has been provided by Tobin et al. [9] and Sato [10]. According to these interpretations, the structure of the body below the diaphragm can be simplified as a straight intestine within a cylindrical body. Basically, the body composition can then be divided into the composition of the peritoneal cavity (consisting of the cylinder) and the composition of the body wall (consisting of the cylinder wall). In the former, the cranial abdomen includes the dorsal and ventral mesentery, and the caudal abdomen includes only the dorsal mesentery involving the intestine. The latter has a ringed composition, and the body walls are symmetrical in relation to the central position of the muscle layer (Fig. 1.2). The trunk has typically been regarded as an onion-like multi-layered structure [11].

The fascial structure present in the body wall is embryologically represented by the term superficial or deep, defined in relation to the superficial skin surface. The terms anterior and posterior are not used because of their arbitrariness. Analogously to the subcutaneous superficial fascia and subcutaneous deep fascia, the deep subperitoneal fascia and superficial subperitoneal fascia exist circumferentially around the abdominal wall (Fig. 1.2). It is important that the superficial subperitoneal fascia and the deep subperitoneal fascia are independent of each other (Fig. 1.2c) and the two fasciae sandwich the aorta from ventral and dorsal sides directly toward the pelvic space.

Unless the continuity of the two subperitoneal fasciae to the pelvic space is guaranteed, this basic configuration (Fig. 1.2) also becomes imperfect. Therefore, to examine the fascial composition in the pelvic space, the terms deep subperitoneal fascia and superficial subperitoneal fascia will be used herein to refer to the pelvic space in consideration of its continuity from the peritoneal cavity. Unless the continuity of the two subperitoneal fasciae is guaranteed, the textbook of surgical procedures also becomes imperfect.

With regards to the relationship between intestinal rotation and each mesentery, the dorsal mesentery (Fig. 1.2) rotates around the superior mesenteric artery (SMA) (Fig. 1.3) [13]. The concept of fusion fascia is thus indispensable when considering the relationship between the peritoneum and the mesentery at the terminal end of rotation of the intestine. After fusion of the bilateral mesentery with the peritoneum, the fixation of the colon to the retroperitoneum is complete.

When we dissect the plane between the fusion fascia of the colon and the deep subperitoneal fascia, it is often possible to see another fascia, for example in the ascending colon or in sigmoid colon surgery. The mesentery of the colon may not necessarily be constituted by two layers. The peritoneum is the widest among the serosa of the body and is divided into the parietal peritoneum and visceral peritoneum. The parietal peritoneum covers the abdominal cavity, the pelvic cavity, and the diaphragm surface. The visceral peritoneum covers the internal organs of the abdomen and pelvis, and is generally considered to also include the mesentery. Originally, the peritoneum completely covers the entire intestinal tract. The mesentery, including the parietal peritoneum, is made of a fibrous layer (the tunica subserosa) and a surface layer of mesothelium (tunica serosa) [14]. The deep subperitoneal fascia is extended to the colon wall through the dorsal mesentery (Fig. 1.4) [10]. Thus, it may be natural that the mesentery is composed of four fasciae. These features are important in the clinical anatomy of the dissection at the hepatic flexure of the right hemicolectomy and for the dissection of the dorsal side at the Denonvilliers’ fascia. The fascia seen on dissection should not be unconditionally believed to be artifacts resulting from surgical interventions. However, what is important is not the number of fasciae, but that the fasciae are used to indicate the correct plane to be dissected.

It is not possible to ignore the relationship between the stomach and the colon in order to understand the overall image of the colon. With regards to the description of this area, there are many errors in many existing books. To understand the boundaries for dissecting and cutting, you must understand whether the fascia belongs to the stomach or to the transverse colon in every stomach or pancreatic operation.

By applying the intestinal rotation and fusion fascia to this part, it is possible to understand its fascial composition. In other words, what is referred to as the gastro-colic ligament is the ligament stretching between the stomach and the transverse colon, which is none other than the omentum. Originally, two sheets of dorsal mesentery became four sheets and then formed the omentum that extends between the stomach and transverse colon. The third sheet of the dorsal mesentery is the posterior wall of the omental bursa, and the fourth sheet of the dorsal mesentery fused with the ventral side of the transverse mesocolon in foetal life (Fig. 1.5). The omentum is tissue belonging to the stomach, which was formed by the original dorsal mesentery (also known as the posterior gastric mesentery) that is stretched caudally. The transverse mesocolon is composed of a ventral and dorsal leaf (generally an anterior and a posterior leaf); it has no relationship at all with the stomach. The root of the transverse colon lies in the caudal edge of the pancreatic body and tail and the transverse mesocolon extends from there as a characteristic fan-shaped mesentery (Fig. 1.3). In the final process of bowel rotation, the fourth sheet of the dorsal mesentery (omentum) and the ventral leaf of the transverse mesocolon are fused (Fig. 1.5). To better understand these relationships, it helps to consider the connections between the omentum and the transverse mesocolon as if they are divided into two stages during the course of intestinal rotation. In the sagittal sectional view at the centre of the transverse colon, the omentum and mesocolon are irrelevant (Fig. 1.5a), however, the fusion fascia is formed (Fig. 1.5c).