Anatomy - Anastomosis technique, gastrointestinal, with circular stapler

Large and small intestine have a very similar wall structure. The reduced mechanical strength of strictly mucosal sutures stems from the small amount of connective tissue and collagen fibers in the mucosal layer.
Comprising connective tissue with a three-dimensional collagen fiber lattice and elastic meshes, the submucosa constitutes the “load-bearing” part of the intestinal sutures in all parts of the digestive tract. The muscularis layer is also a reliable suture line, and the serosal covering allows for a gas- and fluid-proof seal as a result of fibrin exudation within just 4-6 hours after intestinal suturing.

The large intestine plays a special role here. Its complication rate is higher because of various characteristics. This is due to low collateral circulation, the lack of serosal covering on parts of the ascending and descending colon and on the entire extraperitoneal rectum, and a lower mural collagen concentration in the large intestine with higher collagenase activity. In addition, since the concentration of bacteria increases by a factor of 10 million, there is a greater risk of infection. And anaerobes are 1,000 times more common in the large intestine than aerobic bacteria.

Leak-proof anastomosis by secure suturing is an indispensable part of abdominal surgery. All gastrointestinal sutures have two objectives: First, to restore a liquid- and gas-proof inner layer with the least ischemic effect possible on the transection margins. And secondly, to ensure resistance to all physical stresses and strains such as fluctuating intraluminal pressure, peristalsis, longitudinal tension and external pressure from adjacent organs. All of this should take place using a simple and rapid technique with the goal of minimizing contamination of the surgical field and implanting as little of the best tolerated foreign body material as possible.

Suture material causes foreign body reactions in the tissue; it supports and impairs healing at the same time. Animal studies on burst pressure confirm that the strength of an anastomosis decreases until the fourth day and then increases once again until normal levels are reached at around day 10.

Nevertheless, the suture material still acts as a foreign body that delays healing and increases the risk of pathogen infection. There are various options for decreasing this foreign body irritation Minimizing the mass of suture material to be implanted, use of absorbable substances persisting only for the duration of the actual load bearing function, and use of materials with only a low potential for irritation.

As with other wounds, intestinal anastomoses heal in three phases, . Lasting until day 4, the first phase is characterized by exudation of fibrin and blood components. During this time, the mechanical strength of the suture depends on the suture material used. In the second phase from day 4 to 14, vessel and fibroblast proliferation dominate. During the next phase of several months, the layers of the intestinal wall will reorganize.