Anatomy - Anastomosis technique, gastrointestinal, end-to-end, open, continuous, hand suture, in inverting technique

The wall structure of the large and small intestine is very similar. The low proportion of connective tissue and collagen fibers in the Tunica mucosa is responsible for the reduced mechanical load-bearing capacity of a mucosal suture alone.
The Tela submucosa, consisting of connective tissue with a three-dimensional scissor-grid-like arranged collagen fiber framework and elastic networks, forms in all parts of the digestive tract the supporting“ part of the intestinal suture. A reliable suture bed is also the Tunica muscularis, and the serosa covering enables through fibrin exudation a gas- and liquid-tight closure already 4-6 hours after intestinal suture.
In this, the large intestine plays a special role. Due to various peculiarities, the complication rate is higher here. Causes for this are a low collateral circulation, the missing serosa covering on parts of the ascending and descending colon as well as on the entire extraperitoneal rectum and a lower collagen content of the large intestine wall with higher collagenase activity. In addition, there is the greater infection risk due to the increase in bacterial concentration by a factor of 10 million. In addition, anaerobes are found in the large intestine 1000 times more frequently than aerobic bacteria.

The tight anastomosis through secure suturing represents an important part of abdominal surgery. The goal of every suture in the digestive tract is, on the one hand, the restoration of a liquid- and gas-tight inner layer with the least possible ischemic impact on the cut edges. On the other hand, it must ensure resistance to all physical stresses such as varying internal pressure, peristalsis, longitudinal tension, and external pressure from neighboring organs. All this should be achieved using simple and quick techniques with the aim of minimizing contamination of the surgical field as well as the implantation of few and optimally tolerated foreign bodies.
Suture material acts in the tissue as a foreign body; it supports and disrupts healing at the same time. Animal experimental studies show that the strength of an anastomosis, when tested for its bursting pressure, decreases until the fourth day and then increases again until normal values are reached around the 10th day.
Nevertheless, the thread material acts as a foreign body that delays healing and increases the risk of infectivity from pathogenic germs. To reduce this foreign body irritation, there are various possibilities: Keeping the mass of the suture material to be implanted low, using absorbable substances that remain only for the duration of the actual holding function, and using materials with only low irritation potential.
The healing of intestinal anastomoses proceeds like in other wounds in three phases. The first phase, lasting until the 4th day, 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 the 4th – 14th day, vascular and fibroblast proliferation dominates. In the third phase, lasting several months, the intestinal wall layers reorganize.