Manual gastrointestinal anastomosis
Gastrointestinal wound healing is a complex process at the cellular and biochemical level. Three overlapping phases are distinguished: Exudation, proliferation, and repair.
In the gastrointestinal tract, the initial exudative phase with edema and local inflammation lasts about 4 days [1]. It starts by sealing the serosal surfaces of intestinal anastomosis through fibrin exudation, creating a gas- and fluid-proof seal within the first four to six hours. In this first phase of anastomotic healing, the mechanical strength is primarily provided by the suture material. The small intestine responds much more quickly to violations of intestinal integrity than the large bowel, which is reflected in the rapid increase in collagen levels and helps to explain why colorectal anastomoses are at higher risk of suture line failure [2]. Anastomotic healing is critical in this phase and may result in early suture line failure around postoperative day 3-5.
The proliferative phase lasts about 14 days and is characterized by increasing proliferation of fibroblasts and muscle cells as well as collagen formation, thus increasing the strength of the anastomosis that is now no longer reliant on the suture material alone. Neoangiogenesis also begins in this phase. It starts around postoperative day 4 to 5 and essentially proceeds from the submucosa. Mucosal defects will have healed completely by the end of the proliferative phase. In this phase, the collagen-rich submucosa is the actual part of the wall bearing the suture. While the burst pressure of the anastomosis reaches the level of the intact intestine after about 10 days, its maximum tensile strength will not be restored for 4 to 6 weeks [3].
Final remodeling of the wall layers across the anastomosis proceeds during the repair phase. This phase may last up to several months and results in the mechanical strength of an intact intestine - assuming the anastomosis heals unimpaired [4].
Adequate mobilization and thus tension-free apposition of well-perfused bowel ends is an absolute prerequisite for a reliable anastomosis. Extensive skeletonization impairs bowel perfusion and should therefore be avoided, as should aggressive resection of epiploic appendices of the colon, since these occasionally represent terminal arteries.
Anastomosis technique
Hand-sewn anastomoses are classified according to a defined descriptive terminology. The layering indicates the number of suture layers, and the bite thickness how deep the suture penetrates the wall. The edges of the intestinal stumps can be anastomosed in flush, everting, inverting, or telescope fashion. In principle, all sutures can be carried out either as interrupted or running sutures. One common technique is with a single layer, extramucosal, double-armed running suture. The latter is less expensive than interrupted sutures, introduces less foreign body material and is easy to master [5]. Convincing data from animal studies are available for the single-layer running suture [6].
The inverting suture techniques introduced by Jobert (1822) and Lembert (1826) are based on the knowledge that the serosa surfaces adhere quickly, thereby providing greater protection against anastomotic failure. The layered adaptation of the cut lumina flush with each other was investigated in the early 1950s, among others by Gambee, who described such a single-layer suturing technique in 1951. Layered sutures, neither everting nor inverting, were also propagated by Allgöwer, and corroborated by good clinical outcomes [7]. The prerequisites for a safe flush anastomosis by single-layer suturing, resulting in a rapid restoration of the blood supply, are a tissue-sparing dissection technique, stitching with good apposition of the edges without them becoming ischemic and a secure knot tying technique. Trials have affirmed the key role of the submucosa in neoangiogenesis [6] while Goligher demonstrated the significance of mucosal inversion in 1970. In a randomized trial, he proved that suturing with the mucosa inverted is superior to techniques in which the mucosa maintains external contact (everting) [8]. Those locations with mucosal eversion during anastomosis often resulted in leakage, fistulation, and abscess formation.
Factors influencing anastomotic healing
Anastomotic healing is affected by technical surgical, patient-related, and external factors. Negative factors Include:
- Lack of surgical experience, tension at the anastomosis, local ischemia, incorrect suturing technique, surgical field contamination,
- Condition of the patient, particularly (higher) age, obesity, underlying disease (ileus, sepsis, diabetes), emergency, medication (immunosuppression),
- Choice of anesthetic [9], perioperative volume therapy, preoperative radiochemotherapy, patient preparation (positioning, laxatives)
Any impending suture line failure is associated with significant morbidity and mortality [10, 11].
End-to-end anastomosis
In terminoterminal anastomosis, two terminal lumina are reunited at their cut edges. The lumen diameters should be of a similar size to reduce the risk of anastomotic stricture.
End-to-side and side-to-end anastomosis
In terminolateral anastomosis, the terminal segmental lumen of a hollow viscus is anastomosed with another segment opened laterally. This is indicated in lumina of different diameter, e.g., jejunojejunostomy in Roux-en-Y reconstruction following total or partial gastrectomy, esophageal jejunostomy following gastrectomy or descendorectostomy following rectal resection.
Side-to-side anastomosis
A laterolateral anastomosis unites the lateral segmental openings of two hollow viscera to fashion an anastomosis with a wide lumen when the lumina of both ends are small. Examples include gastrointestinal bypass procedures in malignant stenosis, Braun anastomosis, as well as fashioning a pouch, e.g., following proctocolectomy in ulcerative colitis.