Manual Anastomoses in the Gastrointestinal Tract
Wound healing in the gastrointestinal tract is a complex process at the cellular and biochemical level. Three overlapping phases are distinguished: the exudative, proliferative, and reparative.
The initial exudative phase with edema and local inflammation lasts about 4 days in the gastrointestinal tract [1]. It begins with the adhesion of the serosal surfaces of an intestinal anastomosis through fibrin exudation, which leads to a gas- and liquid-tight closure in the first 4 to 6 hours. The mechanical strength in this first phase of anastomosis healing is primarily provided by the suture material. The small intestine reacts to injuries to intestinal integrity much faster than the large intestine, which is reflected in the rapid increase in collagen concentration and explains why colorectal anastomoses have a higher risk of insufficiencies [2]. Anastomosis healing is critical in this phase and can lead to early insufficiencies around the 3rd to 5th postoperative day.
The proliferative phase lasts about 14 days and is characterized by the increasing proliferation of fibroblasts and muscle cells as well as collagen formation, which increases the strength of the anastomosis, so that its tensile strength is no longer solely dependent on the suture material. Neoangiogenesis also falls into this phase. It begins around the 4th to 5th postoperative day and essentially originates from the submucosa. At the end of the proliferative phase, mucosal defects are completely healed. The collagen-rich submucosa is the actual suture-bearing wall component in this phase. After about 10 days, the anastomosis achieves resistance to bursting pressure comparable to that of the intact intestine, whose maximum tensile strength is only reached after 4 to 6 weeks [3].
In the reparative phase, the final remodeling of the wall layers across the anastomosis occurs. This phase can last up to several months and leads - assuming undisturbed anastomosis healing – to the mechanical strength of intact intestine [4].
An absolute prerequisite for a sufficient anastomosis is adequate mobilization and thus tension-free approximation of well-perfused intestinal ends. Extensive skeletonizations lead to inadequate perfusion and should therefore be avoided, as should aggressive removal of appendices epiploicae of the colon, as these occasionally represent end arteries.
Anastomosis Technique
Hand-sewn anastomoses are descriptively captured according to a defined terminology. The row count indicates the number of suture rows, the layer count the wall layers penetrated by the suture. The adaptation technique of the wound edges is described as end-to-end, inverting, everting, and invaginating. In principle, all sutures can be performed either in single-button technique or as a continuous suture. The continuous, single-row, extramucosal suture with double-armed thread is frequently used. The latter is more cost-effective compared to the single-button suture, introduces a smaller amount of foreign material, and is easy to learn [5]. Convincing animal experimental data exist for the single-row continuous suture [6].
Inverting suture techniques were introduced by Jobert (1822) and Lembert (1826) and are based on the recognition that serosal surfaces adhere quickly and this provides greater security against insufficiencies. The layer-appropriate adaptation of the intestinal wall end-to-end was investigated in the early 1950s, among others by Gambee, who described such a single-row suture technique in 1951. Layer-appropriate, neither inverting nor everting sutures were also promoted by Allgöwer and supported by good clinical results [7]. Prerequisite for a secure single-row end-to-end suture, which leads to rapid restoration of vascular supply, are tissue-sparing preparation technique, a stitch placement that achieves good adaptation without ischemia of the intestinal edges, and a secure knotting technique. The central importance of the submucosa for neoangiogenesis has been demonstrated in studies [6], as has the importance of mucosal inversion in 1970 by Goligher. He showed through a randomized study that the suture technique with submersion of the mucosa (inverting) is superior to a technique in which the mucosa maintains external contact (everting) [8]. The eversion of mucosal portions during anastomosis leads to increased leaks, fistulas, and abscesses at these sites.
Influencing Factors on Anastomosis Healing
Surgical-technical, patient-specific, and external factors influence anastomosis healing. Negative factors include:
- lack of surgical experience, tension at the anastomosis, local ischemia, incorrect suture technique, contamination of the operative field,
- patient's condition, especially age, obesity, underlying diseases (ileus, sepsis, diabetes), emergency situation, medication (immunosuppression),
- choice of anesthetic agent [9], perioperative volume therapy, preoperative radiochemotherapy, patient preparation (positioning, laxative measures).
A threatening anastomosis insufficiency is associated with significant morbidity and lethality [10, 11].
End-to-End Anastomosis
In the end-to-end anastomosis, two terminal lumina are reunited at their opened ends. The lumina should have a comparably large diameter, which reduces the risk of anastomosis stenosis.
End-to-Side resp. Side-to-End Anastomosis
In the end-to-side anastomosis, the terminal lumen of a hollow organ segment is anastomosed with another laterally opened segment. The indication arises with different lumen diameters, as is the case, for example, with the foot point anastomosis in Y-Roux reconstruction after gastrectomy or partial gastric resection, esophagojejunostomy after gastrectomy, or descending rectostomy after rectal resection.
Side-to-Side Anastomosis
The side-to-side anastomosis unites the lateral openings of two hollow organ segments with the goal of a large-lumen anastomosis with small-lumen ends. Examples are gastrointestinal bypass operations to bypass malignant stenoses, the foot point anastomosis according to Braun, as well as the reconstruction of a reservoir, e.g., after proctocolectomy for ulcerative colitis.