Manual anastomoses in the gastrointestinal tract
Wound healing in the gastrointestinal tract is a complex process at the cellular and biochemical level. There are three distinct overlapping phases: Exudation, proliferation and repair.
In the gastrointestinal tract the initial exudative phase with edema and local inflammation lasts about 4 days [1]. It begins with the serosal surfaces of an intestinal anastomosis adhering to each other through fibrin exudation, thereby establishing a gas- and liquid-proof seal within the first 4 to 6 hours. The mechanical strength during this first phase of anastomotic healing is primarily provided by the suture material. The small intestine reacts much faster than the large bowel to violations of intestinal integrity, which is reflected in the rapid increase in collagen concentration and explains why colorectal anastomoses have a higher risk of failure [2]. Anastomotic healing during this phase is critical and can result in early failure around postoperative day 3–5.
The proliferative phase lasts about 14 days and is characterized by the increasing proliferation of fibroblasts and muscle cells as well as collagen formation; this increases the strength of the anastomosis so that its tensile strength no longer solely depends on the suture material. Neoangiogenesis also takes place during this phase. It begins around postoperative day 4–5 and essentially starts in the submucosa. At the end of the proliferative phase, mucosal defects have healed completely. The collagen-rich submucosa is the actual load-bearing part of the intestinal wall during this phase. While the anastomosis reaches the same level of burst pressure resistance as the intact bowel after about 10 days, its maximum tensile strength plateaus only after 4 to 6 weeks [3].
Final remodeling of the wall layers across the anastomosis takes place during the reparative phase. This phase may last several months and – assuming undisturbed anastomosis healing – gives the anastomosis the mechanical strength of intact bowel [4].
The absolute prerequisite for a successful anastomosis is sufficient mobilization and thus a tension-free juxtaposition of the intestinal ends with good blood supply. Extensive dissection results in poor blood supply and should therefore be avoided, as should aggressive resection of epiploic appendices of the colon, since at times these are terminal arteries.
Anastomotic technique
Hand-sutured anastomoses are documented descriptively according to a defined terminology. Sutures are characterized by the number of rows fashioned and by the layers penetrated by the needle. Wound edge approximation is classified as planar (flat), everted or inverted. In principle, all sutures may either be fashioned as interrupted sutures or as a running (continuous) suture. One common suture technique is the single-row running extramucous bilateral suture (armed with two needles). The latter is less expensive than interrupted sutures, introduces a smaller amount of foreign material and is easy to learn [5]. Convincing data from animal studies have been published for the single row running suture [6].
Inverting suturing was introduced by Jobert (1822) and Lembert (1826) and is based on the realization that serosal surfaces adhere quickly, thereby providing greater protection against anastomotic failure. The layered planar adaptation of the intestinal wall was studied in the early1950s, among others by Gambee, who described such a single-row suturing technique in 1951. Allgöwer also advocated layered planar sutures, which were neither inverting nor everting, for which good clinical results have been demonstrated [7]. Secure single-row planar sutures rapidly restoring the blood supply require a technique which is gentle on the tissue, stitching that adapts the intestinal edges well without ischemia and a secure knot tying technique. The vital importance of the submucosa for neoangiogenesis was demonstrated in studies [6], and in 1970 Goligher also established the significance of mucosal inversion. In a randomized trial he was able to demonstrate that a suturing technique inverting the mucosa was superior to a technique in which the mucosa maintains external contact (everted) [8]. Eversion of parts of the mucosa during anastomosis frequent results in leakage, fistula and abscess formation at these locations.
Factors impacting anastomotic healing
The healing of anastomoses is governed by factors inherent in the surgical technique, the patient him-/herself and external parameters. Negative factors include:
- Lack of surgical experience, tension on the anastomosis, local ischemia, incorrect suturing technique, contamination of the surgical field,
- Condition of the patient, particularly age, obesity, underlying disorder (ileus, sepsis, diabetes), emergency situation, medication (immunosuppression),
- Choice of anesthetic [9], perioperative volume therapy, preoperative radiochemotherapy, patient preparation (positioning, laxative measures).
Impending anastomotic failure is associated with considerable morbidity and mortality [10, 11].
Side-to-end anastomosis
In end-to-end anastomosis, two terminal lumina are reunited at their opened ends. The lumina should roughly be of the same diameter, which reduces the risk of anastomotic stenosis.
End-to-end or side-to-end anastomosis
In end-to-side anastomosis, the terminal lumen of a section of a hollow viscus is anastomosed with another segment which has been opened laterally. This is indicated when the luminal diameters differ, e.g, in the downstream Roux-en-Y anastomosis after gastrectomy or partial gastric resection, in the esophageal jejunostomy after gastrectomy and in descendorectostomy after resection of the rectum.
Side-to-side anastomosis
Side-to-side anastomosis joins the lateral lumina of two segments of a hollow viscus aiming to fashion a large-bore anastomosis when both ends are small-bore. Examples are gastrointestinal procedures bypassing malignant stenoses, Braun enteroenterostomy and fashioning a reservoir, e.g., after proctocolectomy in ulcerative colitis.