Perioperative management - Anastomosis technique, gastrointestinal, with circular stapler

A gastrointestinal anastomosis is defined as a connection between two hollow viscera or regions of an organ, with the goal of viscerosynthesis, i.e., an anatomical and physiological reconstruction.

The correct suture technique is a fundamental requirement for the success of surgery. 

There is no binding standard for creating a gastrointestinal anastomosis. The correct technique is determined on an individual basis. 

By contrast, the requirements for an ideal anastomosis are clearly defined:

• Flawless anastomosis technique
• Good arterial and venous perfusion
• Lack of tension
• Clean surgical field

If any of these requirements is lacking, any compromise will  raise the risk of suture line failure with all its consequences.

The serosal surfaces of an intestinal anastomosis adhere due to fibrin exudation, normally within the first 4-6 hours, and will result in a gas- and fluid-proof seal. In this first phase of anastomotic healing the mechanical strength is primarily provided by the suture material.

The small intestine with its more rapid collagen production responds much faster to damaged intestinal integrity than does the large intestine, and this may explain the higher rate of early suture line failures in colorectal surgery.

Neovascularization starts on postoperative day 4 to 5 and essentially proceeds from the submucosa, the layer of the intestinal wall carrying the vessels. In this phase of wound healing, the submucosa with its abundance of collagen anchors the suture. The suture gains purchase here during that phase.

Adequate mobilization for tension-free apposition of well-perfused ends of the intestine is an absolute requirement. Extensive skeletonization must be avoided.

In hand-sutured anastomoses the layer count specifies the number of suture layers, while the thickness tells how much of the intestinal wall is penetrated during suturing.

Mechanical staplers as an alternative to handsewn sutures are used in almost  all areas of gastrointestinal surgery.

According to current evidence, when used correctly, handsewn and mechanical anastomoses in the lower gastrointestinal tract do not differ in terms of quality.

Surgical staplers are mechanical suturing devices fashioning a standardized multi-layer full-thickness sutures line. U-shaped titanium staples are pressed into the tissue in 2 or 3 staggered rows and then closed to a B-shape by bending the staple tips on an anvil. After firing the open B-shape of the staples allows passage of vessels up to 0.8mm in diameter and ensures good strength of the anastomosis and optimal perfusion. Before firing the mechanism, the tissue must first be compressed for 10-20 seconds to allow tissue to compress and thus fluid to escape. Different cartridges are available for various organ regions and tissue thickness.

In principle, there are 3 types of staplers:

• Linear staplers without a blade
• Linear cutters (staplers with blade)
• Circular staplers (EEA staplers with blade).

These are almost exclusively single-use instruments.

Linear staplers

Linear staplers are used primarily for partial or total closure of hollow viscera. Various staplers with cartridge lengths between 30 mm and 90 mm are available on the market, depending on the intended use. Whether instruments with 3.5 mm or 4.8 mm staple height are used depends on the thickness of the tissue to be closed. Cartridges with 2.45 mm staples are also available for closing vessels. 

Circular staplers

Circular staplers ([circular] end-to-end anastomosis [(C)EEA] stapler) consist of a shaft and head with a detachable anvil. EEA staplers are used in the lower GI tract primarily for reconstruction of intestinal passage after sigmoid or rectal resections.

Detachable stapler anvils with diameters of 21-33 mm allow individual adjustment to the intraoperative situation. Prior to use, both stumps must be closed with a purse-string suture or stapled closed. Alternatively, a purse string clamp may be used. For side-to-side anastomoses, one of the two purse-string sutures can be omitted if the mandrel on the mounting shaft of the stapler directly perforates the intestinal wall. When there is tissue contact, firing the stapler creates a circular staggered double row of staples with central excision of the inverted tissue. Once the stapler is partially opened, it is easily pulled back together with the anvil.

The anastomosis should always be tested for leakproofness . This can be performed by instilling some air ("inner bicycle tube test"). It is also essential to check both anastomotic donuts for integrity to ensure that the anastomosis is intact. The results of both tests should also be noted  in the patient’s surgical note. Distal transection of the bowel with a linear stapler and subsequent reconstruction with the EEA stapler is also known as "double-stapling".

Apart from transanal insertion, the circular stapler must otherwise be introduced via a separate enterotomy or an already open intestinal lumen (e.g., esophagojejunostomy).