Enteroenterostomy

Enteroenterostomy is an anastomosis between one part of the small bowel and another part of the small bowel (jejunum or ileum). It is used to restore bowel continuity after resection of a segment of the bowel or after creation of a Roux-en-Y loop of jejunum or as a part of a Braun loop of jejunum. When performed as a bypass procedure, enteroenterostomy relieves bowel obstruction.[1, 2]

An enteroenterostomy is more often performed in an emergency setting (eg, obstruction or trauma) than in an elective setting.

Enteroenterostomy is indicated for the following:

• After resection of small intestine (eg, for inflammatory bowel diseases such as tuberculosis, Crohn disease, malignancy [primary of the small bowel, such as adenocarcinoma or lymphoma; infiltration of the small bowel by a malignancy of an adjacent organ, such as the colon], ischemic stricture, trauma)
• For intestinal bypass (short circuit) to relieve obstruction (though it is not preferred, in that it may result in blind-loop syndrome) or after closure of a perforation (eg, an enteric perforation from typhoid)
• As a part of a Roux-en-Y loop or Braun loop of jejunum (used for biliary-enteric, pancreaticoenteric, or esophagoenteric anastomosis and as a part of gastric bypass as a bariatric procedure) ^{[3, 4, 5, 6, 7]}
• Braun enteroenterostomy is a side-to-side anastomosis between the afferent and efferent limbs of jejunum distal to a biliary-enteric, pancreaticoenteric, esophagoenteric, or gastroenteric anastomosis, diverting the jejunal anastomosis from the aforementioned anastomoses 
• Endoscopic ultrasonography (EUS)-guided enteroenterostomy (EUS EE) has been reported to be effective in the management of afferent loop syndrome following a gastrectomy or gastrojejunostomy recontruction ^[8]

Contraindications for enteroenterostomy include the following (which are contraindications for performing any bowel anastomosis in general):

• Poor nutritional status (severe pallor, pitting pedal edema, low serum albumin levels)
• Significant hypotension during operation, irradiated bowel
• Poor blood supply to the bowel ends
• Thick edematous obstructed or inflamed bowel ends (sutures cutting through)

In case of doubt, it is better not to anastomose but rather to exteriorize (loop stoma for a perforation and proximal stoma and distal mucous fistula after resection).

Best practices

Several steps can help promote better outcomes during enteroenterostomy:

• No tension (though tension is usually not a problem in the small bowel unless its mesentery is shortened, thickened, and inflamed)
• Good blood supply of the bowel ends - This may require resection of a larger segment of bowel or repeat resection of a doubtfully viable bowel
• Good (water-tight) approximation
• No mucosal eversion between approximated bowel walls; the mucosa should be intentionally inverted - This can be achieved by avoiding mucosa or taking a very small amount of mucosa in suture bites
• Serosa (visceral peritoneum) should be approximated
• In case of an end-to-end enteroenterosotomy, the mesenteric angle (bare area) should be carefully covered with peritoneum - This can be done by taking a U (box) stitch that includes both layers of small-bowel mesentery.
• No distal obstruction

Procedural planning

Most small-bowel anastomoses are performed in the emergency setting in patients with intestinal obstruction. A nasogastric tube is inserted to decompress the stomach (and proximal dilated small bowel). Fluid and electrolyte imbalances should be corrected. Intravenous (IV) human albumin (100 mL of 20% albumin twice a day) may be used to increase the oncotic pressure and take care of the bowel wall edema. Bowel preparation is not required for small-bowel resection and anastomosis (as opposed to large-bowel resection and anastomosis, in which bowel preparation is required).

Complication prevention

An anastomotic leak is a life-threatening complication that can cause sepsis (fever, tachycardia, hypotension), abdominal signs of guarding and tenderness, multiple organ dysfunction syndrome (MODS), and even death (mortality, 10-15%). The leak is initially small but results in a local abscess that erodes into the rest of the anastomosis or spreads into adjacent structures (including vessels) to cause bleeding.

A localized leak manifests as undue or prolonged pain, unexplained fever, and unsettled abdomen with localized tenderness and paralytic ileus. A major free leak causes peritonitis; it may also present as an enterocutaneous fistula (ie, enteric contents protruding through the wound) or wound disruption (dehiscence)

Because an anastomotic leak is difficult to detect in obese and elderly patients, a high index of suspicion is necessary. In case of doubt, it can be confirmed by means of computed tomography (CT) with IV and oral (water-soluble) contrast (Gastrografin).

Anastomotic leakage almost invariably necessitates reoperation; dismantling of anastomosis and exteriorization (proximal stoma and distal mucous fistula) should be performed. No sutures should be used in an attempt to close (repair) the anastomotic leak, because the sutures are unlikely to hold and tend to cut through, further enlarging the leak.

Other potential complications include the following:

• Anastomotic narrowing caused by too much inversion of walls - This is likely to be a greater problem in a two-layer end-to-end anastomosis
• Blind-loop syndrome in bypass and side-to-side anastomosis

An enteroenterostomy restores bowel continuity after resection of a segment of the bowel or after creation of a Roux-en-Y loop of jejunum. When performed as a bypass procedure, enteroenterostomy relieves bowel obstruction.

Braun enteroenterostomy may reduce the risk of delayed gastric emptying (DGE) in pancreatoduodenectomy.[9]  A study by Watanabe et al found that the use of a lengthened efferent limb in a Braun enteroenterostomy decreased DGE by as much as 6%, leading to a shorter hospital stay.[10]

The patient should be informed about the possibility of an anastomotic leak and subsequent need for reintervention, including reoperation.

A fine (3-0 or 4-0) synthetic long-acting absorbable polyfilament suture (eg, polyglactin) on a small (20-mm) curved (half-circle) round-bodied needle is used for a single-layer intestinal anastomosis. For a two-layer anastomosis, the outer layer may be nonabsorbable and the inner layer absorbable.

A linear stapler (30 mm, 60 mm, 90 mm) or a transverse anastomosis (TA) stapler (30 mm, 45 mm, 60 mm, 90 mm) is used for closure of ends. A linear cutter (55 mm, 75 mm, 100 mm) or a gastrointestinal anastomosis (GIA) stapler (60 mm, 80 mm, 100 mm) is used for anastomosis. Note that the biofragmentable anastomotic ring (BFAR) is no longer used for enteroenterostomy.

Anesthesia

General anesthesia is required for enteroenterostomy.

Positioning

The patient should be in the supine position.

After the procedure, intravenous fluids should be started. Patients should be given nothing by mouth; oral clear fluids can be started the morning following surgery (unless obstruction or ileus was present), progressing to liquid diet, soft solids, and a normal diet over a few days.

A nasogastric tube is not required unless the patient has an intestinal obstruction or has peritonitis and ileus.

A mid-midline incision is best suited for enteroenterostomy. Enteroenterostomy as a part of gastric bypass surgery can also be performed laparoscopically with sutures or staplers. Enteroenterostomy can be done either in a single layer or in two layers; no significant difference has been found between the two approaches.

Enteroenterostomy may take the following three forms:

• End-to-end - The advantage with an end-to-end enterostomy is that there is only one suture line, in contrast to the two suture lines in an end-to-side anastomosis and the three suture lines in a side-to-side anastomosis; the disadvantage is that there is a luminal size disparity between the proximal dilated bowel and the distal collapsed bowel that may be difficult to manage, and the critical mesenteric angle (bare area) is more prone to anastomotic leakage
• End-to-side
• Side-to-side (ie, lateral) - This is used for bypass (short-circuit operation) but can be also be used after resection; the advantages are that the luminal size disparity is not a problem and that a large stoma can be created; a disadvantage is that the loop is blind

Handsewn vs stapled anastomosis

Anastomosis can be handsewn or stapled (a stapled anastomosis is quicker and ensures inversion of mucosa); no significant overall difference has been found between the two.[11] A stapled anastomosis is usually performed in a side-to-side fashion[12] by using a linear cutter or gastrointestinal anastomosis (GIA) stapler; it may also be done in an end-to-side manner. An end-to-end stapled anastomosis can be performed as well (the circumference is divided into three equal segments, each of which is closed with a linear stapler or a transverse anastomosis [TA] stapler).

Suture type

Interrupted or continuous sutures may be used for enteroenterostomy. Interrupted sutures cause less ischemia and ensure better adjustment of luminal discrepancy, but they take more time, use more suture material, and require more knots. A continuous over-and-over (running) suture is hemostatic, takes less time, uses less suture material, and requires fewer knots; however, a continuous suture leads to more ischemia.

Single-layer vs two-layer anastomosis

For a single-layer (seromusculosubmucosal, extramucosal) anastomosis, bites include all layers except mucosa (submucosa must be included). The advantages include less ischemia, less compromise (narrowing) of the lumen, and avoidance of mucosal eversion (extrusion).

A two-layer anastomosis includes the following:

• Posterior outer seromuscular (Lembert) sutures (usually interrupted but may be continuous)
• Posterior-inner all-layer (full-thickness) through-and-through (over-and-over) continuous (for better hemostasis) suture with intermittent (after every four or five bites) locking to avoid a purse-string effect
• Anterior-inner all-layer (Connell–full thickness, inverting, outside in and then inside out on the same bowel end with loop on mucosa) suture or through-and through continuous suture; the serosa is lifted with a fine nontoothed forceps so that mucosa falls back while the mucosa is being inverted by the assistant with a fine nontoothed forceps
• Anterior-outer seromuscular (Lembert) sutures (usually interrupted but may be continuous)

Another option is to start in the middle of the posterior layer with a double-needle suture; one half of the posterior layer is completed with one needle and the other half with the other needle. The suture then turns around both corners and continues in both halves of the anterior layer and meets in the middle of the anterior layer. Any gaps or bleeding points require additional interrupted sutures in between.

The mesenteric gap is then closed; bites include the peritoneum only and should avoid mesenteric vessels.

End-to-end anastomosis

Noncrushing soft intestinal clamps (preferably linen-shod) are used on the two divided ends to bring them together, to prevent spill of intestinal contents, and to provide temporary hemostasis from the cut bowel ends. However, they should not include and occlude the vessels in the mesentery. Thereafter, stay sutures are taken at two (mesenteric and antimesenteric) corners, and the mesenteric angle of sorrow (the bare area between two layers of mesentery) is closed with a horizontal U (box) stitch.

Luminal disparity

Disparities in luminal diameter or circumference between the proximal dilated bowel and the distal collapsed bowel can be handled in several ways, as follows:

• Interrupted sutures dividing each wall (posterior and anterior) into halves and then each half into further halves
• In a continuous suture, the distance between two consecutive bites should be smaller on the narrower lumen side and greater on the wider lumen side
• Cheatle maneuver - Longitudinal incision along the antimesenteric border on the narrow lumen to increase its circumference
• End (of the wider lumen) to the side (of the narrower lumen) anastomosis - the end of the narrower side is closed with sutures or staples
• Side-to-side anastomosis

Side-to-side anastomosis

Side-to-side anastomosis is done on the antimesenteric borders of the two loops; it avoids the mesentery and thus does not interfere with the blood supply.

Noncrushing soft intestinal clamps are used on the two divided ends. The anastomosis is usually done in two layers. Stay sutures are taken at two corners. Posterior outer seromuscular (Lembert) sutures (usually interrupted but may be continuous) are taken. The lumen should be opened about 5 mm from the seromuscular layer; this opening should be as close to the closed ends as possible to avoid a significant blind loop. Cautery can be used for opening the bowel (coagulating current for muscle and cutting for mucosa); contents are sucked and mopped.

The anastomosis includes the following:

• Posterior outer seromuscular (Lembert) sutures (usually interrupted but may be continuous)
• Posterior-inner all-layer (full-thickness) through-and-through (over and over) continuous (for better hemostasis) with intermittent (after every four or five bites) locking to avoid a purse-string effect
• Anterior-inner all-layer (Connell–full thickness, inverting, outside in and then inside out on the same bowel end with loop on mucosa) suture or through-and-through continuous suture; the serosa is lifted with fine nontoothed forceps so that mucosa falls back while the mucosa is being inverted by the assistant with a fine nontoothed forceps.
• Anterior-outer seromuscular (Lembert) sutures (usually interrupted but may be continuous)

Note that a drain is not required for enteroenterostomy.

Enteroenterostomy using compression anastomosis clips (CAC) has been described.[13] Endoscopic ultrasonography (EUS)-guided enteroenterostomy using a lumen-apposing metal stent (LAMS) has been described.[14]