The technical details associated with small bowel anastomosis such as stapled versus hand-sewn or end-to-end versus side-to-side have been extensively studied and reveal that there is no unmistakably superior method. The best tactic to decrease leak rates is meticulous attention to the technical details in whichever technique is preferred by the surgeon. Tension-free anastomosis with a healthy blood supply is critical in a successful anastomosis. The creation of the suture line should be performed while avoiding overtightening. Excessively tight suture lines may lead to focal ischemia and subsequent leak.

Identification of anastomotic leaks in the small intestine is typically identified by CT with oral contrast [1]. Dependent upon the clinical situation, fluoroscopic studies can be of benefit; small bowel follow through can provide dynamic information, while fistulogram can help delineate the precise loop of bowel associated with an enterocutaneous fistula.

Early anastomotic leaks in the small intestine will typically present in a dramatic fashion and should typically be managed operatively, notably in the setting of peritonitis, sepsis, or hemodynamic instability. The presentation of an early anastomotic leak typically indicates a technical failure and should usually be addressed surgically. The limited presence of adhesions early in the postoperative course can make resection of a failed anastomosis and fresh anastomosis an often successful course of management. The distance from typical endoscopic routes of entry makes endoluminal therapies less feasible in small bowel fistulae.

Late anastomotic leaks in the small intestine can be very difficult to manage operatively given the dense adhesive burden in a postoperative abdomen. Factors leading to late development of anastomotic leaks include anastomoses under tension, deserosalized bowel, and suture hematomas. Factors preventing spontaneous closure of leaks are remembered by the mnemonic FRIENDS: Foreign bodies, Radiation, Infection/inflammatory bowel disease, Epithelialization of the tract, Neoplasm, Distal obstruction, Short fistula tracts less than 2 cm. The presence of abscesses adjacent to an anastomotic leak can further prevent spontaneous closure of fistulae.

Imaging can be indispensable in the patient with late anastomotic leakage in delineating anatomy and identifying drainable collections. Intra-luminal and intravenous contrast enhanced CT scans can identify abscesses as well as fistula anatomy. Contrast enhanced fluoroscopy studies such as UGI or fistulograms can provide additional information if CT imaging is not clear.

Late anastomotic leaks often present as enterocutaneous fistulae (ECF) and can manifest in several ways. The finding of an intra-abdominal abscess requiring percutaneous drainage can then begin draining enteric contents. Postoperative wound infections, opened at bedside, can also begin leaking succus. Spontaneous drainage through the skin may occur in leaks that occur near the abdominal wall. Given that non-operative management is often attempted first, patients may undergo significant daily fluid and electrolyte losses, notably potassium, sodium, phosphate, and magnesium. Proximal fistulae can lead to metabolic acidosis due to loss of bicarbonate. Fistula output can be classified as low (<500 cc/day) or high output (>500 cc/day).

NPO, parenteral nutrition, antibiotics, and percutaneous drainage are the first line of treatment in management of late anastomotic leaks. Percutaneous drainage can be invaluable in the management of late anastomotic leaks of the intestine. Serial CT scanning to assess adequacy of drainage should be undertaken with drain upsizing as needed to accomplish source control. The addition of octreotide can also reduce fistula output though with no proven effect on outcomes. One early study blinded octreotide administration and found that patients off octreotide had output averaging 698 ml/day with a reduction to 246 ml/day after two days of octreotide [16]. Octreotide has also been demonstrated to shorten the time to closure of fistula [17]. Low output fistulae will often respond to these measures alone. Enteral nutrition may be considered in patients with low output fistulae. If PO intake is tolerated and the output does not increase, then enteral feeding may be used in lieu of TPN. Nutritional support is critical to the success of spontaneous fistula closure, and requirements are typically closer to 30 kcal/kg/d in patients with high output fistulae [18]. In patients who are severely malnourished, gradual initiation of nutritional support should be undertaken to prevent refeeding syndrome.

Fistula output is typically caustic and can lead to significant skin complications. Early utilization of drainage management systems, ideally with the assistance of a stomal therapist, should be attempted. Vacuum-assisted dressings are frequently used to isolate fistulas and reduce soilage of adjacent skin.

Closure of enterocutaneous fistulae will ideally occur spontaneously. This can require a great deal of patience from both the patient and the surgeon. A wide range of spontaneous closure rates for intestinal fistulae are reported from 20 to 90 % [19–22]. The above-mentioned modalities should be exhausted in the interim while waiting a minimum of three months before attempting surgical control of ECF. This will permit reduction in the dense adhesions often seen in this setting and reduce the risk of serosal injuries or enterotomies. Early operation can lead to life-threatening blood loss from highly vascular adhesive tissue that can be difficult to control due to the dense fused visceral block.

Undertaking surgical correction of ECF requires a great deal of planning and patience. Ideally, mobilization of the entirety of bowel is crucial to eliminate points of obstruction. Once the bowel is mobilized, resection of the affected segment is undertaken. Ensuring that there is healthy tissue covering the entirety of the bowel is critical to prevent further leaks. Meticulous repair of the inevitable serosal tears or enterotomies encountered during adhesiolysis is mandatory.

Anastomotic leaks can also manifest in the open abdomen as enteroatmospheric fistulae (EAF). Management of EAF is extremely challenging to even the most experienced surgeon and close attention should be paid to techniques that can minimize risk of fistula formation. Wound care of the open abdomen should not be relegated to junior members of the surgical team as aggressive dressing changes or missed subtle findings can lead to months of further complications. Placement of the omentum over exposed bowel can protect the bowel from overlying dressings. Avoiding the placement of gauze or vacuum sponges directly on bowel is important to prevent fistula formation. We use polyglactin (Vicryl) mesh if unable to close an open abdomen. Eventual placement of autologous skin grafts allows formation of a suitable barrier that minimizes desiccation of the underlying bowel. Placement of the skin graft should only be undertaken once a suitable bed of granulation tissue forms—typically around 10–14 days.

EAF present a challenge from a wound care standpoint. Given that the fistula is often in the midst of fused loops of bowel, applying ostomy appliances directly to the loop of bowel is undesirable and preventing spillage of enteric contents across the visceral block can be challenging. Proximal diversion, while appealing, can be difficult due to foreshortening of the mesentery preventing an ostomy from reaching the skin. The initial goal of wound care in EAF should be attainment of granulation or coverage of the surrounding open abdomen. This can be accomplished several ways. Vacuum-assisted closure can be attempted, though care must be taken to cover the exposed bowel with a barrier such as petrolatum gauze or plastic sheets. Some concerns exist about this technique increasing fistula output due to negative pressure. The floating stoma, as originally described by Subramaniam et al. [23], entails placement of a plastic sheet over the exposed bowel with a hole cut overlying the fistula. This opening is then sutured to the bowel, encircling the fistula and preventing effluent from spilling onto the exposed bowel. A stoma appliance can then be applied to the fistula and changed as needed.

After a suitable containment solution has been found for the fistula, the surrounding bowel should be covered with a split thickness skin graft. Once the skin graft incorporates, a simple stoma appliance can be applied over the fistula and then treated as an ileostomy. Eventual closure of the abdominal wall can be undertaken once the skin graft passes the “pinch test”; once the grafted skin can be pinched up and off the underlying bowel, it is ready for resection and abdominal wall closure with attendant resection of fistula and anastomosis in a non-inflamed field.