Small Bowel Bypass With Ileoiloeal Anastomosis and Mucous Fistula

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Small Bowel Bypass
With Ileoileal Anastomosis
and Mucous Fistula

In those cases where the small bowel is involved with obstruction and/or fistula formation following total pelvic irradiation and/or advanced malignant disease is impacted in the true pelvis, a bypass with mucous fistula rather than a bowel resection is the operation of choice. After small bowel resection, patients frequently develop (1) recurrent small bowl obstruction from adherence of the anastomosis site to the large raw dissected areas within the true pelvis, or (2) recurrent fistula formation at the site of anastomosis, or (3) breakdown of the closure of multiple inadvertent enterotomies associated with the surgery.

We have preferred bypass with end-to-end anastomosis and mucous fistula rather than the side-to-side anastomosis technique. Although the side-to-side anastomosis is more aesthetically acceptable to the patient, it is frequently associated with recurrent obstruction and persistent fistula drainage because it does not isolate the diseased portion of small bowel. The end-to-end or end-to-side technique of small bowel bypass requires a mucous fistula with an abdominal stoma that eventually contracts, produces small amounts of mucus, and has a lower incidence of recurrent obstruction and fistula drainage.

Physiologic Changes. In this operation, continuity of the intestine is established, and the patient is able to regain oral alimentation. With loss of the terminal ileum, however, fat-soluble vitamins and high-molecular-weight fat absorption can be disturbed, and postoperative diarrhea is frequently encountered. These undesirable side effects can be reduced with modification of the patient's diet. Vitamins can be replaced either systemically, as for vitamin B12, or by therapeutic oral supplementation, as for vitamins A, D, E, and K, which will be absorbed by the proximal intestine. The mucous fistula may drain excessively until the pathologic indication for the bypass has been relieved. One month postoperatively, mucous drainage is usually scant, and most patients wear only a small gauze dressing over the mucous fistula stoma site.

Points of Caution. We have found that the segment of bowel to be brought out as the mucous fistula stoma is optional. From a physiologic point of view it would seem that the peristaltic end of the segment should be used. If additional dissection is required to bring out the peristaltic end of the segment, however, the antiperistaltic end can be brought out as the mucous fistula stoma with equal effect.

Caution should be taken to ensure the vascular integrity of the terminal ileum. The blood supply to the terminal 10 cm of ileum is unreliable. This is particularly true if the patient has received total pelvic irradiation. If there is any doubt as to the integrity of the blood supply in the terminal ileum, the ileoileal anastomosis should be abandoned, and an ileoascending colostomy should be performed.

Technique

The abdomen is opened through a lower midline incision extended around the umbilicus, and the peritoneal cavity is entered. The afferent and efferent loops of intestine associated with the diseased segment of bowel are identified. The efferent loop will generally be grossly distended because most patients have some degree of obstruction, even in ileovaginal fistula formation. This afferent loop will be smaller and can generally be traced back from the ileocecal area without significant dissection. The purpose of this entire operation can be defeated, however, if the surgeon insists on total identification of all loops prior to the bypass procedure.

The dilated efferent proximal segment of bowel is elevated with rubber-shod clamps at a sufficient distance form the diseased segment. This is usually at the site that does not require dissection of the bowel into the true pelvis. The mesentery of the bowel is opened, and the vessels are clamped and tied. The bowel is transected in an oblique manner.

The distal segment or afferent loop is likewise elevated, its mesentery is opened, and the vessels are transected and tied. The bowel is transected in an oblique manner. Thus the diseased segment of bowel, impacted deep in the true pelvis, is isolated.

Some surgeons prefer to exteriorize both ends of the diseased segment of bowel as a double mucous fistula. We have not found this necessary, however, and multiple abdominal wall stomata only add to the aesthetic burden for the patient. The end of the diseased segment to be left in the lower abdomen and pelvis is closed with the automatic surgical stapler or with synthetic absorbable suture in the Gambee technique. Either the peristaltic or the antiperistaltic end can be closed, and the opposite end can be exteriorized as the mucous fistula.

The proximal (P) and distal (D) segments of healthy bowel are now anastomosed by either the suture technique, as described in small bowel resection with the Gambee anastomosis, or by the automatic surgical stapler technique, as described in Colon. Note that the diseased segment of intestine has been closed with the surgical stapler and is left densely impacted within the pelvis. Thus, no longer raw areas of dissection are available to which the new anastomosis might adhere. In addition, multiple inadvertent enterotomies, with their intestinal spillage, have been avoided.

The ileoileostomy has been performed with either the suture technique or the stapler technique. The abdomen has been closed, and the most convenient end of the diseased segment of intestine has been exteriorized through the lower midline incision of the abdominal wall closure. Note that the opposite end of the diseased segment has been closed off and left impacted within the pelvis. For demonstration purposes, the diseased segment represented here shows the pathologic condition alone. The reader should imagine that this segment is much longer with many entangled loops of intestine dipping deep into the pelvis, as shown in Figure 1.