The primary concern in difficult bowel reconstruction is a tenuous and unsafe anastomosis. Multiple studies have demonstrated both “local” and “systemic” factors that contribute to poor anastomotic healing [1–4]. During an operation, the surgeon has immediate control of the local factors and a tension-free anastomosis with adequate blood supply is the most critical technical point that needs to be achieved to decrease the risk of anastomotic leak. Successful mobilization of the small bowel and colon to create tension-free anastomoses or stomas requires a clear understanding of their anatomic attachments. These attachments include (1) embryonic fusion planes, (2) peri-organ “ligaments,” and (3) vascular pedicles that can be ligated to maximize mobility while preserving necessary blood supply (Fig. 31.1).

The small bowel is tethered to the posterior abdomen in an obliquely arranged mesentery that runs diagonally from the ligament of Treitz in the left upper quadrant to the right lower quadrant. The small bowel mesentery is usually very mobile with retroperitoneal fixation only at the ligament of Treitz and near the terminal ileum as it joins the retroperitoneal cecum and right colon. The right colon mesentery posteriorly abuts the right kidney, right ureter, and duodenum. After turning at the hepatic flexure, the transverse colon emerges from the retroperitoneum and its mesocolon is usually mobile before fixation into the splenic flexure. At this juncture, the left colon becomes retroperitoneal and its mesentery posteriorly abuts the left kidney. The splenic flexure is additionally fixated by the greater omentum and several peri-organ “ligaments” (splenocolic, renocolic, pancreatocolic, and phrenocolic ligaments). The sigmoid colon is nonperitonealized and usually held by a few lateral attachments as its mesentery courses over the left ureter and gonadal vessels. As the tenia disappears, the rectum begins intraperitoneally at the sacral promontory before traveling under the peritoneal reflection with its mesorectum to the pelvic floor and anorectal junction.

While mobilizing the small bowel and colon from the retroperitoneum and peri-organ attachments such as the spleen and omentum is often sufficient to provide needed reach, these “first-line” maneuvers simply free, but preserve embryonic planes. Secondary and more advanced maneuvers exploit the vascular tethers within the mesentery. These vessels include the superior mesenteric artery (SMA) and its branches (the ileocolic, right colic, and middle colic artery), the inferior mesenteric artery (IMA) and its branches (the left colic, sigmoid, and superior rectal artery), and the inferior mesenteric vein (IMV). Thoughtful and directed transection of these vessels while relying on collateral blood flow can provide significantly more reach while maintaining a tension-free anastomosis with adequate blood supply.

Surgical trainees are taught that a successful anastomosis is one that is tension-free and well-vascularized. But is there a way to quantify how much tension is allowable for an anastomosis to be safe? Is there a way to quantify if adequate blood supply is reaching an anastomosis? These are critical questions that are always asked during mortality and morbidity conferences when presenting an anastomotic leak case, but unfortunately our ability to answer these questions with objective data is limited. On the contrary, we often rely on past experience and make clinical judgments when making these decisions.

Probably the simplest way to ask if an anastomosis is under tension is to lay the proximal and distal bowel ends in the field without any pulling or pushing. If the ends overlap each other by at least 5 cm, one can presume that there will be minimal to no tension on the anastomosis. When we need to pull inferiorly on the proximal end, or superiorly on the distal end, there will be problems and further mobilization needs to be performed. Similarly, during ileal-pouch anal anastomoses (IPAA), we use the inferior edge of the pubis symphysis as a rough estimate of adequate length if the apex of the pouch can reach it without tension.

Blood supply can be initially assessed with the gross appearance of the proximal and distal ends of the bowel. Completely ischemic tissue will have an obvious black-blue, discolored appearance, but this assessment is easiest at the extreme end of ischemia. In reality, bowel ends could be bruised, or “dusky,” and a clinical judgment needs to be made on its viability. In these cases, we observe whether there was bleeding at the anastomotic line during transection or use the Doppler to assess for blood flow. While somewhat rudimentary, we find these methods useful in those moments of doubt. Future diagnostic tests may include using intraoperative indocyanine green (ICG) angiography, which shows promise in distinguishing anastomotic ends with poor perfusion [5].

When presented with the bowel that cannot reach, mobilization should begin in a sequential and logical fashion that uses defined technical principles to remove anatomic constraints (Table 31.2). Primary maneuvers include (1) mobilizing embryonic planes and (2) dividing peri-organ “ligaments” or attachments. Secondary maneuvers include directed ligation of vascular pedicles that restrict the mobility of the corresponding proximal bowel. Often, these vascular ligations are already part of the oncologic resection. Tertiary maneuvers include more extended bowel resections to reach a mobile proximal portion of bowel versus the construction of a stoma if no tension-free option is possible. To illustrate these principles, we describe several challenging operative situations in which multiple strategies may be necessary to achieve intestinal continuity.