Anastomotic Leak

Anastomotic complications are challenging clinical scenarios that are often associated with a temporary or permanent stoma, significant morbidity and 3% to 14% perioperative mortality. They are associated with decreased quality of life and prolonged disability, and are associated with higher healthcare resource utilization and cost.[1][2] Anastomotic leaks after rectal cancer resection are associated with decreased overall and cancer-specific (42% vs 67%) 5-year survival.[1]

The incidence of anastomotic leaks (AL) ranges from 0.5 to 18% for colorectal, and 5 to 19% for coloanal anastomoses.[3] AL may be clinically and radiographically apparent between one to seven days postoperatively but up to 50% are diagnosed after discharge and 12-30% are identified more than 30 days after surgery.[1][4][5][6] Small AL in the early postoperative period may be associated with low-grade fever and/or ileus while larger anastomotic defects may cause peritonitis and systemic sepsis. Patients with late leaks may present with insidious symptoms of pelvic pain and failure to thrive.[1][4][5][6] Clinical presentations vary because there is a spectrum of AL severity from minor staple line disruption to complete anastomotic dehiscence. Low colorectal/coloanal AL may present with less peritoneal inflammation than colorectal anastomotic leaks above the peritoneal refection. In addition, some AL may become walled-off by omentum or small bowel resulting in initial containment of peritoneal soilage with blunted and delayed clinical presentation.

Patient-related risk factors for anastomotic leak include distal colorectal location, diabetes mellitus, hyperglycemia, high HgbA1C, male sex, higher BMI, tobacco use, inflammatory bowel disease, chronic immunosuppressive medications, malnutrition, neoadjuvant radiation therapy, and advanced tumor stage.[1] The anastomosis should be without tension and with good blood supply. The need for blood transfusions may increase the risk for anastomotic leaks. Mechanical bowel preparation and oral antibiotics reduce the risk for anastomotic leaks. The etiology of anastomotic leaks continues to require further study as they occur even when evidence-based perioperative guidelines are followed closely, patient risk factors are optimized, and intraoperative principles are strictly adhered to. The gut microbiome may have a role for anastomotic leaks in patients without other risk factors and is an area of active research.[1]

The impact of proximal fecal diversion at index total mesorectal excision (TME) on subsequent AL is not entirely clear.[7] The role of proximal fecal diversion at the time of TME depends on the level of the anastomosis and the clinical status of the patient. Proximal fecal diversion may decrease septic complications and reoperations due to leaks and many recommend diversion when the anastomosis is ≤ 6cm from the anal verge, especially in rectal cancer patients treated with neoadjuvant radiation. Proximal fecal diversion is not without complications, including acute kidney injury from high output loop ileostomies and the complications associated with stoma closure.[7] Therefore, risks and benefits are weighed for each patient.

C-reactive protein and procalcitonin and other acute phase reactant biomarkers have been studied in an effort to make an early anastomotic leak diagnosis. While there is no consensus, these biomarkers have reasonably good negative predictive value but lack positive predictive value. [8]Contrast enema and CT imaging are the most useful confirmatory diagnostic radiologic studies [Figures 2.1-2.2]. However, the diagnosis of AL at imaging is not always obvious and there is little consensus on confirmatory findings.[1] An early postoperative CT scan may show an obvious leak with pneumoperitoneum or extraluminal extravasation of oral or rectal contrast. However, CT imaging may also show rim-enhancing fluid collections or specks of free air that are equivocal for leaks.[1] When compared to contrast enema, CT scan has the added advantage of assessing the anastomotic defect circumferentially, detecting a contained leak or an abscess where there is no extravasation of contrast, and detection of other intra-abdominal fluid collections, an associated small bowel obstruction, and unrecognized bowel injuries. CT scan is most diagnostic when performed with intravenous, oral and rectal contrast. One study showed that CT scans with rectal contrast were associated with significantly more patients with contrast at the anastomosis when compared to CT scans without rectal contrast (81.7% vs 26.0%, p< 0.001). CT scans with rectal contrast are also associated with fewer false-negative scans (4.6% vs 18.0%, p=0.004), less mortality (4.6% vs 16.0%, p=0.006), and less failure to rescue (7.9% vs 19.5%, p=0.048).[9] For patients with a distal rectal anastomosis, the rectal catheter for delivering contrast is often positioned by the surgeon to minimize trauma and to optimize the flow of contrast through the anastomosis. It is also an opportunity to gently palpate the anastomosis for defects. Failure to diagnose an AL may result in a chronic sinus tract and cavity with long term sepsis or need for permanent stoma.

Figure 2.1

Figure 2.2

Initial management of patients with AL includes intravenous fluid resuscitation and broad-spectrum antibiotics. Patients with sepsis manifested by hemodynamic instability and diffuse peritonitis are prepared for emergent exploratory laparotomy while those more stable clinically may undergo imaging with CT or contrast enema in an attempt to confirm the diagnosis and consider CT-guided intervention. While the optimal treatment for a patient with specific clinical presentations of AL are currently being evaluated in collaborative surgical trials[10], the surgeon must first establish sepsis source control and then determine if the anastomosis can be salvaged or if it requires resection. This management decision is best guided by assessing multiple clinical factors [Table 1] that include:

1) physiologic status of the patient - hemodynamic instability, fluid status, and requirement for vasopressors

2) patient-specific factors - frailty, nutritional status, physiologic reserve, comorbid conditions, preoperative continence for stool status, ASA grade, tobacco use, immunosuppressive medications, initial surgical indications/goals, presence of a protective ileostomy, and the potential need for additional treatment (e.g., chemotherapy for a malignant diagnosis)

3) operative findings - condition of the anastomosis (i.e. size of the anastomotic defect, presence of perianastomotic abscess, concomitant tissue ischemia/necrosis), location of the anastomosis (intraperitoneal vs. extraperitoneal) and degree and severity of peritoneal contamination (localized vs. diffuse, purulent vs. feculent)

These factors help guide surgical decision-making that determine if the AL should be resected with an end-colostomy or if the anastomosis can be potentially salvaged with concomitant proximal diversion.