Anastomotic leaks after colon surgery: subtle signs, serious risks
Later recognition might portend worse outcomes
Anastomotic leaks after colon resection can be hard to detect, and late recognition can lead to sepsis, high-risk reoperations, and death.
Leaks probably occur less often today, thanks to improved surgical techniques, imaging studies, and increased vigilance among clinicians. Still, about 1 in 29 patients (~3.4%) experience an anastomotic leak within 30 days of colorectal surgery, with some cohorts approaching the historical rates of ~6%.
Risks increase with the location of the resection, with ileocolic/right-sided resections at the lowest risk, and very distal (low rectal) the highest risk for leaks. Emergency surgery for perforated bowel has a higher rate of leak than elective colon resections.
A recent cohort study in JAMA Surgery highlights the risk of deadly sepsis that can easily stem from unrecognized anastomotic leaks.
Authors queried a large dataset managed by the U.S. Veterans Affairs program, including 39,175 patients (95% men) who underwent colon resection between 2004 and 2023.
They found 1,227 (3%) who experienced a postoperative organ space surgical site infection (OSSI), the most closely corresponding diagnosis to anastomotic leak. They then bifurcated these cases according to whether the OSSI diagnosis (infection) was recognized before or after a sepsis diagnosis.
This was a heuristic for whether the infection was identified early (before onset of sepsis, in 69%) or late (after a sepsis diagnosis, in 31%).
Unsurprisingly, patients whose postoperative infections were identified late (after a sepsis diagnosis) had worse outcomes:
Death within 30 days (2.2% vs. 7.8%, P<.001)
Greater need for reoperation (62% vs 40%, P<.001)
Longer lengths of stay (23 vs 18 days, P<.001)
These findings were robust to excluding other causes of sepsis (pneumonia, etc).
Most (91%) were nonemergent colon resections, and the findings were also robust to the indication for surgery (i.e., they were not driven by emergent repairs of bowel perforations).
Preventing and Identifying Anastomotic Leaks (and other postop infections after colorectal surgery)
“Low-FTR” centers (failure-to-rescue, meaning deaths after surgery) tend to adhere to enhanced recovery after surgery (ERAS) best practices.
Thus, the best prevention is to go work at one of these centers, as it’s not possible to initiate these operational and cultural changes without engaged surgeon leadership paired with effective communication and collaboration with critical care teams, all backed by strong institutional support.
While unstandardized, these protocols usually include preadmission measures (nutrition, etc), as well as postoperative interventions:
Closed ICUs (intensivist-run and well-staffed)
Bundles to prevent surgical site infections
Effective pain management
Preemptive, multimodal antiemetic prophylaxis
Goal-directed fluid therapy (avoiding overload or depletion), sometimes with hemodynamic monitoring
Stopping maintenance fluids asap postoperatively
Proactive use of vasopressors when needed to maintain MAP >65 mmHg, for hypotension persisting after adequate volume resuscitation
While such studies are subject to confounding, high adherence with ERAS best practices has been strongly associated with lower mortality after colorectal surgery.
Diagnosing Anastomotic Leaks
Anastomotic leaks are easy to miss or “wish away” by attributing their symptoms and signs to one of the many causes they can masquerade as.
Tachycardia, oliguria, tachypnea, and general failure to “rally”—persistent absent bowel function or low-grade encephalopathy—these common signs of anastomotic leak are nonspecific and may be subtle.
Persistent fever and diffuse abdominal pain are more specific signals that should generate a high degree of suspicion for a leak.
Procalcitonin and C-reactive protein have been studied as biomarkers. Their performance characteristics remain unclear, but low CRP levels indexed to postop day may help rule out leaks. Leukocytosis is often absent until late.
Overt peritonitis or purulent or feculent drainage from surgical drains are late findings that may portend a worse outcome.
CT abdomen and pelvis with IV and rectal contrast is the first-line test to diagnose anastomotic leak.
Extraluminal air, fluid collections near the anastomosis, or extravasation of rectal contrast are suggestive or diagnostic.
Water-soluble enemas (Gastrografin) can make the diagnosis but are less sensitive than CT.
For low pelvic anastomoses, flexible sigmoidoscopy can allow visualization of the staple line directly.
Not All Anastomotic Leaks Require Surgery
Some leaks (Grade A) are asymptomatic, discovered incidentally on imaging, and resolve with observation alone.
Grade B leaks can be managed nonsurgically with antibiotics and percutaneous abscess drainage.
Leaks producing systemic sepsis (Grade C) require reoperation (laparotomy and washout with creation of a diversion ostomy), although minimally invasive endoscopic therapies are in use at some centers.
References
Savitch SL, Lagisetty KH, Suwanabol PA. Delayed Diagnosis of Anastomotic Leak and Failure to Rescue After Colon Resection. JAMA Surgery. Published online February 11, 2026. doi:https://doi.org/10.1001/jamasurg.2025.6551
Anastomotic Leakage in Colorectal Cancer Surgery. Surgical Oncology. 2022. Chiarello MM, Fransvea P, Cariati M, et al.
Management of Low Colorectal/Coloanal Anastomotic Leak: Results of a French National Intergroups Practice Survey (FRENCH-GRECCAR-SFCD). World Journal of Surgery. 2025. Pastier C, Ben Hmida W, Lefèvre JH, et al.
Considerations in Case of Suspected Anastomotic Leakage in the Lower GI Tract. Best Practice & Research. Clinical Gastroenterology. 2024. de Wit A, Daams F.
Management of Anastomotic Leak: Lessons Learned From a Large Colon and Rectal Surgery Training Program. World Journal of Surgery. 2014. Blumetti J, Chaudhry V, Cintron JR, et al.