Beware of false-negative CT scan for anastomotic leakage after colonic surgery

Background Anastomotic leakage is one of the most life-threatening complications after colonic surgery. Correct diagnosis and treatment is important to reduce morbidity and mortality. An abdominal CT scan is one of the main diagnostic tools in diagnosing anastomotic leaks. The aim of this study was to examine the accuracy of abdominal CT scanning to detect anastomotic leakage and to evaluate the consequences of a false-negative CT outcome. Methods All consecutive patients who underwent colonic resection for malignant disease between 2009 and 2011 or for benign disease in 2010 were reviewed. Patients in whom a postoperative abdominal CT scan was performed to detect anastomotic leakage were included. Results In 97 of 524 patients who underwent colonic surgery, an abdominal CT scan was performed for the suspicion of anastomotic leakage. Overall leakage rate was 10.9 % (n = 57). Mortality rate after leakage was 21.1 % (n = 12). Results from all abdominal CT scans revealed an overall sensitivity of 0.59 (95% CI 0.43-0.73), a specificity of 0.88 (95% CI 0.75-0.95), positive predictive value 0.82 (95 % CI 0.64-0.92), negative predictive value 0.70 (95 % CI 0.57-0.81), and an accuracy of 74 %. Delayed reintervention for anastomotic leakage due to a false-negative CT outcome resulted in death in 62.5 % (n = 5). Conclusion The sensitivity of abdominal CT scanning after colonic surgery is relatively low. A negative CT scan does not rule out anastomotic leakage. Even with a negative CT scan, we should remain equally alert at clinical deterioration as an argument for timely intervention.