Leakage at the anastomotic site is the most common complication of colonic resection in the early postoperative period, and the cause of the highest morbidity and mortality. The rate of leakage is highest with low anterior resection, with clinically significant leaks reported in 5 to 10% of cases.
CT imaging may also be useful in the evaluation of postoperative leaks. In addition to demonstration of extraluminal contrast, associated abscesses may be identified. Contrast medium and/or air in the rectum and in a collection posterior to it has been termed the “double-rectum” sign. More precise identification of the site of leakage is generally determined with a water-soluble enema than with CT imaging, however. The retrorectal space typically widens after anterior resection; however, undue widening may suggest an anastomotic leak. In one study, CT images showed the retrorectal space to be 2cm or more in patients without anastomotic leaks. The same authors reported that the retrorectal space was greater than 5 cm in 70% of cases with acute leaks. Presacral fluid can often be identified normally in the postoperative period and can be distinguished from a leak by the absence of contrast medium and/or air. In some cases, a collection may be the cause of anastomotic dehiscence rather than its result. The identification of air in the presacral space for longer than 6 months after surgery is also an indication of leak.
“radiology images of “Double-rectum” sign due to leak.” (A,B) CT scan through the inferior pelvis demonstrates fluid in the rectum and an abscess containing fluid and air posterior to the rectum.