Pictorial review: radiological diagnosis of anastomotic leakage with water-soluble contrast enema after anterior resection of the rectum.

For patients who have undergone colorectal surgery, anastomotic leakage is a serious and challenging complication with a variable rate ranging between 1.8% and 19.2%. Postoperative anastomotic leaks after colorectal surgery can have severe consequences for patients, particularly ones who present with few or no symptoms. Computed tomography and/or water-soluble contrast enema (WSE) are the most frequently utilized imaging methods to identify and diagnose anastomotic leaks early. WSE is a safe and complication-free procedure that allows to identify the presence of otherwise unrecognized anastomotic leaks, both in asymptomatic and symptomatic patients. Fluoroscopic rectal examination using a water-soluble contrast agent for postoperative patients is never an easy examination to perform since it requires careful preparation, skill, and knowledge. Four morphological types of anastomotic dispersion have been described: "saccular type", "horny type", "serpentine type" and "dendritic type". Among 4 types of leakage, dendritic and serpentine types are more frequently followed by clinical symptoms and none of the dendritic type resolves spontaneously. On the other hand, the saccular and horny types have a better prognosis after healing of the loss and subsequent restoration of the ostomy as they consist of a cavity that provides a sort of physical barrier to the spread of inflammation. The aim of this pictorial essay was to illustrate the spectrum of imaging findings of morphological types of radiologic leakages on WCE in patients with colorectal surgical anastomosis. We have also tried to provide tips and tools to enable identification of radiological leakages on retrograde WCE, particularly of the smallest leaks which can be more easily missed.