A retrospective study of 135 consecutive postoperative water soluble contrast enemas has been performed to establish the safety of the technique and indications for its use. Normal and abnormal appearances at various levels of rectal anastomosis have been described. Postrectal fluid collections are associated with anastomotic dehiscence and may be a cause rather than effect. One low colorectal anastomosis was disrupted during administration of the enema; the procedure was otherwise safe and free from complication. The postoperative water soluble contrast enema is presented primarily as a research tool to define the true anastomotic leak rate, but may be useful in the diagnosis of a postrectal collection and to define the extent of an established leak.