Anastomotic leaks after low anterior resection for rectal carcinoma: evaluation with CT and barium enema

After low anterior resection of rectal carcinoma, anastomotic leaks are common and may be clinically silent. Radiologic abnormalities related to this leakage may be confusing and may persist for years without symptoms. The purpose of this study was to evaluate the appearance of these leaks on barium enemas and CT scans and to determine their course over time.

During a 7-year period, we collected CT scans and barium enemas in 35 patients with anastomotic leaks after low anterior resection. A leak was documented by the presence of rectal contrast material in an extraluminal collection, endoscopic visualization of anastomotic breakdown, or persistence of presacral air longer than 6 months after surgery. Twenty patients had examinations in the immediate postoperative period and 25 patients had 42 studies in the long-term follow-up period (6 months to 10 years). The CT appearance was compared with that in 40 patients who did not have evidence of leaks after low anterior resection.

Abnormalities consisted of air-fluid collections in the presacral space, extraperitoneal tracking along the iliac vessels, and perirectal anterior extension. Collections tended to diminish, but some air and soft-tissue masses persisted for months or years (up to 10 years in one case). In 70% of patients without leaks, no soft-tissue abnormality was apparent in the presacral space. In both groups of patients, the presacral space was widened and the rectum was anteriorly located, more so in patients with leaks than in those without. Seven patients had recurrent tumor. In the late stages, bulky soft-tissue masses obliterated the residual air and soft-tissue abnormality due to the leak.

Radiologists should be aware of the spectrum of findings due to anastomotic leaks after low anterior resection and the persistence of presacral abnormalities. Delayed symptoms mimic those of recurrence, and radiologic findings may be confusing. On some CT scans, it may not be possible to tell the difference, but changes due solely to leaks must be included in the differential diagnosis.