EP369 - An unusual case of a colorectal anastomotic dehiscence presenting three decades after the index operation

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Purpose/Background: Colorectal anastomosis is performed for many indications. One of the most concerning complications of these anastomoses is a leak. There are several risk factors associated with leakage including such as male sex, obesity, nutritional status, technical factors, neoadjuvant and adjuvant therapy, and gut microbiome among others (1). Leaks are often divided into early and late leaks with a cutoff between the two anywhere between 7 and 30 days (2). We report a case of colorectal anastomotic dehiscence that occurred almost thirty years following a low anterior resection.

Methods/Interventions: The patient is a healthy 84-year-old man who was found to have rectal adenocarcinoma in 1996. He underwent neoadjuvant chemoradiation followed by a low anterior resection with primary anastomosis. He did not require adjuvant therapy. He was compliant with postoperative surveillance, including a complete colonoscopy as recently as 2019 that was normal. In December 2023, he contracted COVID infection and following this, he had progressive weight loss, fatigue and pelvic pain. He was taking antihypertensive but not on any immunosuppressive medications. A CT scan of abdomen and pelvis (Feb 2024) demonstrated 6x4 cm fluid collection adjacent to his prior anastomosis and sacral osteomyelitis (Fig 1). He underwent endoscopy which showed approximately 50% anastomotic dehiscence with a large granulating cavity in the presacral space (Fig 2 (a) and (b)). In May 2024, resection of the anastomosis was attempted, but dense adhesions in the pelvis rendered further dissection unsafe, leading to the decision to perform an end descending colostomy instead.

Results/Outcomes: The patient recovered well from the diversion, with gradual improvement in the sacral osteomyelitis and presacral abscess following an extended course of antibiotics. However, in August 2024, he developed a partial small bowel obstruction that eventually required laparotomy, adhesiolysis, small-bowel resection and repair of cystotomy. Pathology revealed calcified necrotic debris in the bladder and small bowel. With his age and extensive adhesions, fecal diversion will be permanent. He is otherwise recovering well.

Conclusion/Discussion: Colorectal anastomosis has a known risk of leak with many contributing factors. Although opinions and data vary, late leaks are generally believed to be associated with factors that impair perfusion (3) and long-term wound healing. There are several reports of adjuvant Bevacizumab leading to leaks as far out as 886 days after the index operation (4). Our recent review of the literature did not identify any published data linking COVID with anastomotic complications. In this case we identified a leak nearly three decades after the index operation that did not have any of these clear risk factors other than neoadjuvant chemoradiation.