Background <p>Pelvic radiotherapy plays a key role in the treatment of rectal cancer, often used in combination with surgery and chemotherapy. However, it is associated with delayed complications, such as enteric fistulas, but present diagnostic and therapeutic challenge. Case presentation. This report describes a case of a post-radiation enteric fistula identified via diagnostic imaging in a patient who had undergone total proctectomy with a permanent colostomy. The uniqueness of this case lies in the enteric fistula feeding a presacral collection, thus mimicking a coloanal anastomosis.</p> Conclusions <p>This case highlights the importance of considering radiation-induced enteric fistulas as a potential diagnosis in patients presenting with pelvic collections after radiotherapy. Early diagnosis, enabled by advanced imaging techniques such as c<i>omputed tomography</i> or <i>magnetic resonance imaging</i>, is crucial for appropriate management. Multidisciplinary collaboration is essential to improve clinical outcomes and address these rare but serious complications.</p>