Endoscopic incision and debridement for presumed delayed postoperative anastomotic submucosal abscess of the rectum: a case report.

backgroundAnastomotic lesions after colorectal cancer surgery are uncommon and usually signify tumor recurrence or early complications. Delayed submucosal abscess occurring several years after curative resection is extremely rare. Due to the lack of specific clinical manifestations, imaging studies may mimic tumors or other subepithelial lesions, making the diagnosis challenging. Moreover, such lesions are located deep within the intestinal wall at the anastomotic site, which further complicates their management. Herein, we report a rare case of presumed delayed postoperative anastomotic submucosal abscess of the rectum successfully treated by endoscopic incision and debridement, highlighting diagnostic pitfalls and therapeutic feasibility. CASE DESCRIPTION: A 43-year-old woman presented with an incidentally discovered submucosal mass at the rectal anastomotic site during routine surveillance colonoscopy, eight years following laparoscopic low anterior resection for rectal cancer. She was completely asymptomatic (no abdominal pain or distension) with unremarkable laboratory findings, including normal tumor markers. Endoscopic ultrasound (EUS) revealed a slightly hyperechoic solid lesion originating from the submucosa, measuring approximately 1.61 cm × 0.81 cm, with relatively clear borders and heterogeneous internal echoes. Given the diagnostic uncertainty and the lesion's deep intramural location, endoscopic treatment was undertaken for both diagnostic and therapeutic purposes. The procedure involved a longitudinal incision through the muscularis propria at the central part of the lesion elevation, which unexpectedly revealed a sinus cavity containing purulent fluid and yellow plaque-like solid material, suggesting the presence of a chronic abscess. The cavity was irrigated, and the defect was closed with clips. Post-procedure EUS confirmed complete resolution of the mass, and the patient recovered uneventfully without complications.

conclusionsThis case shows that a presumed delayed anastomotic submucosal abscess, although rare, should be considered in the differential diagnosis of mass-like lesions occurring years after rectal cancer surgery. However, in the absence of microbiological and pathological confirmation, the exact nature of the lesion remains uncertain. Alternative explanations, including a chronic postoperative cavity, anastomotic sinus formation, implantation cyst, or other benign postoperative changes, cannot be completely excluded. Nevertheless, endoscopic incision and debridement may represent a safe, minimally invasive diagnostic and therapeutic option in selected cases of presumed postoperative abscess.