Delayed anastomotic leakage after short-course radiotherapy in a 91-year-old patient with rectal cancer.

Delayed anastomotic leakage (DAL), defined as occurring > 30 days postoperatively, poses diagnostic and therapeutic challenging. Radiotherapy is a recognized risk factor for DAL, but most studies focused on conventional radiotherapy rather than short-course radiotherapy (SCRT). We describe a case of DAL following SCRT in a very elderly patient to emphasize late presentation and diagnostic considerations. A 91-year-old man with rectal cancer underwent preoperative SCRT (25 Gy/5 fractions) without chemotherapy because of advanced age and low performance status. Twelve weeks later, he underwent robot-assisted low anterior resection with diverting ileostomy. Seventeen months postoperatively, he presented with general malaise and hematochezia. C-reactive protein was elevated to a higher level than postoperative, and colonoscopy identified an anastomotic posterior fistula, leading to DAL diagnosis. Transverse colostomy was subsequently performed, after which he remains asymptomatic, and C-reactive protein levels has returned to initial postoperative levels. This case highlights DAL occurring 17 months after low anterior resection with SRCT alone in a nonagenarian. DAL should be considered a potential late complication following both conventional radiotherapy and SCRT. Careful monitoring of C-reactive protein may provide a valuable diagnostic trigger for earlier detection, particularly in posterior site leakage where symptoms may be subtle or delayed.