Sacral osteomyelitis as a rare cause of anorectal pain several years following treatment for rectal carcinoma.

A 66-year-old man was treated for a moderately differentiated T3 N1 M0 adenocarcinoma of the rectum in 2015 with preoperative short course radiotherapy, anterior resection and then adjuvant chemotherapy with oxaliplatin and capecitabine. Following ileostomy reversal, he complained of intense, unremitting anorectal pain. After repeated scans, computed tomography (CT) showed findings suggestive of a longstanding anastomotic leak. Subsequent, magnetic resonance imaging (MRI) revealed osteomyelitis of the sacrum, with the development of sacral osteomyelitis in this context unusual. Our case highlights the importance of appropriate radiological imaging and that clinicians should consider osteomyelitis as a differential diagnosis in patients presenting with severe anorectal pain after treatment for rectal cancer.