Supplementary Material for: Rectal adenocarcinoma presenting as a perirectal abscess

Classic symptoms of rectal cancer (RC) such as hematochezia, tenesmus, rectal pain, and bowel habit changes are well known but can be non-specific and misdiagnosed. Rare presentations, in combination with these conventional symptoms, can occur warranting a higher degree of clinical suspicion. Here we report a case of rectal adenocarcinoma presenting as a perirectal abscess. A 52-year-old male with uncontrolled diabetes mellitus presented with a two-year and two-month history of rectal bleeding and changes in bowel habits, respectively, which were attributed to other conditions. He initially presented with left buttock pain and severe sepsis. Subsequent workup for suspected Fournier’s gangrene and perirectal abscess led to the discovery of a rectal adenocarcinoma (pT4N0M0, stage IIB/C). A combination of debridement, antibiotic therapy, neoadjuvant chemoradiation, and abdominoperineal resection resulted in improvement of the patient’s condition and remission. In conclusion, rare presentations of RC, such as a perirectal abscess, especially if present in conjunction with conventional RC symptomology, may necessitate the workup of RC.