This study reports a case of pyoderma gangrenosum arising at a drainage orifice after a colostomy for cancer. The initial clinical presentation suggested intra-abdominal sepsis but the clinical assessment did not fit with laboratory findings or the CT scan. Forty hours later, the patient developed a reddish-purple ulcer at the drainage orifice. A diagnosis of pyoderma gangrenosum was made and systemic corticosteroid therapy was started. A dramatic response occurred over the next two days, obviating the need for surgical re-intervention. Pyoderma gangrenosum is an ulcerating necrotizing skin disorder of unknown etiology. It usually arises in association with underlying disease (mainly inflammatory bowel disease) and often occurs in para-stomal sites. Pyoderma gangrenosum arising at surgical sites is often mistaken for a postoperative infection and treated inappropriately with debridement and reopening of the wound which only exacerbates the pathology. Pyoderma gangrenosum is effectively treated with systemic corticosteroids.