We present the case of a 75-year-old patient with moderate Alzheimer's disease who presented with abdominal pain of three days' duration, with fever. On examination she presented with diffuse abdominal pain and peritonism. A computerised tomography (CT) scan was requested, which revealed the presence of free fluid, pneumoperitoneum, with infiltration and thickening of the entire colon wall with the presence of calcified faeces inside. The location of the perforation was not visualised (image). The patient underwent urgent surgery and was found to have diffuse faecaloid peritonitis with a perforation at the level of the sigma. A Hartmann's operation was performed, with a left hemicolectomy due to the finding of a new perforation at the level of the splenic angle of the colon.

