Peritonitis is an acute inflammation of the peritoneal cavity, most often secondary to the perforation of a digestive organ and/or the diffusion of an intra-abdominal septic focus. It constitutes a medical and surgical emergency that can rapidly engage the vital prognosis due to its physiopathological consequences. The Mannheim Peritonitis Index (MPI) is an independent, objective and effective scoring system for predicting mortality and has advantages over other scoring systems; it is easily used and reproducible with good sensitivity and specificity.