Description of the case of a patient who goes to the emergency service of one General Hospital Zone of the Instituto Mexicano del Seguro Social, I.M.S.S. with a left abdominal-inguinal pain and fever of one month of evolution. The study of the case, gets tomographic evidence of a left psoas abscess of large dimensions is obtained with laboratory tests compatible with systemic inflammatory response. Percutaneous drainage was performed in the emergency service to continue his hospital stay later, with gradual improvement until his discharge. Few cases are reported of this pathology and much less of those that can be resolved in this way so little invasive.