Hernia is described as the protrusion of an organ into the wall of its normal containing cavity. Internal hernia (IH) involves protrusion of viscera through: a peritoneal or mesentery defect, a normal or abnormal compartment of the peritoneal cavity. Hernias occurring in the pelvis cavity are usually classified according to the fascial margins breached and include sciatic, obturator and those through the rectouterin pouch: elytrocele and enterocele. Those hernias are defined by the protrusion of a viscus through the wall of the pelvis due to weakness of the pelvic fascia and/or muscles. Pelvic hernia through the pouch of Douglas (PD) involves the genital tract in female (elytrocele and enterocele). Sometimes described in the literature as Douglas hernia, this type of hernia must be distinguished from the conventional IH. As defined before, the borders to be considered for IH is the peritoneal membrane, which is not a real solid wall but delimitates the peritoneal cavity; and there is no peritoneal defect in elytrocele or enterocele. A PubMed search for IH through a defect in the peritoneal PD revealed only five female cases, making this an extremely rare condition. To our knowledge, we have presented here the only published case in a male. This probably congenital and morphologic anomaly (defect) of pouch of Sir Douglas must be distinguished as the real "Douglas IH". Authors discuss the concept of a new and more detailed classification of IH.