Peritoneography and Herniography in Non-Human Primates

There have been infrequent reports of congenital and acquired hernias in the nonhuman primate (2, 4, 12, 13). Recently restraint systems have been designed for chronic studies and long-term experimentation. Many of these systems are of the type in which the animal is sitting upright in a chair or cart with cuff devices to limit the motion of the extremities (3, 7). We have noted that these methods of restraint have resulted in an increase of inguinal hernias in male primates utilized for chronic investigatory studies. Often the diagnosis of an inguinal hernia can be made by physical examination, but we have encountered small hernias that were not clinically detectable. In our experience, physical examination is often misleading when predicting whether or not an animal will develop a hernia on the opposite side. Because of this, many surgeons, in human practice, routinely explore the opposite groin at surgery because they, in past experience, found a patent processus vaginalis which was not apparent on pre-operative physical examination. In children, approximately 40% with clinical evidence of a unilateral inguinal hernia have a patent processus in the opposite groin. Of this group, about 20% will eventually develop a hernia into the contralateral open processus vaginalis (14). In 1967, it was suggested that positive contrast peritoneography (herniography) could be substituted for surgical exploration (1). This diagnostic procedure in our experience has proved to be an accurate method of recognizing the existence and configuration of patent vaginal processes, hydroceles, hernias, and also delineates a number of other intraperitoneal structures. For these reasons we utilized this diagnostic study in our non-human primate population, both to test its feasibility and to establish normal findings.