What is retroperitoneal adenopathy?

It's the swelling of the lymph nodes located outside or behind one of the the peritoneums. The parietal peritoneum is the portion that lines the abdominal and pelvic cavities. The visceral peritoneum covers the external surfaces of most abdominal organs, including the intestinal tract. Therefore, it's the swelling of the lymph nodes located around the abdominal area.