Inflammation that affects your retroperitoneal space is a serious medical condition. It has a high mortality rate. However, early diagnosis and treatment can improve your outlook. The retroperitoneal space is the space between your peritoneum and your posterior abdominal wall. In less complicated terms, itâs the space in your abdomen behind the abdominal lining. It houses several major organs, including: kidneys. bladder. abdominal aorta. adrenal glands.