Diseases of the retroperitoneal space in the dog and cat

The retroperitoneal space (RPS) is an anatomical area bounded dorsally by the sublumbar musculature and ventrally by the peritoneal surface of the abdomen. The RPS communicates with the pelvic space and mediastinum and is subject to primary diseases of the RPS connective tissue and to extension of disease from organs lying within or adjacent to it. Primary diseases include retroperitonitis, pneumoretroperitoneum, non-neoplastic retroperitoneal space-occupying lesions, and primary neoplasms of the RPS. Primary diseases of kidneys, ureters, adrenal glands or retroperitoneal lymph nodes may extend into the RPS, and the RPS may be the site of metastatic neoplastic disease. Clinical signs suggestive of retroperitoneal disease include lumbar pain, pyrexia, lethargy, and signs referable to organs within the RPS