Retroperitoneal fibrosis: Year of the Zebra

Retroperitoneal fibrosis is a chronic inflammatory disorder where fibrous, scar-like tissue develops in the retroperitoneal area. The peritoneum is the serous membrane that lines the abdominal cavity and covers the abdominal organs. The growth of fibrous tissue in the retroperitoneal space, or the space behind the peritoneum, leads to compression of the structures in that area, such as blood vessels like the inferior vena cava, and the ureters, which are the fibromuscular tubes that carry urine from the kidneys into the urinary bladder. 

Initially, retroperitoneal fibrosis may be asymptomatic or cause nonspecific symptoms, like lack of energy, loss of appetite, unexplained weight loss, and low-grade fever. 

As the disease progresses, the most common symptom is dull, low back or flank pain. In some cases, a palpable mass may be found in the abdomen or rectum. External compression of the ureters may obstruct the normal flow of urine, resulting in the back-up of urine into the kidneys, which can result in kidney damage over time. Compression of the inferior vena cava may result in swelling of the lower limbs and deep vein thrombosis, whereas compression of the retroperitoneal gonad vessels may lead to testicular pain and swelling.