Retroperitoneal fibrosis is a disorder in which inflammation and extensive scar tissue (fibrosis) occur in the back of the abdominal cavity, behind (retro-) the membrane that surrounds the organs of the digestive system (the peritoneum). This area is known as the retroperitoneal space. Retroperitoneal fibrosis can occur at any age but appears most frequently between the ages of 40 and 60.

The inflamed tissue characteristic of retroperitoneal fibrosis typically causes gradually increasing pain in the lower abdomen, back, or side. Other symptoms arise from blockage of blood flow to and from various parts of the lower body, due to the development of scar tissue around blood vessels. The fibrosis usually develops first around the aorta, which is the large blood vessel that distributes blood from the heart to the rest of the body. Additional blood vessels including the inferior vena cava, which returns blood from the lower part of the body to the heart, may also be involved. Obstruction of blood flow to and from the legs can result in pain, changes in color, and swelling in these limbs. Impairment of blood flow in the intestines may lead to death (necrosis) of intestinal tissue, severe pain, and excessive bleeding (hemorrhage). In men, reduced blood flow back toward the heart (venous flow) may cause swelling of the scrotum.

Because the kidneys are located in the retroperitoneal space, retroperitoneal fibrosis may result in blockage of the ureters, which are tubes that carry urine from each kidney to the bladder. Such blockages can lead to decreased or absent urine flow and kidney failure. When the kidneys fail, toxic substances build up in the blood and tissues, leading to nausea, vomiting, weight loss, itching, a low number of red blood cells (anemia), and changes in brain function.

• Asbestos exposure
• Smoking
• Neoplasms (tumor)
• Infections
• Trauma
• Radiotherapy
• Surgery
• Use of certain drugs (including those that contain methysergide, a medication sometimes used to treat migraines)

Most cases of retroperitoneal fibrosis are sporadic, which means that they occur in people with no apparent history of the disorder in their family. In rare cases, the condition has been reported to occur in a few members of the same family, but the inheritance pattern is unknown.

• Dull pain in the abdomen, back, or side that increases with time
• Decreased circulation in the legs leading to pain, swelling, and discoloration
• Impaired blood flow to the intestines leading to death (necrosis) of intestinal tissue, severe pain, and excessive bleeding (Hemorrhage)
• Swelling of the scrotum in men

• Decreased urine output
• Total lack of urine (anuria)
• Nausea, vomiting, weight loss, itching, anemia, and changes in thinking caused by kidney failure and the resulting build-up of toxic chemicals in the blood.

The outlook for patients with retroperitoneal fibrosis is usually considered to be good. Renal recovery frequently is observed within the first 2 weeks, but patients should always be checked periodically since disease recurrence has been reported up to 10 years after finishing the treatment. Obstruction of the ureter may recur in up to half of patients who had surgery alone and in about 10% of those treated with both surgery and medication. Severe complications such as chronic renal failure, requiring kidney transplant, can arise in rare cases. Other, less frequent complications, may include:

• Hypertension
• Scrotal swelling
• Inferior vena cava thrombosis

Retroperitoneal fibrosis occurs in 1 in 200,000 to 500,000 people per year. The disorder occurs approximately twice as often in men as it does in women, but the reason for this difference is unclear.