Idiopathic retroperitoneal fibrosis is an inflammatory condition characterised by the formation of tough fibrous tissue (fibrosis) on the tissues and organs behind the peritoneum — the membrane that lines the abdominal cavity. The word ‘idiopathic’ means of unknown cause.
‘Retroperitoneal’ structures include some of the muscles of the back, the aorta and inferior vena cava (large blood vessels taking blood from and to the heart), and the kidneys and ureters (tubes draining urine from the kidneys to the bladder). In severe cases of retroperitoneal fibrosis, one or both ureters may become blocked. This can lead to kidney failure.
Although the exact cause is unknown, doctors suspect that an autoimmune response — in which the body attacks its own tissue — may be involved. It is thought that the immune system attacks fatty material that leaks from the aorta when atherosclerosis occurs. Atherosclerosis is the build up of fatty deposits in the inner wall of an artery. This explains why the condition is sometimes called periaortitis, meaning inflammation around the aorta.
Some people with idiopathic retroperitoneal fibrosis also have other autoimmune conditions such as ankylosing spondylitis or systemic lupus erythematosus (SLE). Approximately 10 per cent of people with idiopathic retroperitoneal fibrosis have invasion of fibrous tissue elsewhere in the body, for example the thyroid gland or the tissue around the eyes.
Who is affected by idiopathic retroperitoneal fibrosis?
Idiopathic retroperitoneal fibrosis is rare: fewer than one in 200,000 people are affected. It is most common in people aged 40–60, and men are affected 2 to 3 times more often than women.
The main symptom is dull pain in the back, flanks, groin or abdomen. Occasionally there is also pain in the legs on walking.
People with idiopathic retroperitoneal fibrosis may develop leg swelling, weight loss, loss of appetite and nausea and vomiting, and they may feel generally ‘off colour’ — some of these symptoms can indicate kidney failure. Other symptoms of kidney failure are drowsiness and passing more or less urine than normal.
People with idiopathic retroperitoneal fibrosis often develop high blood pressure; however, this does not generally cause symptoms and is often only noticed at a medical check-up.
Occasionally, the fibrosis can cause problems with the bowel or the spinal cord, or clotting of blood in the veins.
Diagnosis of idiopathic retroperitoneal fibrosis
Blood tests often show signs of inflammation and anaemia (too few red blood cells or not enough haemoglobin — the molecule that carries oxygen to the tissues). Blood tests may also show kidney failure if the fibrosis is advanced.
CT (computerised tomography) or MRI (magnetic resonance imaging) scans of the abdomen should reveal the fibrosis and how far it has spread. Occasionally the condition is picked up incidentally when doctors do a CT or MRI scan to investigate an unrelated problem.
Retroperitoneal fibrosis can be secondary to injury, infection, cancer, enlargement of the aorta (aneurysm), and certain medicines. To rule out these causes and confirm that the fibrosis is idiopathic, your doctor may refer you for a biopsy. In this procedure tiny pieces of tissue from the back wall of the abdomen are collected for examination. This can be done under CT guidance or through surgery — either laparoscopic (keyhole) surgery or an open operation.
Your doctor may also want to investigate your urinary tract to see if the fibrosis has affected it. This can be done with an ultrasound or with a special X-ray of the kidneys and ureters called an intravenous pyelogram (IVP).
Treatment depends on how advanced the disease is. Surgery may be needed to free the ureters from the fibrosis; at the same operation the ureters can also be moved away from the fibrosis and protected by wrapping them in a portion of membrane taken from elsewhere in the abdomen. If the ureters are blocked, stents (drainage tubes) can be inserted so that the urine flows unobstructed into the bladder.
Various medicines can be used to suppress the fibrosis. These include steroids and medicines that suppress the immune response such as azathioprine (e.g. Imuran), methotrexate (e.g. Methoblastin) and cyclophosphamide (Cycloblastin, Endoxan).
Kidney failure usually improves with treatment; however, dialysis may be needed if kidney function does not improve.
The outlook for people with idiopathic retroperitoneal fibrosis depends on the extent of the fibrosis and the amount of damage to the kidneys.
Generally, idiopathic retroperitoneal fibrosis in itself does not shorten a person’s life. However, fibrosis that develops as a reaction to severe atherosclerosis is another story — atherosclerosis has many health consequences including coronary heart disease, which can cause a heart attack. So if you are diagnosed with atherosclerosis, you should ask your doctor about what can be done to reduce your risk of cardiovascular disease and its complications.
Fibrosis can recur (come back) after treatment and this may not cause symptoms. If you have been treated for idiopathic retroperitoneal fibrosis, you should attend regular follow-up appointments with your doctor so that the disease can be detected if it recurs.