Retroperitoneal Fibrosis (Peri-aortitis)

Retroperitoneal fibrosis encompasses a range of diseases characterised by the presence of a fibro-inflammatory tissue, which usually surrounds the abdominal aorta and the iliac arteries and extends into the retroperitoneum to envelop neighbouring structures, e.g. the ureters.¹

• Retroperitoneal fibrosis is thought to be an autoimmune response to an insoluble lipid that has leaked through a thinned arterial wall from atheromatous plaques.
• Fibrous tissue covers the retroperitoneal structures such as the aorta, vena cava, ureters and psoas muscle. It may extend from the renal pedicle to below the pelvic brim.
• The centre of the plaque is usually located at the level of the aortic bifurcation. The fibrous tissue may bifurcate and follow the common iliac arteries.

• Relatively uncommon, with an incidence of 1 case per 200,000 population.²
• Overall 3 times more common in males than in females but this varies with cause, e.g. methysergide-related retroperitoneal fibrosis is more common in females.
• Can affect any age but the peak age of presentation is between 40-60 years.

• In approximately 70% of patients, no underlying cause is found (idiopathic retroperitoneal fibrosis)
• Drugs: e.g. methysergide, beta-blockers, methyldopa, amphetamines, phenacetin, pergolide and cocaine
• Abdominal aortic aneurysm
• Trauma to the renal tract
• Infection
• Retroperitoneal malignancy
• Post-irradiation therapy or chemotherapy

Retroperitoneal fibrosis may be associated with primary biliary cirrhosis, fibrosing mediastinitis, panhypopituitarism, glomerulonephritis, rheumatoid arthritis, systemic lupus erythematosus, polyarteritis nodosa, ankylosing spondylitis or Hashimoto thyroiditis, supporting the hypothesis of an immune-mediated mechanism.

• Most patients present with non-specific symptoms of less than 12-months' duration.
• Patients may present with the complications of retroperitoneal fibrosis (see Complications section below).
• Early clinical features depend on any underlying cause.
• Advanced disease causes obstructive uropathy and renal failure. The patient may present with acute renal failure or chronic renal failure resulting from ureteric involvement.
• The most common presentation is pain, which may occur in the loin, back, scrotum or the lower abdomen.
• Fever, weight loss, nausea and vomiting, malaise.
• Polyuria, polydipsia, anorexia, nocturia, oliguria, urinary frequency and haematuria.
• Children may present with hip or gluteal pain.²

• Other conditions that can cause ureteric obstruction and renal failure, e.g retroperitoneal abscess, periaortic haematoma, pelvic surgery, radiation therapy and amyloidosis.
• Similar radiological appearances may be caused by abdominal aortic aneurysm, lymphomas, sarcomas, pancreatic carcinomas and metastatic malignancies.

• Blood and urine tests: findings may include renal dysfunction, anaemia, raised ESR, raised white cell count and pyuria.
• Plain x-ray: non-specific but may show evidence of complications, e.g. bowel obstruction, pulmonary oedema (renal failure).
• Ultrasound: may help in identifying the retroperitoneal mass; can demonstrate degree of obstruction to the ureters and kidneys.
• Barium follow-through and enema: bowel obstruction.
• Intravenous urography: shows dilated ureters with medial deviation of ureters. IVU may lead to contrast nephropathy; therefore good hydration is essential and IVU should be used with caution in the elderly and those with renal impairment (always check renal function beforehand).
• Retrograde pyelography: for patients with severely impaired renal function.
• Aortography, venography, and lymphangiography help in assessing the level and extent of occlusion.
• CT and MRI: delineation of the extent of the masses of retroperitoneal fibrosis.
• Isotope renography is useful in the serial assessment of renal function.²
• Biopsy under CT guidance: differentiate benign masses from malignant retroperitoneal masses; biopsy in retroperitoneal fibrosis shows periaortic inflammation with lymphocyte and plasma cell infiltrate.
• The diagnosis may not be established until surgical exploration.

• In drug-related retroperitoneal fibrosis, stopping the offending drug may result in resolution of urinary tract obstruction and symptoms.
• The use of steroids in retroperitoneal fibrosis remains controversial but has been used successfully as an adjuvant to surgical ureterolysis.³
• Immunosuppressive drugs, e.g. azathioprine, cyclophosphamide and tamoxifen, have been used.
• Drainage of the upper urinary tract can be performed as a temporary measure. Percutaneous nephrostomy helps restore renal function, fluid, electrolyte and acid-base balance prior to surgery.
• Open or laparoscopic ureterolysis and/or prednisolone is used to relieve obstruction. Placement of ureteric stent(s) has the advantage of avoiding risks associated with surgery but may not offer complete relief and stents may need replacing if steroid therapy is unsuccessful.⁴
• Surgery may be required to resolve urinary tract obstruction or obstruction of other structures.

• Hypertension is common.
• Fibrosis may cause compression of the major arteries, veins and lymphatics, resulting in thrombophlebitis, arterial insufficiency and lower limb oedema.
• Obstruction of the duodenum and colon may cause bowel obstruction.
• Obstruction of the common bile duct may cause jaundice.
• Spinal involvement may cause neurological abnormalities in the lower limbs.

• Prognosis depends on the degree of renal impairment at presentation and the degree of obstruction of the urinary tract, bowel and blood vessels.²
• Idiopathic (non-malignant) retroperitoneal fibrosis has a generally good prognosis unless not appropriately diagnosed or treated, when the disease can cause severe complications, e.g. end-stage renal failure.¹
• Malignant retroperitoneal fibrosis has a poor prognosis. Most patients only live for 3-6 months after receiving a diagnosis of malignant retroperitoneal fibrosis.²
• Close life-long follow-up is required for possible progressive or recurrent disease.³