RETROPERITONEAL FIBROSIS

Retroperitoneal fibrosis (RPF) was first clearly described by the French urologist, Albarran, at the beginning of the 20th century.
Benign causes
- Idiopathic RPF comprises two thirds of benign cases. A fibrous plaque extends laterally and downwards from the renal arteries encasing the aorta, inferior vena cava, and ureters, but rarely extends into the pelvis. The central portion of the plaque consists of woody scar tissue, while the growing margins have the histological appearance of chronic inflammation. It may be associated with mediastinal, mesenteric, or bile-duct fibrosis.
- Drugs including methysergide, betablockers, haloperidol, amphetamines, and LSD.
- Chronic urinary infections including TB and syphilis.
- Inflammatory conditions such as Crohn's disease or sarcoidosis.
- Abdominal aortic aneurysm (AAA), intra-arterial stents, and angioplasty may induce idiopathic fibrosis due to peri-aortitis, haemorrhage, or an immune response to insoluble lipoprotein.

Malignant causes
- Lymphoma is the most common cause; also sarcoma.
- Metastatic or locally infiltratative carcinoma of the breast, stomach, pancreas, colon, bladder, prostate and carcinoid tumours.
- Radiotherapy may cause RPF, although rare today with precise field localization.
- Chemotherapy, especially following treatment of metastatic testicular tumours, may leave fibrous masses encasing the ureters. These may or may not contain residual tumour.

Presentation
- Idiopathic RPF classically occurs in the 5th or 6th decade of life.
- Men are affected twice as commonly as women.
- In the early stage, symptoms are relatively non-specific, including loss of appetite and weight, low-grade fever, sweating, and malaise. Lower limb swelling may develop. Dull, non-colicky abdominal or back pain is described in up to 90% of patients.
- Later, the major complication of the disease develops: bilateral ureteric obstruction causing anuria and renal failure.
- Examination may reveal hypertension in up to 60% of patients and an underlying cause such as an AAA.

Investigations
- Inflammatory serum markers are elevated in idiopathic RPF (60 - 90% elevated ESR).
- Pyuria or bacteriuria are common.
- Ultrasound will demonstrate uni- or bilateral hydronephrosis.
- CT, IVU, or ureterography reveal tapering medial displacement of the ureters with proximal dilatation and will exclude calculus disease. Up to one third of patients will have a non-functioning kidney at the time of presentation due to longstanding obstruction.
- CT-guided fine needle or laparoscopic biopsy of the mass may confirm the presence of malignant disease, but a negative result does not exclude malignancy.

Management
- Emergency management of a patient presenting with established renal failure requires relief of the obstruction by percutaneous nephrostomy or ureteric stenting.
- Replacement of fluid and electrolyte losses following relief of bilateral ureteric obstruction is vital due to the frequent post-obstructive diuresis.
- Assess with daily weighing and measurement of blood pressure lying and standing.
- Steroids may decrease the oedema often associated with RPF and in this way help reduce the obstruction. If used, they are usually discontinued when inflammatory markers return to normal. The anti-oestrogen tamoxifen and cyclophosphamide have been used successfully in some patients.
- Surgical ureterolysis with omental wrap is often necessary to free and insulate the ureters from the encasing fibrous tissue.
- Biopsies are taken to exclude malignancy.
- Monitor for recurrent disease with serum creatinine and ultrasound 3 - 6 monthly for 5 years.