Retroperitoneal fibrosis

The disease may be primary, idiopathic (Ormonds disease) or secondary to malignancy (especially lymphoma and metastatic colon cancer or breast cancer), medication (especially methlysergide, used in the treatment of migraine), adjacent inflammatory processes, retroperitoneal fluid collections (including blood, urine or contrast media) and inflammatory aortic aneurysms. At least 70% of cases are idiopathic. Primary retroperitoneal fibrosis may affect any age, but the usual age of onset is 30-60 years. The male : female ratio is 3:1. Approximately 15% of patients have additional fibrotic processes outside the retroperitoneum, including mediastinal fibrosis, fibrosing thyroiditis, sclerosing cholangitis, and fibrotic orbital pseudotumours.

Symptoms are nonspecific and include malaise, anorexia, weight loss and low back or flank pain. Uraemia, deep venous thrombosis or claudication may develop due to ureteric, venous or arterial compromise, respectively. Intravenous urography shows medially deviated and narrowed ureters, with proximal dilatation (Fig.1). The findings may be unilateral or bilateral, and the length of the narrowed segments and degree of pelvicaliectasis are both variable. Any portion of the ureter may be involved, but the middle third is most typical. Fluoroscopy, if performed, shows the affected segment to be aperistaltic. Retrograde pyelography may be required to demonstrate the findings when poor renal function is present, and typically there is little resistance to the retrograde passage of the catheter. On ultrasound, retroperitoneal fibrosis appears as clearly marginated and markedly hypoechoic retroperitoneal infiltrative masses. At CT, a sharply marginated homogeneous soft tissue mass encases the ureters, intravenous urography and aorta, and may enhance after intravenous contrast media (Fig.2). Retroperitoneal fibrosis does not extend posterior to the great vessels. Obstruction of the inferior vena cava has been reported.

MRI also shows the retroperitoneal mass, which is of intermediate T1 signal intensity. Benign long-standing retroperitoneal fibrosis is typically of low T2 signal intensity, due to dense fibrosis. High T2 signal intensity may be due to more acute active disease or retroperitoneal fibrosis secondary to malignancy. While the imaging findings are usually relatively characteristic, biopsy is often required to confirm the diagnosis and exclude underlying malignancy. Medical treatment with corticosteroids may be attempted in milder cases, based on the belief of some authorities that retroperitoneal fibrosis is an immunological process. However, surgical ureterolysis is usually the definitive treatment. The ureter is dissected free from the fibrous plaque, and placed intraperitoneally or wrapped in omentum to prevent recurrence.

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