Clinical History
A 57-year-old male patient with a history of diabetes, hypertension and dyslipedaemia. Blood chemistry, glucose 118, urea 149, Cr 8.96, BUN 69.6, Na 134. Is being studied for renal failure. The patient was prepared to perform CT with contrast (hydration and Acetylcysteine administration).
Imaging Findings
Non-contrasted abdominal CT shows a low-attenuation mass surrounding the infrarenal aorta and extending along the iliac artery and infrarenal aortic dilatation (Fig. 1 a-d). Abdominal angio-CT shows aneurysmal dilatation of the aorta, bilateral uretrohydronephrosis grade I/IV (Fig. 2 a-g). In the venous phase we see a slight contrast enhancement by the retroperitoneal mass and delayed nephrographic phase of both kidneys, both ureters are medialized (Fig. 3 a-f). The excretory phase (15 min) shows an absence of the right kidney excretion (Fig. 3 a-e).
Discussion
Non-neoplastic primary retroperitoneal solid masses include pseudotumoural lipomatosis, retroperitoneal fibrosis, Erdheim-Chester disease, and extramedullary haematopoiesis.
Retroperitoneal fibrosis is an uncommon collagen vascular disease of unknown cause that can mimic a retroperitoneal tumour. It is typically idiopathic and is likely autoimmune in origin. It can be secondary to drugs, inflammatory conditions, malignancy, haemorrhage, infection, radiation...[1, 2]
Although retroperitoneal fibrosis manifests as an isolated retroperitoneal disease, it can also be associated with other fibrosing conditions, such as sclerosing cholangitis, Riedel thyroiditis, fibrotic pseudotumour of the orbit, and autoimmune pancreatitis. [1, 2, 3]
Retroperitoneal fibrosis can be asymptomatic in the early stages, but pain, extremity swelling, decreased urinary output, and testicular swelling may be seen in the chronic stage. It is more common in men between 40 and 60 years of age.
It is seen most commonly surrounding the infrarenal abdominal aorta and proximal common iliac arteries.
CT shows an irregular plaque-like soft-tissue mass in the retroperitoneum, located around the aortic bifurcation and extending along the iliac arteries and involving the ureters, duodenum, pancreas, and spleen. Retroperitoneal fibrosis does not displace the aorta and IVC anteriorly, as lymphoma or metastatic nodes, but causes tethering of these structures to the underlying vertebrae. Avid enhancement is seen in the active stages of retroperitoneal fibrosis, with little or no enhancement in the chronic phase. MRI shows high signal intensity on T2-weighted images in the acute phase of the disease, with early contrast enhancement, and shows low signal intensity in the chronic fibrosing phase, with delayed enhancement. Gallium 67 examinations show high uptake in the active stages of the disease and little or no uptake in the chronic fibrotic stage. The FDG PET shows increased uptake of FDG and is useful for detecting metabolic activity and distant disease. [2, 3, 4 ]
Associated features that are suggestive of retroperitoneal fibrosis are abdominal aortic aneurysms, history of radiation exposure, and medial displacement of the ureters.
Malignant retroperitoneal fibrosis is produced when small retroperitoneal neoplastic foci elicit a desmoplastic response, and it may be difficult to distinguish from nonmalignant retroperitoneal fibrosis. Compared with nonmalignant retroperitoneal fibrosis, malignant retroperitoneal fibrosis is larger, with irregular lobular nodular margins, is located more cephalad, and shows mass effect, displacing the aorta and IVC anteriorly and the ureters laterally, with variable contrast enhancement.
In our case the diagnosis was confirmed by guided fine needle aspiration. Double J catheter was placed in each ureter to treat urinary tract obstruction and the mass was treated with corticosteroids.
Differential Diagnosis List
Renal insufficiency secondary to retroperitoneal fibrosis.
Retroperitoneal fibrosis
Lymphoproliferative syndrome
Solid retroperitoneal masses (neoplastic or nonneoplastic masses)
Cystic retroperitoneal masses (neoplastic or nonneoplastic masses)
Final Diagnosis
Renal insufficiency secondary to retroperitoneal fibrosis.
