Clinical History
The patient, coming from the Urology unit, suffered from retroperitoneal fibrosis treated to ensure ureteric patency and to protect kidney function with ureteric double-J stents inserted bilaterally. At admission he showed pain and swelling in the scrotum which, on palpation, had a hard consistency.
Imaging Findings
MR imaging examination on 1.5 T system, coil dedicated, on the axial, coronal and sagittal plans, using FSE T1W, T2W and Fat Suppression (Fat Sat T2W and STIR) sequences, were performed.
Diffuse fibrotic plaques were displayed against the scrotum, particularly on the left. These plaques spread to the right along the inguinal canal. The same were shown hypointense on T1 weighted images and of variable intensity on T2 weighted images and on Fat Suppression sequences (partly low and partly hyperintense signal). The MRI also showed a small bilateral hydrocele.
Discussion
Retroperitoneal fibrosis (RPF) was first described in 1905 by the urologist Albaran, but it became fully recognised in 1948, with the publication by Ormond [1]. Although its true incidence is unknown, estimates range from one case per 200, 000 to 500, 000 individuals per year. It occurs predominantly in men in their fifth and sixth decades of life, with a 3:1 male/female ratio [2]. Retroperitoneal fibrosis is generally idiopathic, but can also be secondary to the use of certain drugs, infections and surgery. The idiopathic form of the disease accounts in more than two thirds of cases and it is characterised by a white, woody and fibrous plaque that covers the retroperitoneal structures, i.e. the great vessels, ureters. It is usually centralised at the level of the fourth and fifth lumbar vertebrae and spreads down to the pelvis; rarely, it extends into the scrotum or continues above the diaphragm as fibrous mediastinitis. The clinical presentation of RPF is usually insidious with vague constitutional symptoms and generally low back pain that may be severe and non–responsive to anti–inflammatory drugs. The pathogenesis is still poorly elucidated, but recent evidence supports the hypothesis that the disease may be the result of an inflammatory state triggered by autoimmune responses. The introduction of medical therapy, mainly based on corticosteroids, has greatly improved the patients' outcome, and the availability of imaging techniques, such as CT and MRI, has provided non–invasive methods of diagnosis and follow–up [2]. On unenhanced CT, RPF appears as a plaque, isodense with muscle. After the administration of intravenous contrast medium, the plaque shows variable enhancement depending on the stage of the fibrotic process. In the early stages, the plaque is more vascular and enhances to a greater degree. At later stage, the avascular plaque shows poor enhancement. The MRI presents a contrast resolution much higher than that of CT, allowing to avoid the administration of the contrast medium. Retroperitoneal fibrosis has signal characteristics similar to those of other fibrotic processes, with a tendency toward diffusely low signal intensity on T1-weighted imaging. The T2 signal of this tissue may vary considerably, however, which is a reflection of the degree of associated active inflammation. Chronic, inactive fibrosis will have little oedema and thus be visualised as having low signal on both T1- and T2-weighted imaging. This feature may prove valuable in assessing a patient’s response to treatment; decreasing oedema, and thus T2-signal, indicates a favourable therapeutic response [2, 3]. Both surgical and medical managements have been used.
Differential Diagnosis List
Involvement of the scrotum in a patient with idiopathic retroperitoneal fibrosis
Retroperitoneal metastases or lymphoma
Retroperitoneal haemorrage
Final Diagnosis
Involvement of the scrotum in a patient with idiopathic retroperitoneal fibrosis
