British Journal of Radiology (2006) 79, e137-e139
© 2006 British Institute of Radiology
doi: 10.1259/bjr/31481042
Unusual appearance of retroperitoneal fibrosis simulating a tumour
C J Das, MD, DNB
1
R Sharma, MD
1
T P Jain, MD
1
V Rai, MS
2
S Chumber, MS
2 and
A K Das, MD
3
Departments of 1 Radiology, 2Surgery and 3Pathology, All India Institute of Medical Sciences, New Delhi, India
Correspondence: Dr Raju Sharma, Department of Radiology, All India Institute of Medical Sciences, New Delhi, India. E-mail: raju152{at}yahoo.com.
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Abstract
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Retroperitoneal fibrosis (RPF) is an uncommon entity that usually presents as a fibrous plaque-like lesion that encases the aorta and inferior vena cava below the level of the renal arteries. We present an unusual mass-like appearance of this disease simulating a tumour, with foci of calcification, seen in a young girl.
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Introduction
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Retroperitoneal fibrosis (RPF) is an uncommon disorder characterized pathologically by progressive connective tissue proliferation along the posterior aspect of the retroperitoneal cavity, but this rarely results in the formation of a mass. It is very difficult to distinguish RPF forming a mass from primary retroperitoneal tumour. Here we present the unusual appearance of RPF simulating a retroperitoneal tumour.
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Case report
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An 18-year-old female presented with history of intermittent right-sided lower abdominal pain for 3 months. There were no bowel or urinary complaints. Physical examination revealed a hard, fixed lump present in right lumbar region extending into right iliac fossa.
Plain radiograph of the abdomen was normal. Ultrasound of the abdomen with convex 3.5 MHz and linear 7 MHz transducers revealed a retroperitoneal hypoechoic mass lesion. Non-contrast CT of the abdomen showed a well-defined hypodense mass in the retroperitoneum caudal to the lower pole of right kidney encasing the ureter. Few areas of calcification were also seen within the mass (Figure 1
). Moderate enhancement of the mass was seen after intravenous contrast. MRI revealed well-defined low signal intensity mass compared with renal parenchyma on T1 weighted image (Figure 2a). The mass also appears as hypointense on T2 weighted image with few areas of hyperintensity seen peripherally (Figure 2b,c). Gradual enhancement was seen after intravenous gadolinium injection (Figure 2d). The proximal ureter and adjoining segment of inferior vena cava (IVC) were completely encased by the mass, causing hydronephrosis of the kidney. Based on imaging appearance, a provisional diagnosis of retroperitoneal fibrosis was suggested. The possibility of retroperitoneal fibromatosis and desmoid tumour was also kept in the differential diagnosis because of the T2 hypointensity of the lesion. The patient was subjected to a core biopsy (18G, BIRD) under ultrasound guidance. Histopathological examination showed features consistent with RPF. No evidence of malignancy was noted. At surgery, a hard, whitish, gritty tumour was found extending from below the right kidney up to the level of iliac crest. The tumour was encasing the right ureter and IVC. Right kidney was hydronephrotic. Most of the tumour could be excised except the part encasing the ureter and IVC. Radical resection was avoided as there was no histological evidence of malignancy. Percutaneous nephrostomy was performed to drain the hydronephrotic kidney. Her post-operative period was uneventful. Follow up CT done at 3 months interval did not show any significant change in size of the mass. The patient is doing well at 18 months clinical follow up and repeat imaging did not show any interval change in the size of the residual mass.
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Figure 1. Non-contrast CT of the abdomen shows a well-defined hypodense retroperitoneal mass (M) with foci of calcification (arrow), located anterior to the right psoas muscle.
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Figure 2. (a) Gradient echo (GRE) T1 weighted axial image shows a hypointense mass (M) in the right paracaval location. (b) GRE fat saturated T2 weighted axial image shows that the mass (M) is predominantly hypointense with few hyperintense foci in the periphery. (c) Tru-FISP coronal T2 weighted scan shows that the mass (M) is intimately related to right kidney (K) and is encasing the right ureter and compressing the inferior vena cava (IVC). (d) GRE post-contrast T1 weighted coronal scan shows an enhancing mass (M) abutting the right kidney (K) causing upstream hydronephrosis.
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Discussion
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RPF, also known as "Ormond's syndrome", is a rare disease with an estimated incidence of 1/200 000 population. Albarran reported the first documented case in 1905, and Ormond established the disease entity in 1948 [1]. Approximately two thirds of cases are considered idiopathic (primary RPF or Ormond's disease). The remaining one third of cases result from the use of illicit drugs (amphetamines, lysergic acid diethylamide), haemorrhage, surgery, infection, abdominal aortic aneurysm and desmoplastic reaction caused by malignant infiltration of the retroperitoneum from primary tumours of the breast, stomach, colon, lung and lymphoma [2]. Systemic fibrosing diseases associated with RPF are fibrous pseudotumour of the orbit, Riedel's thyroiditis, sclerosing cholangitis and mediastinal fibrosis [3].
RPF usually manifests as a fibrous plaque over the anterior surface of the lower lumbar vertebrae, below the renal arteries. This plaque may encase and compress the ureters, IVC and aorta, and characteristically causes medial deviation of the middle third of the ureter. Mass forming RPF is rare. Only 14 cases of localized mass forming RPF have previously been reported in literature [1, 4]. All of these patients, except one, underwent surgery or open biopsy due to a differential diagnosis of malignancy [1].
RPF is unusual before the age of 20 years or over the age of 70 years. The most common symptom is a dull, non-colicky and poorly localized back or flank pain. Other common symptoms include weight loss, anorexia, nausea or vomiting and malaise. The late complications of RPF result from the encasement of ureters, IVC, aorta and renal arteries, and rarely duodenum, biliary tract and pancreas [3].
The classic triad of urographic findings in RPF includes: delayed excretion of contrast material with unilateral (20%) or bilateral hydronephrosis, medial deviation of the middle one third of the ureter and tapered narrowing of the ureters at L4/5 level [3]. On retrograde pyelography, a 5 or 6 French catheter can be passed easily through the strictured segment [5]. Ultrasound shows fibrous plaque as a smooth bordered, relatively echo-poor mass anterior to the lower lumbar spine or sacral promontory in both benign and malignant RPF [5].
On non-contrast CT scans, RPF presents as a periaortic, plaque-like, soft tissue lesion of variable thickness that envelops the aorta and IVC between the renal hila and sacral promontory, and extends laterally to entrap the ureters, resulting in variable degrees of hydronephrosis. The mass tends not to displace the aorta anteriorly. It has the attenuation of muscle on unenhanced images. Calcification is rare in RPF; only a single case of RPF has yet been reported showing a small area of rim calcification in a retrocrural mass [4]. The early, active vascular stage shows significant enhancement, whereas the avascular later stage enhances very little. Malignant causes of RF cannot be differentiated from non-malignant causes based on CT findings [7].
On MRI, RPF is generally of low signal intensity on T1 weighted imaging. On T2 weighted imaging in the early active phase of RPF there is high signal intensity due to high cellularity and fluid content, while in late fibrous phase, signal intensity is low owing to increased deposition of fibrous tissue [3]. High signal intensity on T2 weighted imaging and inhomogeneity of plaque may indicate malignant RPF [6]. Except when the disease has reached a quiescent stage, both benign and malignant RPF usually enhance after intravenous gadolinium administration [6]. MRI has the added advantage of soft tissue contrast and it allows performing MR urography in the same setting. Moreover, it alleviates the need for administering iodinated contrast media to patients with potentially impaired renal function [4]. In our case, MRI accurately displayed the retroperitoneal mass of low signal intensity on T1 weighted image and predominantly low signal intensity on T2 weighted image with few areas of hyperintensity peripherally suggesting quiescent stage of RPF with few areas of ongoing activity peripherally. This MR picture was corroborated on histopathological findings. The imaging appearances of RPF can be mimicked by other conditions such as malignant lymphadenopathy, haemorrhage, infection and amyloidosis [4]. Typical RPF occupies the lower part of the abdominal aorta. However, mass forming RPF is usually located in the pelvic cavity or around the kidneys, as was seen in our case [8]. Fine needle aspiration cytology and biopsy, done under ultrasound or CT guidance, may be a useful diagnostic technique [1].
The unusual features of our case include the early age of presentation, unilateral asymmetric right sided location with a mass like presentation and presence of calcification. Buyl et al reported a case of unilateral periureteral RPF. The unilateral nature and periureteral location of their report is similar to our findings, but in their patient the lesion was less mass-like and did not contain any calcification [9].
Steroid therapy is effective for treating early stage RPF, as are other drugs like cyclosporine, cytotoxic agents and tamoxifen. Ureterolysis is performed for ureteral obstruction. If the pre-operative tests strongly suggest RF, a trial of steroid therapy may be worthwhile before surgery is carried out [1].
In conclusion, although RPF rarely forms a well-circumscribed localized mass in the retroperitoneum, it should be kept in the differential diagnosis of a retroperitoneal mass for proper evaluation and management.
Received for publication April 27, 2005.
Revision received June 30, 2005.
Accepted for publication December 9, 2005.
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References
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Abstract
Introduction
