British Journal of Radiology (2003) 76, 570-573
© 2003 British Institute of Radiology
doi: 10.1259/bjr/61286585
Idiopathic presacral retroperitoneal fibrosis: report of two cases
B K Park, MD,
S H Kim, MD and
M H Moon, MD
The Department of Radiology, Seoul National University College of Medicine, Institute of Radiation Medicine, SNUMRC, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
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Abstract
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Retroperitoneal fibrosis is characteristic plaques of dense fibrous tissue, typically extending from the level of the kidney down to the sacral promontory. Involvement of the presacral space is extremely rare in retroperitoneal fibrosis. We report two cases of idiopathic retroperitoneal fibrosis manifested by a presacral mass.
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Introduction
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Retroperitoneal fibrosis (RPF) is usually centred over the anterior surfaces of the fourth and fifth lumbar vertebra surrounding the great vessels and ureters [1]. RPF localized to the presacral region is rare. We report the imaging findings of two cases of RPF localized to the presacral region.
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Case reports
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Case 1
A 38-year-old man was admitted to hospital with lower abdominal pain and weight loss over a 3 week period. There was tenderness in the lower pelvis just above the symphysis pubis. Laboratory findings were normal.
Transrectal ultrasound showed a thick, homogeneous, hypoechoic mass with irregular infiltration in the space between the rectum and sacrum (Figure 1a
). The mass did not reveal blood flow signal on the colour Doppler ultrasound. Contrast-enhanced CT scan demonstrated the presacral soft tissue mass without evidence of bony destruction (Figure 1b).
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Figure 1. A 38-year-old male with presacral retroperitoneal fibrosis (case 1). (a) Transrectal colour Doppler ultrasound in transverse plane shows a homogeneous, hypoechoic mass with irregular infiltration in the space between the rectum and sacrum (arrowheads). The mass does not reveal flow signal. (b) Contrast-enhanced CT in the level of sacrum shows a presacral soft tissue mass infiltrating into the perirectal space (arrowheads). The bladder wall is thickened posteriorly (black arrowheads). (c) Photomicrograph ( x 200: haematoxylin–eosin stain) shows proliferative fibroblasts with inflammatory infiltrate of lymphocytes, plasma cells and eosinophils.
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On sigmoidoscopy, the rectum was normal except for indentation on the posterior wall, suggesting extrinsic compression. Needle biopsy was done under transrectal ultrasound guidance. Pathological examination revealed infiltration by chronic inflammatory cells with fibrosis, consistent with idiopathic RPF (Figure 1c
). The patient was treated with steroid therapy with symptomatic improvement. Unfortunately he was lost to clinical follow-up.
Case 2
A 55-year-old female presented with right flank pain. She had been taking anticonvulsive medication for temporal lobe epilepsy for 15 years. Physical examination showed oedematous lower legs. Cardiac and renal function was normal laboratory findings were normal.
Intravenous urography and retrograde pyelography revealed a right hydronephrosis and hydroureter with distal ureteric obstruction (Figure 2a). A contrast-enhanced CT scan demonstrated a thick, homogeneous, soft tissue mass covering the anterior surface of the sacrum (Figure 2b). MRI showed a crescent-shaped, flat mass along the anterior surface of sacrum. The signal intensity of the mass was low to intermediate on T1 weighted and T2 weighted images (Figure 2c, d). Contrast-enhanced T1 weighted MRI showed strong enhancement of the mass.
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Figure 2. A 55-year-old female with presacral retroperitoneal fibrosis (case 2). (a) Retrograde pyelogram shows obstruction of right pelvic ureter with smooth tapering margin (arrows). (b) Contrast-enhanced CT shows a thick, irregular-margined, soft tissue mass (arrowheads) anterior to the sacrum without bony destruction. Left ureter is well opacified (arrow) but the right ureter is not demonstrable. (c) T2 weighted and (d) contrast-enhanced T1 weighted sagittal MR images show a crescent-shaped soft tissue plaque (arrowheads) along the anterior surface of the sacrum. The lesion shows intermediate signal intensity on T2 weighted image and homogeneous enhancement on contrast-enhanced T1 weighted image. Note a signal-void structure (arrow) within the lesion that probably represent an encased vessel.
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The patient underwent adhesiolysis on the right distal ureter with multiple biopsies of the sacral mass, which was confirmed to be idiopathic RPF. The patient was treated with steroid medication and the presacral mass significantly reduced in size.
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Discussion
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The dense, greyish-white, fibrous plaque of RPF usually arises at or just below the level of the aortic bifurcation, near the sacral promontory or the lower lumbar vertebra. As the disease progresses, the plaque encases major vessels and ureters, extending adjacent to the aorta and its bifurcation. RPF may involve atypical sites including, small bowel mesentery, duodenum, colon, bladder and rarely the epidural space [2–4]. RPF confined to the presacral region without involvement of the usual site of origin is rare. To the best of our knowledge, the imaging findings of RPF confined to this unusual site have not been previously reported. In the present two cases, the lesions appeared as flat soft tissue masses composed of fibrotic tissue in the pelvic cavity covering the anterior surface of the sacrum.
Approximately two thirds of all cases RPF are considered idiopathic, the remaining third have causes including, a desmoplastic response to various malignancies and other inciting factors such as drugs or conditions such as infection, haemorrhage, or aneurysms [5–7].
RPF is relatively uncommon, with a prevalence of about one per 200 000 population [8]. Clinical signs and symptoms of RPF may be related to the entrapment and compression of the ureters, inferior vena cava, aorta and its branches, or gonadal vessels. However, clinical features are so non-specific that the diagnosis of RPF is usually suggested on the basis of radiographic findings [9].
Ultrasound can demonstrate smooth-bordered, hypoechoic mass with associated complications, such as hydronephrosis [10]. CT and MRI are regarded as the most useful imaging studies for diagnosing and determining the extent of RPF. The appearance on CT or MRI is that of a soft tissue mass enveloping the aorta and inferior vena cava and entrapping the ureters with consequent hydronephrosis [11, 12]. The attenuation of fibrous plaque on contrast-enhanced CT and the signal intensity on MRI (enhanced T1, T2 weighted images) are variable depending on the stage of the inflammatory process. Case 1 shows minimal enhancement of the presacral RPF on contrast-enhanced CT imaging, suggestive of a middle to late inflammatory stage of the disease. However, we were not able to correlate the degree of CT enhancement with histological features due to the limited biopsy specimens. Unlike Case 1, Case 2 shows an intermediate signal intensity of presacral RPF on T2 weighted MR images and strong enhancement on contrast-enhanced MR images, suggestive of an active inflammatory process. The histological features of the surgical biopsy showed good correlation with the signal intensity seen on MR.
Steroids and other immunosuppressive drugs have been used to treat idiopathic RPF. Intractable non-steroid responsive ureteral obstruction may require ureteric stenting or surgical freeing of the ureters from the plaque and transplanting them intraperitoneally to prevent recurrent involvement.
In conclusion, RPF confined to the presacral region is uncommon but should be considered in the differential diagnosis of a presacral mass if the lesion appears flat and extends over the anterior surface of the sacrum.
Received for publication July 2, 2002.
Accepted for publication November 27, 2002.
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References
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Abstract
Introduction
