CASE 11092 Published on 30.08.2013

Unusual appearance of retroperitoneal fibrosis

Section

Uroradiology & genital male imaging

Case Type

Clinical Cases

Authors

Robinson JF, Nyhsen C

Sunderland Royal Hospital,
Kayll Road, Sunderland, SR4 7TP
Email:john.robinson@doctors.org.uk
Patient

63 years, male

Categories
Area of Interest Kidney, Urinary Tract / Bladder ; Imaging Technique Nuclear medicine conventional, CT, Ultrasound
Clinical History
63-year-old gentleman with a background of hypertension and diabetes presented with recurrent urinary tract infections. On questioning there had been a history of macroscopic haematuria but no other sinister features identified and he gave no history of prior malignancy.
Imaging Findings
Ultrasound was challenging due to body habitus but moderate right sided hydronephrosis (Fig 1) was noted.

Abdominopelvic CT showed a 65 x 55 x 65 mm well defined (slightly heterogeneous but solid) soft tissue mass immediately anterior to the right psoas muscle and common iliac vessels (Fig 2). This was involving the right ureter and causing hydronephrosis. The right kidney was atrophied with considerable cortical loss (Fig 3). There was relatively sparse vascular calcification with no aneurismal vessels seen.

Histology from CT guided core samples showed dense collagenous tissue which was relatively acellular in many areas but in others there were ill-defined bundles of slender fibroblasts and a light diffuse infiltrate of lymphocytes & plasma cells: Findings consistent with retroperitoneal fibrosis. No evidence of malignancy.

DMSA showed only faint uptake in the area of the right kidney (normal left kidney) with a relative uptake of 6% Vs 94% (Fig 4).
Discussion
Retroperitoneal fibrosis is a rare condition the cause of which is uncertain. Most cases are idiopathic but there is an association with certain medications, inflammatory conditions, aneurysms and malignancy. [1]

The workup for these patients involves;
- a search for potential precipitants
- supportive measures to preserve renal function
- more definitive treatment with immunosuppression and/or surgical options.

The condition is important because of its potential sequelae (namely obstructive uropathy) and because of its associations (most pertinently malignancy). The mean survival being only a few months if associated with a malignancy (compared to potentially normal life expectancy with idiopathic retroperitoneal fibrosis) [2, 3].

If a judicious search for a precipitant reveals nothing untoward and imaging/biopsy findings are typical then the diagnosis of idiopathic retroperitoneal fibrosis is relatively safe. However, if radiological findings are atypical then making the correct diagnosis is more difficult.

Radiologically the typical findings of idiopathic fibrosis are of plaque-like soft tissue with peripheral infiltration centred around the aortic bifurcation. The vessels are generally tethered posteriorly and the ureters displaced medially. [3]

Large bulky lesions which displace vessels anteriorly and have a lobulated or nodular contour are less typical and some authors have suggested that these are features more suspicious of malignancy. [4, 5]

Histological diagnosis is necessary when the diagnosis is unclear but unfortunately there are diagnostic pitfalls here also [4, 6] as metastatic cells are often diffusely dispersed within the fibrotic plaque so false negative biopsies are possible.

Differentiating between benign and malignant disease is clearly important but can be extremely challenging and this case highlights these difficulties.

The lesion is unusually heterogenous and mass-like and in malignant retroperitoneal fibrosis negative biopsy results can be misleading (particularly given the small volumes achieved through percutanous biopsy).

On the other hand the biopsy results were not overtly worrying. Investigations did not reveal evidence of an occult malignancy elsewhere, CT appearances remained static on follow-up examinations and the patient remained well. Also, the appearances of the right kidney and collecting system suggested slow disease progression.

He was referred to the regional centre where radiological examinations and histology were reviewed. The diagnosis was felt to be correct and the decision was made not to proceed with surgical excision, particularly given his co-morbidities.
Differential Diagnosis List
Idiopathic retroperitoneal fibrosis
Retroperitoneal metastasis
Lymphoma
Primary retroperitoneal sarcoma
Final Diagnosis
Idiopathic retroperitoneal fibrosis
Case information
URL: https://www.eurorad.org/case/11092
DOI: 10.1594/EURORAD/CASE.11092
ISSN: 1563-4086