ArticlesAsbestos exposure as a risk factor for retroperitoneal fibrosis
Introduction
Idiopathic retroperitoneal fibrosis, Ormond's disease, is a rare condition that was first described by Albarran in 1905,1 with comprehensive characterisation by Ormond2 in 1948. The pathognomonic feature of retroperitoneal fibrosis (RPF) is a thick retroperitoneal fibrotic mass covering the abdominal aorta and compressing the ureters (figure). The process of fibrosis can result in obstruction of the ureters and renal failure. The main treatment options include surgical liberation of the ureters and systemic administration of corticosteroids. Investigators have reported remission rates exceeding 90%.3
Previous work on the cause of this disease have been mainly case reports and series, which indicate that RPF can be induced by different factors. About a third of cases develop as a result of malignant disease, radiation therapy, abdominal surgery, pancreatitis, haematomas, and infections.4, 5 RPF has also been associated with the use of several drugs, especially methysergide and other ergotamine derivates.6
Little is known about the role of occupational factors such as asbestos exposure in RPF. Asbestos fibres cause interstitial lung fibrosis (asbestosis), pleural fibrosis, pleural plaques, lung cancer, and pleural and peritoneal mesothelioma.7 Asbestos exposure has been proposed as a causal factor for pleural and retroperitoneal fibrosis in three previous case reports.8, 9, 10 RPF has been suggested as the most severe form of chronic periaortitis, caused by the autoimmune response to the components of atherosclerotic plaques.11 The histological appearances of RPF and atherosclerotic chronic periaortitis are often identical.12 An association between abdominal aortic aneurysms and RPF has also been shown.5
The inflammatory nature of idiopathic RPF is supported by an elevated erythrocyte sedimentation rate at presentation and positive antinuclear antibodies,13 good response to anti-inflammatory drugs, and an occasional association with different autoimmune diseases.14 However, in most cases, the causative factors remain elusive. Our aim was to assess the aetiological significance of occupational asbestos exposure in the development of RPF in a case-control study.
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Methods
Patients
We selected all adult patients alive with RPF diagnosed and treated in 12 secondary and tertiary hospitals within three university hospital districts in Finland in 1990–2001. The population of the catchment area was 3·62 million in 2001. Demographic data were obtained from Statistics Finland. The ethics committee of Tampere University Hospital approved the study plan.
Potential cases were retrieved from the hospital discharge data register. Case identification was based on diagnostic
Controls
For every case, five living controls matched for year of birth, sex, and central hospital district were randomly assigned from the Finnish population register centre. Matching for central hospital district was used to avoid bias from different industrial structures in the regions. At the time of enrolment, 1 597 483 people born in 1918–63 lived in the study area.
Data collection
A five-page questionnaire was sent to all patients and controls to obtain information about sociodemographic factors, smoking, and medical history (including chronic diseases, abdominal surgery, aortic aneurysm, migraine and migraine medication used, and other permanent medication and malignant diseases). A structured questionnaire with 21 questions compiled and validated by the Finnish Institute of Occupational Health15 was used for assessment of asbestos exposure.
Postal questionnaires are
Evaluation of asbestos exposure
Assessment of cumulative asbestos exposure was based on fibre-years as determined by an expert according to industrial hygiene knowledge of certain occupations. A fibre-year was defined as working in a full shift (40 hours per week) for 1 year at an average dust level of 1 fibre/mL of air. The cumulative dose of 10 fibre-years has been estimated to cause a 1% risk of developing clinically recognisable asbestosis.7 We defined three grades of cumulative exposure before obtaining data: 0=no
Analysis
We calculated age-standardised incidence using the European 5-year group standard population.17 Multivariate analysis was done with conditional logistic regression in STATA (version 7.0). The attributable fraction (proportion of cases caused by exposure) was calculated with the formula (OR-1)/OR and the population attributable fraction (PAF) was determined as q(OR-1)/OR, in which OR was the odds ratio and q was the proportion of cases exposed to the factor.18 In calculation of the CIs, q was
Role of the funding source
The funding sources of the study had no role in the study design, data collection, data analysis, data interpretation, or writing of the report.
Results
The age-standardised incidence of RPF was 0·10 (95% CI 0·07–0·14) per 100 000 person-years overall, 0·14 (0·08–0·21) for men and 0·07 (0·04–0·10) for women, in 1990–2001.
The prevalence of the disease was 1·38 per 100 000 inhabitants in the study area. 22 (51%) cases and 48 (27%) controls had a positive asbestos exposure history (table 2). Exposures exceeding 10 fibre-years were exclusively occupational (table 3). Asbestos exposure was strongly associated with RPF, with crude OR 4·2 (95% CI
Discussion
Occupational asbestos exposure seems to be an important risk factor for RPF. To our knowledge, in addition to our first report,8 only two case reports have been published that suggest asbestos exposure as a common cause for diffuse pleural thickening, pleural calcification, and RPF.9, 10
We recorded a nine-fold risk for RPF in association with ≥10 fibre-years of asbestos exposure. The fraction of exposed cases attributable to asbestos exposure was more than 80%. This fraction is equivalent to
References (29)
Bilateral uretral obstruction due to development and compression by an inflammatory retroperitoneal process
J Urol
(1948)- et al.
Asbestos and idiopathic retroperitoneal fibrosis
Lancet
(1995) - et al.
Evidence of autoimmunity in chronic periaortitis: a prospective study
Am J Med
(2003) - et al.
Asbestos in extrapulmonary sites: omentum and mesentery
Chest
(2000) - et al.
Continuing increase in mesothelioma mortality in Britain
Lancet
(1995) Rétention rénale par périurétérite; libération externe de l'urétere
Assoc Fr Urol
(1905)- et al.
Aetiopathogenesis and treatment of idiopathic retroperitoneal fibrosis
Ann Urol (Paris)
(1998) - et al.
The clinical significance of retroperitoneal fibrosis
Surgery
(1977) Retroperitoneale fibrosen: symptomatic, diagnostic, therapie, prognose
(1978)- et al.
Fibrotic disorders associated with methysergide therapy for headache
N Engl J Med
(1966)