Idiopathic retroperitoneal fibrosis: prospective evaluation of incidence and clinicoradiologic presentation.

Retroperitoneal fibrosis (RPF) is a rare disorder of unknown etiology. Its incidence is unknown, and the insidious and nonspecific nature of symptoms may contribute to considerable diagnostic delay. We conducted the current study to assess the incidence and clinicoradiologic characteristics of idiopathic RPF. For this, we evaluated prospectively 53 consecutive patients with a diagnosis of idiopathic RPF at our tertiary care referral center from April 1998 through January 2008.Calculated annual incidence of RPF was 1.3/100,000 inhabitants. Mean age was 64 +/- 11.1 (SD) yr; male-female ratio was 3.3:1.0. Median duration of symptoms was 6.0 mo (IQR 3.0-12.0). Abdominal, flank, and/or back pain and discomfort were the major symptoms, with visual analogue scale scores of 49 +/- 27.2 mm and 43 +/- 29.4 mm for pain and discomfort, respectively. Female patients had higher erythrocyte sedimentation rate (ESR), higher white blood cell count, and lower hemoglobin content than male patients at presentation. Computed tomography-documented maximal mass thickness amounted to 35 +/- 16.6 mm; craniocaudal length amounted to 137 +/- 48.8 mm. RPF mass extension up to or above the level of the renal vessels was noted in 3 patients (6%). Six patients (11%) presented with atypical RPF localization and/or bulky mass. Localized lymphadenopathy adjacent to the RPF mass was observed frequently (25%). Patients with hydronephrosis (56%) presented earlier than patients without hydronephrosis, with higher creatinine and greater mass thickness but similar pain severity. Patients were typically at high cardiovascular risk with increased-often aneurysmal-infrarenal aortic diameter (25.0 mm, IQR 22.0-30.0). RPF mass distribution was similar in patients with or without aneurysmal dilation. Occupational asbestos exposure (20%) and asbestos-related pleural changes (17%) were frequent among males. Previous or concurrent chronic inflammatory disease and/or autoimmune disease was noted in 8 patients (15%). Multivariate analysis revealed an independent association of ESR values with severity of pain and discomfort. Smoking was independently associated with infrarenal aortic diameter.In summary, annual RPF incidence is higher than previously assumed. Age at diagnosis and male-female ratio seem to have changed over time. RPF typically affects patients at high cardiovascular risk, including increased aortic diameter. Clinical presentation is influenced by sex, severity of inflammation and presence of hydronephrosis. Prolonged asbestos exposure and asbestos-related pleural changes were frequent among males. Localized lymphadenopathy adjacent to the RPF mass occurs frequently and should not confuse RPF diagnosis.