Purpose Angiomyolipomas are rare benign renal tumors. To date only few studies have been published regarding the prevalence of sporadic angiomyolipomas that are not associated with genetic diseases such as tuberous sclerosis. The aims of our study were to calculate the prevalence and analyze the natural history of sporadic angiomyolipoma in a large patient population. Materials and Methods Abdominal ultrasound data of 61,389 patients (49.7 % women, 50.3 % men), consecutively collected from a

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... based, standardized documentation system (GE Healthcare Technologies, ViewPoint Bildverarbeitung GmbH, Weßling, Germany) from September 1, 1999 to December 31, 2012, were retrospectively analyzed. Results In the studied population, 270 cases of sporadic angiomyolipoma were identified representing a prevalence of 0.44 %, including 184 females and 86 males showing a prevalence of 0.60 % in the female and 0.28% in the male subpopulations. The mean tumor size of sporadic angiomyolipomas in our study was 10.8 mm ± 5.8 mm. The angiomyolipomas were located in 57.0 % of the cases in the right kidney, and 43.0 % in the left kidney. Only 14 (5.2 ) out of the 270 cases of AMLs occurred multiple and out of these 4 (1.5 %) were bilateral. in In 61 cases multiple examinations took place over a mean period of 25 months (ranging from 1 to 105 months). During the entire period no significant increase in tumor size has been documented (p=0.5263). Conclusion To our knowledge this is the largest prevalence analysis of sporadic angiomyolipoma to date. Our calculated prevalence is higher than previously reported prevalences on the basis of smaller studies. It is noticeable that females show a significantly higher prevalence than males. As reported in previous studies AMLs reveal no preference towards the left or right kidney, bilateral angiomyolipomas are rare and tumor growth in the long term is marginal.