Surveillance imaging for sporadic renal angiomyolipoma less than 40 mm: lessons learnt and recommendations from the experience of a large district general hospital.

Introduction Sporadic renal angiomyolipomas, although benign in natural can cause life-threatening spontaneous haemorrhage. Surveillance of smaller lesions is recommended but there is no guidance on the surveillance interval or modality. Our aim was to study our sporadic angiomyolipoma population to determine the growth rate, factors that were associated with a higher growth rate and design a surveillance programme. Materials and methods All sporadic renal angiomyolipomas diagnosed between September 2009 and March 2015 were included. Patients with a diagnosis of tuberous sclerosis were excluded. Results A total of 217 sporadic renal angiomyolipomas were diagnosed. The median follow-up was 24 months (range 10-118 months). The median size at diagnosis was 9.00 mm with a mean growth rate of 0.13 mm/year (standard deviation 0.88). One hundred and fifty angiomyolipomas (69%) were shown to have negative or zero growth. In the remaining 67, 59 had a growth rate of less than 2.00 mm/year. Size of angiomyolipoma, tumour burden and age were not associated with a higher growth rate on multivariate analysis. Conclusion The majority of sporadic angiomyolipomas are small and do not grow. Our practice is to perform surveillance for those greater than 20 mm, with five-yearly ultrasound scans for 21-29 mm, and two-yearly surveillance for 30-39 mm tumours.