Context: Little is known about the natural history of sporadic angiomyolipomas; there is uncertainty regarding the indications of treatment and treatment options. Objective: To evaluate the indications, effectiveness, harms and follow-up of different management modalities for sporadic AML to provide guidance for clinical practice. Evidence acquisition: A systematic review of the literature was undertaken incorporating Medline, Embase and the Cochrane Library (from 1 st January 1990 to 30 th June 2017) in accordance with PRISMA guidelines. No restriction on study design was imposed. Patients with sporadic AML were included. The main interventions included active surveillance, surgery (nephron-sparing surgery and radical nephrectomy), selective arterial embolization, and percutaneous or laparoscopic thermal ablations (radiofrequency, microwaves or cryoablation). The outcomes included: indications for active treatment, AML growth rate, AML recurrence rate, risk of bleeding, post treatment renal function, adverse events of treatments and modalities of follow-up. Risk of bias assessment was performed using standard Cochrane methods. Evidence synthesis: Among 2704 articles identified, 43 studies were eligible for inclusion (0 RCT, 9 non-randomized comparative retrospective studies and 34 single arm case series). Most studies were retrospective and uncontrolled, and had a moderate to high risk of bias. Conclusions: In active surveillance series, the spontaneous bleeding was 2% and active treatment was undertaken in 5% of patients. Active surveillance is the most chosen option in 48% of the cases, followed by surgery in 31% and selective arterial embolization in 17% of the cases. Selective arterial embolization appeared to reduce AML volume but required secondary treatment in 30% of the cases. Surgery (particularly nephron sparing surgery) was the most effective treatment in terms of recurrence and need for secondary procedures. Thermal ablation was an infrequent option. The association between AML size and the risk of bleeding remained unclear; as such the traditional 4 cm cutoff should not per se trigger active treatment. In spite of the limitations and uncertainties relating to the evidence base, the findings may be used to guide and inform clinical practice, until more robust data emerge. Patient summary: Sporadic AML is a benign tumour of the kidney consisting of a mixture of blood vessels, fat and muscle. Large tumours may have a risk of spontaneous bleed. However, the size beyond which needs to be treated remains unclear. Most small AMLs can be monitored without any active treatment. For those who need treatment, options include surgical removal or stopping its blood supply (selective embolization). Surgery has a lower recurrence rate and lower need for a repeat surgical procedure.
