Patterns of renal angiomyolipoma regression post embolisation on medium- to long-term follow-up

Abstract

Objective: To assess the patterns of regression of renal angiomyolipoma (AML) post embolisation and report the outcomes related to the use of different embolic materials.

Methods: A retrospective review of all patients who underwent embolisation for renal AML at our institution between January 2004 and April 2012.

Results: 13 patients underwent 16 episodes of embolisation. Coils were used as the primary embolisation material in 10 episodes and microspheres in 6 episodes. The size reduction rate highly correlated on CT follow-up between the two groups, with 25.6% vs 22.7% reduction at 12 months, 27.5% vs 25.1% at 24 months, 35.0% vs 33.0% at 36 months and 35.0% vs 36.8% at 48 months. During follow-up, all tumours reduced in size with one patient requiring subsequent embolisation whose tumour reduced by only 6.5% after 1 year and subsequently exhibited regrowth after 4 years. Two patients presented with rebleeding and underwent repeat embolisation. Our overall retreatment rate (23%) is well within the literature range (up to 37%). None of the patients underwent surgery.

Conclusion: The majority of AML shrinkage occurs within the first year following embolisation and appears to plateau after 3 years, which could have an impact on follow-up strategy. The percentage reduction at 1 year may reflect the long-term effect of embolisation with tumours demonstrating minor size reduction more likely to relapse at long-term follow-up. Embolisation of renal AML produces durable long-term results regardless of the choice of embolic agent.

Advances in knowledge: These findings provide information to guide CT follow-up of renal AML post embolisation.

Figure 1.

Digital subtraction angiogram prior to embolisation (a and b) shows hypervascular tumour with a single feeder vessel at the upper pole of the right kidney. (c, d) Marked reduction in vascularity post-selective embolisation with embosphere particles and microcoils.

Figure 2.

Pattern of percentage reduction (y-axis) in the size of renal angiomyolipomas on CT follow-up post embolisation (x-axis) demonstrates high correlation between the two groups (coils were used as the primary embolic agent in Group 1 and embosphere particles in Group 2).

Figure 3.

Suggested algorithm for follow-up post embolisation.

Figure 4.

Contrast-enhanced axial CT shows predominantly fatty angiomyolipoma before embolisation (a), which exhibited modest reduction in size 1 year post embolisation (b).

Figure 5.

Contrast-enhanced axial CT shows angiomyolipoma with a significant angiomyogenic component (a), which exhibited a marked reduction in size 2 years post embolisation with residual tumour mainly composed of fat (b).