The Risks of Renal Angiomyolipoma: Reviewing the Evidence

Abstract

Renal angiomyolipoma (RAML), though a rare benign tumor, may impose a significant morbidity or even mortality due to its unique characteristics and the complications subsequent to its treatment. The classic tumor variant is composed of smooth muscular, vascular, and fatty components. The most straightforward diagnosis is when the fat component is abundant and gives a characteristic appearance on different imaging studies. In fat-poor lesions, however, the diagnosis is difficult and presumed a renal cell carcinoma. Yet, some variants of RAML, though rare, express an aggressive behavior leading to metastasis and mortality. The challenge lies in the early detection of benign variants and identifying aggressive lesions for proper management. Another challenge is when the vascular tissue component predominates and poses a risk of hemorrhage that may extend to the retroperitoneum in a massive life-threatening condition. The predicament here is to identify the characteristics of tumors at risk of bleeding and provide a prophylactic treatment. According to the clinical presentation, different treatment modalities, prophylactic or therapeutic, are available that span the spectrum of observation, embolization, or surgery. Renal impairment may result from extensive tumor burden or as a complication of the management itself. Improvement of diagnostic techniques, super-selective embolization, nephron-sparing surgery, and late treatment with the mammalian target of rapamycin inhibitors have provided more effective and safe management strategies. In this review, we examine the evidence pertaining to the risks imposed by RAML to the patients and identify merits and hazards associated with different treatment modalities.

Renal Angiomyolipoma: The Good, the Bad, and the Ugly

“…Many clinicians favour embolization and reserve surgery for patients with uncontrollable symptoms, vascular malformations, failure of embolization, and rare diagnostic uncertainty. When surgery needs to be performed, preoperative embolization of the lesion may be taken into consideration in reducing the difficulty and complications of tumourectomy or nephrectomy [11192732]. …”

“…Routine prophylaxis, including antipyretics, antiemetics and analgesia, may play a role in periprocedural management [227]. Other complications, including non-target embolization of normal parenchyma or renal infarction with abscess forming, are uncommon [111932]. In general though, arterial embolization is a well-tolerated procedure.…”

“…The effect of embolization may vary, because of the varying amounts of adipose, vascular, and smooth muscle tissue in the lesions. Different authors showed in their series a need for reembolization varying from 17% till 37% [323334]. …”

“…Nephrectomy is indicated only when a renal AML is very large, when suspicion of malignancy is high, and when other treatment options cannot be performed. However, in an emergency setting, a nephrectomy can be lifesaving [3132]. …”

Continuous Low-Dose Everolimus Shrinkage Tuberous Sclerosis Complex-Associated Renal Angiomyolipoma: A 48-Month Follow-up Study

“…The majority of the patients at risk face significant morbidities with increasing age 1. The vascular component of these neoplasms makes them susceptible to bleeding, and larger AML often develop aneurysms that may complicate renal vascular rupture 2. It may be more rational to use an mTOR inhibitor to minimize associated complications of AML 3.…”