What is a renal angiomyolipoma?

What is a renal angiomyolipoma?

In this article, we will describe 10 facts about renal angiomyolipoma.

1. What is an angiomyolipoma (AML)?

AML is a type of benign kidney tumour composed of blood vessels, smooth muscle cells, and fat cells. It is not a cancer.

They are called angiomyolipoma as they consist of thick walled blood vessels (‘angio’), muscle tissue (‘myo’) and fatty tissue (‘lipo’).

Angiomyolipomas can develop in different places in the body, but they mainly occur in the kidneys.

2. How common is AML?

AML is rare (30 per 100,000 population). But it is the most common benign tumour of the kidney. It is more common in  women than men.

It can occur sporadically or in association with genetic conditions like tuberous sclerosis complex (TSC).

3. Size variation

AMLs can vary greatly in size, ranging from small lesions to large tumours that can potentially rupture and cause significant bleeding.

4. Symptoms

Small AMLs may be asymptomatic and discovered incidentally during imaging tests for unrelated conditions. However, larger AMLs can cause symptoms such as:

• Abdominal or flank pain
• Palpable mass (a mass that can be felt)
• Haematuria (bleeding in urine)
• Newly diagnosed high blood pressure
• Anaemia
• Urinary tract infection (UTI)
• Fever.

Note. Wunderlich Syndrome. A large angiomyolipoma (40 mm or larger) can cause spontaneous retroperitoneal hemorrhage (bleeding behind the abdominal cavity), known as Wunderlich syndrome. Although rare, this condition can be life-threatening.

5. Diagnosis of AML

Diagnosis involves imaging studies such as ultrasound, CT scan, or MRI. These tests help to visualise the tumour and assess its size and characteristics.

Angiomyolipomas shown in CT scan (both sides)

Biopsy of the abnormality may be necessary to confirm the diagnosis.

6. Risk of haemorrhage

One of the significant risks associated with AML is spontaneous haemorrhage (bleeding), particularly in larger tumours. This risk can necessitate surgical intervention to prevent potentially life-threatening bleeding.

7. Treatment of AML

Treatment depends on various factors including the size of the tumour, presence of symptoms, and patient preferences. Options may include surveillance, embolisation to block blood flow to the tumour, radiofrequency ablation (RFA) or surgical removal.

8. Association with Tuberous Sclerosis Complex (TSC)

A significant proportion of AML cases are associated with TSC, a genetic disorder characterised by the growth of numerous noncancerous tumors in various organs.

Tuberous sclerosis complex (TSC, also known as Bourneville-Pringle disease or tuberose sclerosis) is a rare hereditary condition. This causes abnormalities in the skin, brain, kidneys and other organs. In tuberous sclerosis complex, renal angiomyolipomas often grow in both kidneys.

Renal angiomyolipomas can also occur in people with the rare lung disease lymphangioleiomyomatosis (LAM).

9. Hormonal influence

AMLs are known to express oestrogen and progesterone receptors, suggesting a potential hormonal influence on their growth. This is particularly relevant in cases occurring in women, especially during pregnancy when hormonal changes may accelerate tumour growth.

10. Prognosis

In general, AMLs have a good prognosis, especially when small and asymptomatic. However, the risk of haemorrhage in larger tumours underscores the importance of monitoring and appropriate management strategies.

Summary

We have described what is a renal angiomyolipoma. We hope it has been helpful.

Other resource

Review article: Shamam, 2023

Last Reviewed on 7 May 2024