An Uroradiology case of Angiomyolipoma

Clinical History

A 41 year old woman was admitted to the emergency department with pain in the right iliac fossa.Transabdominal US was performed and found a large highly hyperechoic mass of the right kidney.

Imaging Findings

A 41 year old woman was admitted to the emergency department of our hospital because of acute pain in the right iliac fossa. Laboratory and culture tests were negative. A transabdominal US was performed at our department and was found a large, highly hyperechoic mass of the upper pole of the right kidney protruded 5x4cm, well demarcated(fig. 3,4,5). There was following abdominal CT GE Prospeed spiral 10/10mm sections and was confirmed a mass with mixed hyperdense and fatty tissue elements (fig. 1,2). There was both satisfactory renal secretion and filling of urinary bladder. There was not any evidence of lymph nodes enlargement or any other evidence of space occupying lesion in the whole abdomen. A follow up was recommended.

Discussion

Angiomyolipoma is a benign renal neoplasm composed of fat, vascular, and smooth muscle elements. It has an incidence of about 0.3-3%. Two types are described: isolated angiomyolipoma and angiomyolipoma that is associated with tuberous sclerosis. Isolated angiomyolipoma occurs sporadically. It is often solitary and accounts for 80% of the angiomyolipomas. The mean age at presentation of patients with isolated angiomyolipoma is 43 years; this neoplasm is about 4 times more common in women than in men. Interestingly, 80% of the cases involve the right kidney. Angiomyolipoma that is associated with tuberous sclerosis accounts for 20% of angiomyolipomas. The lesions are typically larger than isolated angiomyolipomas, and they are often bilateral and multiple. Angiomyolipomas occur in 80% of patients with tuberous sclerosis. The male-to-female distributions of angiomyolipoma in patients with tuberous sclerosis are nearly equal, but the prevalence is higher in women. Angiomyolipomas occur in young women with lymphangiomyomatosis without other stigmata of tuberous sclerosis. Although angiomyolipomas are considered benign, rare cases that are possibly related to multicentric disease have been reported regarding extension into the renal vein, the inferior vena cava (IVC), or both; deposits in the regional lymph nodes have also been reported. Angiomyolipomas are benign tumours; the majority are small and single, although they vary in size from a few millimetres to larger than 20cm. The blood vessels in angiomyolipomas frequently have an angiomatous. The blood vessels do not have elastic tissue, but they do have a disorganized adventitial cuff of smooth muscle. Angiomyolipomas do not have a capsule, but they often are well emarginated; the majority (88%) extend through the renal capsule into the perinephric space. In addition, angiomyolipomas are slow growing and are truly space occupying; angiomyolipomas displace the renal parenchyma and distort the collecting system, sometimes causing renal destruction. The characteristic absence of elastic tissue in the tumour vessels predisposes the patient to aneurysm formation and spontaneous haemorrhage. Although the natural history of renal cell carcinoma in tuberous sclerosis is not well known, the risk of metastases likely increases with the size of the tumour; the risk is probably very low in tumours that are <3 cm in diameter. Apart from this group with tuberous sclerosis, follow-up may be reasonably restricted to patients with sporadic tumours >4 cm in diameter, in whom the incidence of hemorrhagic complications is higher.

Differential Diagnosis List

Final Diagnosis

Renal Angiomyolipoma

URL:	https://www.eurorad.org/case/7514
DOI:	10.1594/EURORAD/CASE.7514
ISSN:	1563-4086