Angiomyolipoma of the Kidney

Review literature: (Oesterling et al, 1986).

Definition of Angiomyolipoma of the Kidney

Angiomyolipoma of the kidney is a rare benign renal tumor with a high fat content.

Epidemiology of Renal Angiomyolipoma

Prevalence:

The prevalence in autopsies is 0.3%, with ultrasound screening 0.1%. Women are much more frequently affected than men. Age peak 50–60 years.

Tuberous sclerosis:

45–80% of patients with tuberous sclerosis have (bilateral) asymptomatic angiomyolipomas. In tuberous sclerosis, there is an equal distribution between men and women, age peak 30 years.

Etiology and Pathology of Angiomyolipoma

Etiology:

Angiomyolipomas derive from perivascular epithelioid cells and grow probably hormone-dependent.

Gross Pathology of Angiomyolipoma:

Angiomyolipomas are grey-yellow lesions without a tumor capsule, round to oval. Sometimes, angiomyolipomas show multi-center growth with involvement of lymph nodes without metastatic potential.

Histology of Angiomyolipoma:

Mature fat cells, smooth muscle cells, (atypical) blood vessels, occasional mitoses.

Signs and Symptoms of Angiomyolipoma of the Kidney

Flank pain
Potentially life-threatening hemorrhage due to spontaneous rupture into the retroperitoneum (Wunderlich's syndrome). Pregnancy increases the risk of rupture.

Diagnosis of Renal Angiomyolipoma

Sonography of the Kidney:

Sonography of the kidneys shows an echogenic mass in the kidney, caused by the high fat content.

CT-Abdomen:

The fat content typically causes a hypodense mass in the kidney with -20 to -80 HU, this enables the differentiation to a renal cell carcinoma [fig. CT of angiomyolipoma]. Calcifications are rare in renal angiomyolipoma.

Fig. CT abdomen of renal angiomyolipoma: visible are hypodense fatty portions of the kidney tumor. By courtesy, Dr. G. Antes, Kempten.

MRI Abdomen:

MRI enables the reliable detection of fat, which is typical for angiomyolipoma, and allows the differentiation to a renal cell carcinoma.

Angiography:

Neovascularization, similar to renal cell carcinoma, are possible. Angiography has no role in the differential diagnosis of renal tumors.

Treatment of Renal Angiomyolipomas

Conservative Treatment of Angiomyolipomas:

Annual imaging controls are possible with angiomyolipomas less than 4 cm and mild symptoms. The annual growth rate is about 5%, in tuberous sclerosis up to 20%.

Partial Nephrectomy:

Partial nephrectomy is indicated in angiomyolipomas of >4 cm, severe symptoms or in tumors of uncertain diagnosis [see chapter partial nephrectomy].

Selective embolization:

Selective embolization is a possible minimally invasive treatment option. Sometimes, a relapse is possible after embolization. Rarely, percutaneous drainage of necrosis is necessary.

Emergency nephrectomy:

Nephrectomy is necessary in rupture of angiomyolipoma with life-threatening bleeding.

Renal oncocytoma

Index

Renal diseases

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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References

Oesterling u.a. 1986 OESTERLING, J. E. ; FISHMAN, E. K. ; GOLDMAN, S. M. ; MARSHALL, F. F.:: The management of renal angiomyolipoma.
In: J Urol
135 (1986), Nr. 6, S. 1121–4

Deutsche Version: Angiomyolipom der Nieren

Last update

Dr. med. Dirk Manski
man...@urologielehrbuch.de