What is a Renal Angiomyolipoma: Causes, Symptoms, Classification, Diagnosis, Treatment and Prevention


They are the most common benign tumors suffered by the kidney and are composed of blood vessels, smooth muscle cells and fat cells, are strongly associated with the genetic disease of tuberous sclerosis , in which most individuals may have several angiomyolipomas that affect to both kidneys.

This tumor can develop anywhere in the body, such as the pancreas or the adrenal glands, but is predominantly seen in the kidneys.

They are also commonly found in women who have lymphangioleiomyomatosis (a lung disease).

Angiomyolipomas are rarely found in the liver and rarely in other organs. Whether associated with these diseases or sporadic, angiomyolipomas are usually caused by mutations in the TSC1 or TSC2 genes that regulate cell growth and proliferation.

Although they are considered benign, they can grow in such a way that the renal function deteriorates or the blood vessels dilate and can burst causing a hemorrhage.

Renal angiomyolipoma is one of the most common kidney tumors, since at least 1 percent of all kidney tumors are composed of aniomyolipoma.

This tumor occurs mainly in middle-aged individuals with an approximation of 4 men by 11 women.

Most angiomyolipomas are of sporadic origin, but a small number of patients with angiomyolipoma of the kidney are associated with a rare genetic disease called tuberous sclerosis complex.

Usually, the tumor develops only in one kidney. The sign and the common symptom include blood in the urine, frequent kidney infection, pain in the abdomen.

If the tumor enlarges in size, it can burst and cause profuse bleeding that can be life-threatening.

The treatment of choice is the complete surgical removal of the mass that may require a partial nephrectomy or, sometimes, total extirpation of the kidney with the lesion.

Recently, certain medications are also tested as a conservative option. The prognosis of the condition is good after the treatment, since the growth is benign.


The exact cause of angiomyolipoma of the kidney is not known, but it is thought to develop as a hereditary trait or it may be a sporadic event.

It is a benign tumor that is made up of blood vessels, smooth muscles and fat cells. Most cases of angiomyolipoma of the kidney are of sporadic origin and the rest may be associated with the tuberous sclerosis complex, a genetic disorder with gene mutation that occurs in the TSC1 and TSC2 gene.

Benign growth is usually seen more in women than in men because their formation occurs more rapidly in the presence of female hormones such as estrogen and progesterone.

The average age of their development is between 35 and 50 years. In addition to its association with tuberous sclerosis, some angiomyolipomas of the kidney are also associated with other genetic syndromes such as von Hipple Lindua disease and Struge Weber syndrome.

Due to the hormonal influence, the tumor tends to increase in size during pregnancy.


  • Fever.
  • Abdominal discomfort (a palpable mass when touching the abdomen).
  • Blood when urinating (hematuria).
  • Hypertension .
  • Around 25% of cases are complicated by spontaneous rupture that produces a spontaneous retroperitoneal hemorrhage (Wünderlich’s syndrome).

The angiomyolipoma of the kidney may appear on the outside of the kidney or in the internal area and the signs and symptoms may vary depending on the size of the tumor.

Sometimes, the growth remains asymptomatic if the size is too small. However, a growing tumor produces a constellation of symptoms.

Usually, a tumor larger than 4 cm will begin to produce unwanted symptoms. In most cases, only one kidney is affected. However, if it is associated with tuberous sclerosis, both kidneys have multiple angiomyolipoma.

The most common symptoms include:

  • Constant pain in the flanks and abdomen. The pain can be dull or sharp.
  • A palpable swelling in the lumbar area of ​​the spine. This is due to the enlargement of the growing tumor.
  • Urine red or brown due to the passage of blood in the urine.
  • Frequent infection of the urinary tract.
  • Elevation of blood presure.
  • The tumor grows in size during pregnancy.

A large, growing tumor may burst at some point and cause heavy bleeding that can lead to life-threatening complications.

How do doctors diagnose angiomyolipoma?

The preliminary diagnosis of angiomyolipoma is usually performed incidentally while the patient undergoes imaging tests for other reasons or directly by ultrasound, computed tomography and / or MRI scan.

The urologist, the radiologist and the emergency doctor are usually the first to suspect and / or diagnose these tumors.

The angiomyolipoma of the kidney is often exceptionally small and is only diagnosed by radiological imaging techniques, such as a CT scan or an ultrasound performed for some other reason.

In addition, doctors can find such tumors while doing ultrasound studies on pregnant women. Bleeding problems due to angiomyolipoma are rare but possible in pregnancy.


Angiomyolipomas are members of the group of perivascular epithelioid cell tumors (NCEP) and are composed of variable amounts of three components; blood vessels (-angio), cells filled with spindle (myo) and adipose tissue (lipo). Almost all angiomyolipomas are benign, but they are at risk of rupture with bleeding, damage or secondary destruction of the surrounding structures as they grow.

They are typically found in the kidney, but they have also been commonly found in the liver and less commonly the ovary, fallopian tube, spermatic cord, palate and colon.


Treatment varies depending on the size of the tumor and whether it remains stable over time or continues to grow. In tumors larger than 4 cm in diameter or growing, it is recommended to surgically remove them by interventional radiology, since they evolve more frequently to the appearance of other symptoms or hemorrhages.

Isolated and asymptomatic lesions of up to 4 cm can be periodically checked with ultrasound every 6 months or a year. In the case of bilateral tumors or in single kidneys, it must first be considered that renal functional reserve exists before deciding to eliminate it, in order to avoid later problems of renal failure.

Such a small and asymptomatic angiomyolipoma may only need to wait and observe. The size of the tumor is monitored regularly by the doctor.

However, surgery is needed for a growing tumor, in which case, the tumor is completely removed.

During surgery, a part of the kidney may also have to be removed depending on the area of ​​the invaded kidney.

Another treatment is embolization (technique in which the blood vessels in an angiomyolipoma tumor are sealed); this technique can be preventive and its use is suggested in angiomyolipomas of 4 cm in diameter or more to reduce the risk of hemorrhage (rupture of the vessel).

Today there are newer medications available that can help treat the condition conservatively.

It can be treated with the drug everolimus (Afinitor) that works by blocking the rapamycin protein to affect many processes involved in cell growth.

The researchers suggest that even if it is asymptomatic, angiomyolipoma that grows to 3 cm or more in diameter should be treated.

Patients with renal angiomyolipoma tumors that are small and asymptomatic should be routinely seen with follow-up visits and measures of angiomyolipoma tumor size, since some can rapidly develop a growth rate of up to about 4 cm per year.

What is the prognosis of angiomyolipoma?

In general, the prognosis of renal angiomyolipoma is good as long as the tumors do not have dilated blood vessels or grow rapidly.

However, the prognosis decreases if the tumor enlarges or if it compromises kidney function, so it may be necessary to remove it or the patient needs dialysis.

In addition, if the patient develops a hemorrhage, the prognosis, if the patient is not diagnosed and treated quickly, is regular or deficient.

Is it possible to prevent angiomyolipoma?

Although it is not possible to prevent the development of angiomyolipomas, it is possible to reduce the possibility that they may cause serious problems.

For example, asymptomatic renal angiomyolipoma can be treated before it has the opportunity to present symptoms, thus avoiding the symptoms and signs of angiomyolipoma.