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Angiomyolipoma: Changes in Kidney Structure Caused By It, Causes, Symptoms, Treatment

Angiomyolipoma is a most common kidney tumor often seen in female patients. The tumor contains muscle and fatty cells spread between adipose tissue and blood vessels. The angiomyolipoma of kidney is a benign and occasional bilateral tumor. The literature suggests tumor growth origin is mostly triggered by genetic abnormalities. We will discuss in this topic the cause, symptoms and treatment of angiomyolipoma and the changes in the kidney structure caused by Angiomyolipoma.


How Is Angiomyolipoma Defined?

Angiomyolipoma is a benign (slow growing) often-bilateral tumor of the kidney. Main components of the tumor are blood vessels, smooth muscle and fat cells. The scientific literature suggests Angiomyolipoma tumor is genetic disorder often spread into multiple organs. Angiomyolipoma is known as Tuberous Sclerosis when the tumor is simultaneously spread in brain and other organs. Though disease is more common in kidney and results in kidney malfunction.

Describe The Changes In Kidney Structure Caused By Angiomyolipoma?

  • The adipose (fat) and muscles cells multiply and grows between glomerulus and renal tubules.
  • Fat or adipose tissue and muscles encroach upon the glomerulus and renal tubules.
  • The spread of fat and blood vessels around glomerulus and renal tubule causes rupture of capillaries followed by hemorrhage.
  • The infiltration of fatty tissues and muscles cells also causes obstruction and compression of renal tubules.
  • Distal obstruction to flow of arterial blood results in blood vessel dilatation. Dilated blood vessels under higher pressure ruptures causing kidney hemorrhage.

What Causes Angiomyolipoma?

The cause of Angiomyolipoma is unknown though most of the literature suggests cause is genetic abnormalities triggering tumor growth. Majority of cases of Angiomyolipomas of around 85% are widespread and are identified in adults with an average age of 42 years, especially in females. Angiomyolipoma is also a multi-organ benign tumor spread in brain, kidney, lungs and liver.

What Are The Risk Factors for Angiomyolipoma?

The genetic abnormalities triggering growth of Angiomyolipoma is either inherited or follows viral infection. The risk factors are multiple as described below-

  • Gender- Most common in female
  • Age- Rare before puberty
  • Pregnancy- Dormant tumor becomes active during pregnancy.1
  • Spread- Angiomyolipoma may spread into surrounding tissue though it is a benign tumor.2

What Are The Symptoms of Angiomyolipoma?

Angiomyolipomas are usually identified when the kidneys are being checked for some other condition. The clinical presentation needing urgent investigation and treatment is spontaneous retroperitoneal hemorrhage. There are also instances of shock as a result of the hemorrhage of the vessels due to Angiomyolipoma. People may experience various other symptoms and signs like:

  • Palpable Mass- Asymptomatic tumor can grow into huge mass and may cause symptoms involving pressure on surrounding organ.3
  • Flank pain caused by pressure on surrounding nerve or expansion of kidney irritating nerves situated around kidney capsule.
  • Frequent urinary tract infections
  • Hematuria- Microscopic hematuria observed during early phase and frank hematuria is seen during late stage.
  • Renal Failure- Bilateral or huge tumor mass can cause renal failure.
  • Hypertension- Increased secretion of angiotensin hormone result in hypertension.
  • Anemia- Loss of blood in urine may result in anemia.

How is Angiomyolipoma Diagnosed?

Ultrasound Examinations for Angiomyolipoma

  • Ultrasound examination of kidney reveals increased size of kidney with tumor.
  • Ultrasound of brain, liver and other soft tissue are also performed to rule out tumor in other organs. Tuberous Sclerosis is often associated with Kidney Angiomyolipoma.

CT Scan for Angiomyolipoma

  • CT scan is done to examine the detailed structure of cortex and medulla of the kidney.
  • The maximum amounts of lesions are identified in the cortex.
  • Angiomyolipomas will appear as hyperechoic limited lesions, which will be located in the cortex.

MRI Scan for Angiomyolipoma

This study virtually confirms the presence of Angiomyolipoma.

  • Blood vessels are often defined better in MRI films.
  • Hemorrhage is also observed in MRI

Kidney Biopsy for Angiomyolipoma

  • Kidney biopsy is performed under the guidance of Ultrasound and CAT scan.
  • The microscopic study reveals tumor consisting of blood vessel fatty tissue and muscle fibers within kidney tissue thus the tumor is named Angio-Myo-Lipoma (Angio- blood vessels, Myo- muscles and Lipoma- fatty tumor).

How is Angiomyolipoma Treated?

Angiomyolipoma of large size is often diagnosed during routine annual visit. Treating physician mostly is unable to find small tumor during clinical examination. Small kidney tumor is often found during ultrasound or MRI examination when used to investigate other diseases. Following initial diagnosis periodic ultrasound and MRI examination are performed with frequency of every 6 to 12 months depending on rate of growth. If tumor growth is seems to be rapid or tumor is of significant size at the time of initial or follow up examination further treatment is advised.

Treatment of Large or Rapid Growing Tumor-

Embolization Procedure for Angiomyolipoma

  • Elective Embolization- Effective therapy to slow growth of the tumor mass.
  • Emergency Embolization- Profuse bleeding is treated by embolization. Procedure is useful to stop active bleeding resulting in emergency.

Surgical Treatment for Angiomyolipoma

  • Partial Nephrectomy- Large or bleeding tumor mass is removed.


1.Kidney angiomyolipoma in pregnancy.

Tupikowski K1, Biały A2, Dembowski J1, Złotkiewicz M2, Guziński M3, Kołodziej AK1, Zdrojowy R1.

Cent European J Urol. 2014;66(4):434-6.

2. Angiomyolipoma of kidney.

Eble JN.

Semin Diagn Pathol. 1998 Feb;15(1):21-40.

Jan 27.

3. Giant renal angiomyolipoma: unusual cause of huge abdominal mass.

Taneja R1, Singh DV2.

J Clin Imaging Sci. 2013 Nov 28;3:56.

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:January 23, 2019

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