Angiomyolipoma of the kidney: A common benign renal tumor

Last updated: March 6, 2024

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An incidentally finding kidney tumor which is very common at my urology office, that so-called Angiomyolipoma (AMLs) in medical term. This tumor mostly detected at health promotion clinic which is made the patients really concerned when their first met with me. And that is the reason that we are going to discuss today.

First of all, I need to confirm that Angiomyolipoma is a benign renal tumor. There were reports on 0.2% – 0.6% among general populations and most commonly found in middle-aged of female. Their etiologies divide into 2 categorizes

1. Sporadic or happens by itself without any causes – 80% of cases.
2. Generic-related diseases, tuberosclerosis (TSC) or pulmonary lymphangioleiomyomatosis (LAM) – 20% of cases.

Since the most of Angiomyolipoma is asymptomatic, around 85% of cases are always incidentally finding from medical check up imaging. On the other hand, 15% of cases will symptomatically present for example.

Symptoms of symptomatic Angiomyolipoma

• Spontaneous tumor hemorrhage
• Palpable flank mass
• Flank pain
• Bloody urination
• Urinary tract infection

Diagnosis – I can say that Angiomyolipoma can be diagnosed by pure imaging modality since they have a unique composition which is “Fat” so once the imaging can detect renal tumor with fat component, AMLs will be a diagnosis.

Investigation options – there’s a numbers of imaging modalities in current Angiomyolipoma practice and definitely they are all have pros and cons.

1. Ultrasound – The most common used modality at health promotion clinic.
   • Pros – Cheap, no radiation exposure, widely accessibility
   • Cons – Operator dependent procedure, less accuracy in small AMLs
2. Non-contrasted CT scan – Gold standard in AMLs diagnosis.
   • Pros – Definite investigation in AMLs, accurately diagnose AMLs
   • Cons – Radiation exposure, expensive
3. MRI – Alternative modality with comparatively accurate with CT scan.
   • Pros – Accurately diagnose AMLs
   • Cons – taking long investigation time, expensive, contraindicated in metallic implanted patients
4. Percutaneous biopsy – a rarely procedure in much selected case.
   • Pros – Tissue diagnosis
   • Cons – Risk of AMLs hemorrhage

Management options – There were a confirmed literatures stating that less than 4 cm of AMLs can be reassured with no needing to do interventions. In contrast, if more than 4 cm AMLs have been reported, the possibility rupture event will be. Here are all the treatment choices.

1. Active surveillance – Regularly monitoring the progression of an existing tumors and developments of the new one.
2. Embolization – Minimally invasive intervention is considered as first line treatment in AMLs which more than 4 cm. By the way, there is 42.8% chance of post procedure complication called “post embolization syndrome” – a self-limited condition, which is characterized by fever, flank pain, nausea and vomiting during the first 3 days after the procedure.
3. Surgery – Can be considered if malignancy more likely to be.
4. Thermal ablation – Promising intervention which use the effect of frost bite (Cryotherapy) or thermal burn (Radiofrequency ablation) are still little in clinical evidence.

The key message that urologist must let patients aware is that AMLs is a benign tumor which mostly need only an active surveillance program. Intervention is required in a rare case. See you in next topic!

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