<h1>Definition of Angiomyolipoma of the Kidney</h1><p>Angiomyolipoma of the kidney is a rare benign <a href="http://www.urology-textbook.com/renal-tumor.html"><u><font color="#0066cc">renal tumor</font></u></a> with a high fat content. </p><h3>Epidemiology of Renal Angiomyolipoma</h3><h4>Preval‎ence:</h4><p>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. </p><h4>Tuberous sclerosis:</h4><p>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. </p><h2>Etiology and Pathology of Angiomyolipoma </h2><h3>Etiology:</h3><p>Angiomyolipomas derive from perivascular epithelioid cells and grow probably hormone-dependent.</p><h3>Gross Pathology of Angiomyolipoma:</h3><p>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. </p><h3>Histology of Angiomyolipoma:</h3><p>Mature fat cells, smooth muscle cells, (atypical) blood vessels, occasional mitoses. </p><h2>Signs and Symptoms of Angiomyolipoma of the Kidney </h2><ul title="symptoms of renal angiomyolipomas"><li><a href="http://www.urology-textbook.com/abdominal-pain.html"><u><font color="#0066cc">Flank pain</font></u></a></li><li>Potentially life-threatening hemorrhage due to spontaneous rupture into the retroperitoneum (Wunderlich's syndrome). Pregnancy increases the risk of rupture.</li></ul><h2>Diagnosis of Renal Angiomyolipoma </h2><h3>Sonography of the Kidney:</h3><p>Sonography of the kidneys shows an echogenic mass in the kidney, caused by the high fat content.</p><h3>CT-Abdomen:</h3><p>The fat content typically causes a hypodense mass in the kidney with -20 to -80 HU, this enables the differentiation to <a href="http://www.urology-textbook.com/renal-cell-carcinoma.html"><u><font color="#0066cc">renal cell carcinoma</font></u></a> [fig. <a href="http://www.urology-textbook.com/angiomyolipoma-kidney.html#Angiomyolipom_CT1"><u><font color="#0066cc">CT of angiomyolipoma</font></u></a>]. Calcifications are rare in renal angiomyolipoma. </p><p><br></p><div><a name="Angiomyolipom_CT1"></a> <table><tbody><tr><td width="50%"><img alt="fig. CT abdomen of renal angiomyolipoma" src="https://img1.daumcdn.net/relay/cafe/original/?fname=http%3A%2F%2Fwww.urology-textbook.com%2F01%2FAngiomyolipom_CT1.jpg"></td><td width="5%" style="width: 37px;"> </td><td width="45%" style="width: 315px; vertical-align: bottom;"><p><strong>Fig. CT abdomen of renal angiomyolipoma:</strong> visible are hypodense fatty portions of the kidney tumor. By courtesy, Dr. G. Antes, Kempten. </p></td></tr></tbody></table></div><p><br></p><h3>MRI Abdomen:</h3><p>MRI enables the reliable detection of fat, which is typical for angiomyolipoma, and allows the differentiation to a renal cell carcinoma. </p><h3>Angiography:</h3><p>Neovascularization, similar to renal cell carcinoma, are possible. Angiography has no role in the differential diagnosis of renal tumors. </p><h2>Treatment of Renal Angiomyolipomas</h2><h3>Conservative Treatment of Angiomyolipomas:</h3><p>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%.</p><h3>Partial Nephrectomy:</h3><p><a href="http://www.urology-textbook.com/open-partial-nephrectomy.html"><u><font color="#0066cc">Partial nephrectomy</font></u></a> is indicated in angiomyolipomas of >4 cm, severe symptoms or in tumors of uncertain diagnosis.</p><h3>Selective embolization:</h3><p>Selective embolization is a possible minimally invasive treatment option. Sometimes, a relapse is possible after embolization. Rarely, percutaneous drainage of necrosis is necessary. </p><h3>Emergency nephrectomy:</h3><p>Nephrectomy is necessary in rupture of angiomyolipoma with life-threatening bleeding. <br></p>
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