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Findings in this case: Noncontrast CT scan of the abdomen. There is an inhomogeneous low density in the central portion of the RIGHT kidney with high density in the collecting system. Moderate RIGHT hydronephrosis. Angiomyolipoma in the upper pole of the LEFT kidney as well.
Diagnosis: Renal angiomyolipoma with hemorrhage.
File:5A
Organ system: 5.0 Genitourinary tract.
Organ: A. Kidney.
Information:
Etiology and incidence: 1) The most common benign renal neoplasm. 2) Angiomyolipomas of the kidney may occur with as an isolated process or associated with tuberous sclerosis. 3) Angiomyolipomas associated with tuberous sclerosis are usually bilateral and multifocal. Presentation is variable due to evaluations associated with the tuberous sclerosis process. 4) Greater than 90% of reported cases of angiomyolipoma are isolated. 80% of tuberous sclerosis patients will have angiomyolipomas. 5) Angiomyolipomas are seen more commonly in females than males if isolated and approximately equally if associated with tuberous sclerosis. Average age at diagnosis is middle-age to 70 years old for isolated cases.
Diagnosis: 1) Angiomyolipomas are typically asymptomatic. 2) Presenting symptoms when present include abdominal pain, flank pain, hematuria, hemorrhage and palpable mass. 3) Differential diagnosis: The presence of a large quantity of fat within a mass is diagnostic of an angiomyolipoma however retroperitoneal liposarcoma can appear to represent an exophytic angiomyolipoma. Renal carcinoma can contain fat. Additionally, though rarely, renal lipoma/liposarcoma, Wilms tumor, teratoma, oncocytoma and xanthogranulomatous pyelonephritis can contain moderate quantities of fat and present a difficult differential diagnosis. Some angiomyolipomas contain only small quantities of fat and differential diagnosis includes all of the above tumors. A differential point in favor of angiomyolipoma is a mass which does not contain any calcification, which is rare in angiomyolipomas. 4) CT: Predominantly fatty mass is the most typical appearance. Most commonly single. Most commonly less than 4 cm. The bilateral or multiple, suspect tuberous sclerosis; a) Less than 10% have very little fat; b) Calcification is rarely seen; c) The enhancement pattern can be variable. The higher the degree of soft tissue, the greater the enhancement. 4) Ultrasound: Parenchymal or exophytic echogenic mass with overall echogenicity similar to that of the renal hilum. Color Doppler can be used to evaluate for A/V fistula and/or aneurysm. 5) MRI: Heterogeneous mass secondary to a combination of fat and soft tissue. Vessels can demonstrate variable signal intensity secondary to flow rate. Enhancement rates and heights are similar to that for CT.
Prognosis/Clinical: 1) The most serious complication is hemorrhage. This is typically related to the size of the angiomyolipoma with masses greater than 4 cm being at higher risk for hemorrhage. Hemorrhage can be into the collecting system, external or both. 2) While considered benign, angiomyolipomas can grow over time and there can be invasion of the inferior vena cava and regional lymph nodes. There is no malignant potential if the angiomyolipoma occurs as an isolated process, however if associated with tuberous sclerosis, there is a small potential for malignant transformation and more strange and follow-up is necessary.
Treatment: Greater than 4 cm, or if there has been a bleeding or if the patient is having pain which is difficult to control clinically, embolization via interventional radiology can be performed. Preoperative embolization is also of help if surgery is contemplated.
References:
Renal angiomyolipoma with bleeding
M Muttarak MD, N Pattamapaspong MD, B Lojanapiwat MD, B Chaiwun MD
Received 15 December 2006; received in revised format 12 February 2007; accepted 23 February 2007
http://biij.org/2007/4/e8/e8.pdf
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