Bilateral giant renal angiomyolipomas

Clinical History

A previously healthy 58 year old women presented with a one month history of hematuria and recurrent mild bilateral flank pain.

Imaging Findings

A previously healthy 58 year old women presented with a one month history of hematuria and recurrent mild bilateral flank pain. The patient was referred for an ultrasound of the abdomen which showed multiple ecogenic foci on the liver and heterogenous, predominantly echogenic masses in the locations of both kidneys. Color Doppler ultrasonography (GE loqic 500 Pro) performed using 3.5-5 multifrequency convex transducer revealed arterial flow on multiple sides of the tumors. CT demonstrated the presence of fat within the tumors and also the fat replacement of the parenchyma. MR showed bilateral huge renal masses predominantly of fat signal intensity on T1 and T2 weighted sequences.

Discussion

Angiomyolipomas are uncommon, benign tumors of the kidney composed of varying proportions of mature adipose tissue, smooth muscle cells, and blood. They are are usually found as solitary lesions in middle-aged woman and most often detected as incidental findings 0n US or CT examination for unrelated causes. Sporadic angiomyolipomas account for 80%-90% of the reported cases whereas the remaining cases of angiomyolipoma involve patients diagnosed for tuberous sclerosis, approximately 20%-50% of whom prove to have single, multiple, or bilateral angiomyolipomas of the kidneys. Such angiomyolipomas are generally different from isolated cases, because they tend to present at a younger age, have a higher incidence of bilateral renal involvement, are more symptomatic and they are larger tumors that are more likely to grow, and frequently require surgery. When symptoms do occur, the most common complaints include acute flank pain and hematuria related to spontaneous intratumoral or extrarenal hemorrhage. However our case was diagnosed in an older age, but in her history she had recurrent flank pain for many years, but she never had a radiologic investigation. The largest renal angiomyolipoma ever reported is by Katz, which was measuring 45X20X15 cm and weighing 3,500 g in a patient with tuberous sclerosis. Our case is not as big as this one, but we found quite large masses bilaterally, measuring 22X14X15 cm at left and 14X10X11 cm at right in a patient also with tuberous sclerosis. Angiomyolipomas, are well known to radiologists, despite being uncommon and of limited clinical importance, they represent one of the few lesions for which a spesific diagnosis can be achieved on the basis of radiologic findings specially with sectional imaging technics. There is a spectrum of sonographic findings in angiomyolipomas, based on fat content and the possible presence of hemorrhage. Tumors containing primarily fat are intensely echogenic, similar to renal sinus fat. Neoplasms with fat and hemorrhage reveal highly echogenic and echo-poor areas. A densely echogenic mass as detected on sonography is most likely an angiomyolipoma, but this finding is not pathognomonic because occasionally, a renal cell carcinoma can also be highly echogenic; hence CT is essential for positive identification of fat. CT documents distinctly negative attenuation values corresponding to the presence of fat within tumors. Detecting the existence of fat in a renal lesion will establish the diagnosis of angiomyolipoma and is the only radiologic finding that can differentiate it from renal cell carcinoma. In our case, tumors on both sides were homogeneously composed of fat, so we measured low Hounsfield numbers in every part of the tumors. A renal lipoma can mimic an angiomyolipoma on CT, despite its hypovascularity, but it is rare tumor, and its treatment would be similar to that of an angiomyolipoma. A well differentiated, low-grade liposarcoma can potentially resemble an angiomyolipoma on CT. However, the liposarcoma is a rare lesion, and it should be distinguishable from an angiomyolipoma on angiography, as typical angiomatous elements will be seen only in angiomyolipomas. An angiomyolipoma will also show as a defect in the renal parenchyma, indicating its renal origin, which a retroperitoneal liposarcoma cannot duplicate. MR imaging can diagnose angiomyolipoma if fat can be identified within the tumor. Because of its short T1 relaxation time, fat will demonstrate marked hyperintensity on T1-weighted images. There can be confusion between fat and hemorrhage, which may also demonstrate hyperintensity on T1-weighted images. However, fat and hemorrhage can usually be differentiated with heavily weighted T2 SE pulse sequences, the presence of a chemical shift artifact, or special imaging techniques such as proton spectroscopic imaging. We did not identify any focus of hemorrhage in any of the tumors on both sides. The benign nature of these tumors necessitates a conservative approach, and surgery is only necessary in large, symptomatic tumors. Angiography sometimes may be used as a part of treatment in selected cases. Our case was treated by left total nephrectomy andtumorectomy conserving as much renal tissue as possible.

Differential Diagnosis List

Final Diagnosis

Bilateral renal angiomyolipomas associated with tuberous sclerosis

URL:	https://www.eurorad.org/case/762
DOI:	10.1594/EURORAD/CASE.762
ISSN:	1563-4086