Frequency of Angiomyolipomas Among Echogenic Nonshadowing Renal Masses (> 4 mm) Found at Ultrasound and the Utility of MRI for Diagnosis

The purpose of this study is to evaluate what percentage of echogenic nonshadowing renal lesions larger than 4 mm found at ultrasound are angiomyolipomas (AMLs) and to review how to diagnose AMLs, with particular emphasis on the increasing role played by MRI.

The study data were obtained at a single institution over a period of 45 months. Although some patients were being reviewed for specific symptoms, such as hematuria, pain, or recurrent urinary tract infections, most of the findings were incidental. Follow-up data on 158 lesions in 132 patients were available. Confirmation of diagnosis was made with follow-up imaging or with histopathologic examination.

Ninety-eight (62.0%) of the lesions were AMLs, eight (5.1%) were renal cell carcinomas, three (1.9%) were oncocytomas, 17 (10.8%) were artifacts, seven (4.4%) were fat, five (3.2%) were calculi, another eight (5.1%) were scars, and 12 (7.6%) were complicated cysts. The mean age of patients with AML was significantly lower than that of patients without AML (61.71 [SD, 13.25] years vs 68.80 [SD, 17.85] years; p = 0.005). There was a female association with AMLs (p < 0.001).

Echogenic nonshadowing renal lesions larger than 4 mm seen at ultrasound should not be assumed to represent an AML without follow-up because a percentage of renal cell carcinomas will be missed. Although certain ultrasound features can be useful in differentiating an AML from a renal cell carcinoma and CT is frequently diagnostic, an understanding of MRI is important because it can potentially detect lipid-poor AMLs.

AJR. American journal of roentgenology. 2017 Aug 23 [Epub ahead of print]

Suresh de Silva, Ross Copping, David Malouf, Anthony Hutton, Fiona Maclean, Peter Aslan

1 Department of Medicine, Sutherland Hospital, Caringbah, Sydney, New South Wales 2229, Australia., 3 Department of Radiology, John Hunter Hospital, New Lambton Heights, New South Wales, Australia., 4 Department of Urology, St. George Hospital, Kogarah, New South Wales, Australia., 5 Waratah Private Hospital, Hurstville, New South Wales, Australia., 6 Douglass Hanly Moir Pathology, Macquarie University, Macquarie Park, New South Wales, Australia.