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nal x-rays reveal this fat in <10 per cent of the patients who subsequently are shown to have fatty tumors. 5 Computerized tomography appears to be more sensitive for the detection of fat but for small intrarenal masses computerized tomography criteria may be indeterminant. 6 Therefore, a confirmatory ultrasound examination should be done, since ultrasound can easily distinguish between the echo-free fluid of a renal cyst and the high level echoes of intrarenal fat. Because the therapy for patients with benign angiomyolipomas is different from that of renal malignancies or renal cysts it is important to make an early identification of this tumor. The urological surgeon may then excise the angiomyolipoma and preserve the kidney. A renal mass with a cluster of high level dense echoes on ultrasound occurring within a region of low attenuation coefficient on computerized tomography should strongly suggest the diagnosis of angiomyolipoma. REFERENCES
1. Farrow, G. M., Harrison, E. G., Jr. and Utz, D. C.: Renal angiomyolipoma: a clinicopathologic study of32 cases. Cancer, 22: 564, 1968.
2. Lee, T. G., Henderson, S. C., Freeny, P. C., Raskin, M. M., Benson, E. P. and Pearse, H. D.: Ultrasonic diagnosis of renal angiomyolipoma. Ultrasound Med., 4: 203, 1978. 3. Duffy, P., Ryan, J. and Aldous, W.: Ultrasound demonstration of a 1.5 cm. intrarenal angiomyolipoma. J. Clin. Ultrasound, 5: 111, 1977. 4. Pickering, R. S., Hattery, R. R., Hartman, G. W. and Holley, K. E.: Computerized tomography of the excised kidney. Radiology, 113: 643, 1974. 5. Medley, B. E., McLeod, R. A. and Houser, 0. W.: Tuberous sclerosis. Semin. Roentgen., 11: 35, 1976. 6. Hattery, R.R., Williamson, B., Stephens, D. H., Sheedy, P. F. and Hartman, G. W.: Computed tomography of renal abnormalities. Rad. Clin. N. Amer., 15: 401, 1977. malities. Rad. Clin. N. Amer., 15: 401, 1977. EDITORIAL COMMENT Retrospective analysis has shown that there are typical sonographic and computerized tomographic appearances for angiomyolipoma. This theoretical ability to diagnose angiomyolipoma preoperatively has now been put into practice. R .C .S.