ULTRASOUND FINDINGS OF RENAL ANGIOMY OLIPOMA by Timothy G. Lee, MD; Sidney C. Henderson, MD; Patrick C. Freeny, MD; Michael M. Raskin, MD; Eric P. Benson, MD; and Harper D. Pearse, MD
ABSTRACT Angiomyolipoma (AML) is a benign renal neoplasm. Preoperative diagnosis is important because of the different surgical approaches t o benign and malignant tumors. Angiographic findings of AML and renal carcinoma may be similar and differentiation difficult. B-mode ultrasound examination of AML demonstrates a different image pattern which may be helpful in differentiation.
Indexing Words Kidney Tuberous Sclerosis
Angiomyolipoma Hypernephroma
Renal angiomyolipoma (AML) is a form of hamartoma, an abnormal development of tissue natural t o the organ (1). 40% to 80% are found in patients with tuberous sclerosis (1-3). Therefore, large solitary angiomyolipomas in patients without tuberous sclerosis as a clinical clue can be a diagnostic problem. This report describes seven cases of renal angiomyolipomas studied with B-mode ultrasound. The ultrasonographic findings differ from those of renal cell carcinoma, showing a cluster of dense internal echoes at low gain. None of these seven patients had any clinical evidence of tuberous sclerosis. DISCUSSION
The angiographic findings in renal AML have been described by many authors ( 3 , 5-8). Although some have reported characteristic angiographic changes ( 5 , 6), it is generally agreed that the findings may be difficult to differentiate from those of renal cell carcinoma (9). Clark believed a specific angiographic appearance t o be the exception ( 3 ) . Becker, in a review of 34 cases (10), concluded that angiography is not a definitive diagnostic procedure. Techniques of B mode ultrasonic scanning (11) and criteria for differentiation of cystic from solid masses (12-14) have been described. Recent experience indicates a diagnostic accuracy of 95%. However, differentiation among types of solid renal tumors remains difficult. For reprints c o n t a c t Timothy G . Lee. MD. Department of Radiology. University of Utah Salt Lake City. UT 84132. 1.50
Hamartoma Ultrasound
Renal parenchyma appears echo-free at low gain settings. A dense central cluster of echoes represents the collecting system. Solid renal masses, such as renal cell carcinoma, are also relatively sonolucent at low gain, but may produce random internal echoes at high gain (16). Maklad et al, reported echogenic tumors which are hypervascular, necrotic or with hemorrhage (17). However, renal angiomyolipomas produce a cluster of internal echoes a t both low and high gain. This feature was present in all of our cases and should be useful in differentiating AML from renal cell carcinoma. It has been suggested that this prominent echo pattern a t low gain is due t o the high fat content and disorganized structure of the tumor (18). Stanley reported a similar ultrasound finding in a case of cavernous hemangioma (19). In our sixth case, the original histological diagnosis was AML. However, another source consulted felt this represented a proximal tubular adenoma or “oncocytoma,” a rare renal tumor of epithelial origin (20). While these two uncommon tumors must, therefore, be included in the differential diagnosis, the fact that the echo pattern of AML is different from renal cell carcinoma is not altered. Evaluation of renal masses by excretory urogra.phy, angiography, and B mode ultrasonic scanning may help identify renal angiomyolipomas preoperatively (21). This is important for several reasons. McCullough states that frequently these lesions have been misdiagnosed JCU. Vol. 6, 143-214 (1978).0 1978. J o h n Wiley a n d Sons, Inc., 0091-2751/78/0006-0150 $01.00,
F I G U R E 3. A ) Ultrasound shows both kidneys in cross section with a cluster of internal echoes on the right side (arrows). Note that a t low gain used on this scan, the renal parenchyma remains sonolucent on the left.
microscopically as sarcomas (22). It is generally agreed that angiomyolipomas are hamartomatous errors of development and are not likely t o undergo malignant degeneration (1). A high index of suspicion of AML provided by careful preoperative diagnostic evaluation should aid the pathologist in his study of the biopsy specimen. If preoperative differentiation can be made between renal cell carcinoma and AML, the surgical approach may be different. McCullough, Walker and McQueeny (21-23) have performed local resections of angiomyolipomas and advocate conservative surgical management. CASE REPORTS*
Patient 1 V.M., a 29 year old female had an excretory urogram because of recurrent urinary tract infections. The urogram suggested a mass in the lower pole of the right kidney (Fig. 1A). Ultrasound showed a cluster of internal echoes and angiography showed characteristic microaneurysms (Figs. 1 B and 1C). A preoperative diagnosis of a solitary right renal angiomyolipoma was made. Because of the pre-operative diagnosis, the patient was spared a radical nephrectomy and had an uncomplicated right heminephrectomy. The diagnosis was confirmed by pathologic examination. Patient 2 B.C., a 61 year old female with a history of recurrent urinary tract infections; excretory urography revealed a mass in the lateral aspect of the left kidney (Fig. 2A). After ultrasonography showed a solid mass with a cluster of *Patients were examined with standard commercially available B mode equipment using 2.25 M H z transducers. 152
F I G U R E 4. A ) A sagittal scan of the left kidney shows a cluster of internal echoes (arrows). The L at the top of the illustration indicates the scan was done on low gain. B ) The cross sectional scan shows a similar cluster of echoes (arrows)
internal echoes (Fig. 2B), and computed axial tomography revealed a fatty mass (Fig. 2C), surgery was performed. The histological diagnosis was angiomyolipoma. Patient 3 O.K., a 35 year old female with a history of a right flank mass found on physical examination. Ultrasound revealed a lower pole renal mass on the right with a cluster of echoes a t low gain (Fig. 3A). At surgery, an encapsulated 15.5 x 14.5 x 9.2 cm mass of the lower pole of the right kidney was removed. This proved t o be an angiomyolipoma. Patient 4 M.R., a ' 7 2 year old female was evaluated for hypertension. The intravenous pyelogram demonstrated a 3 x 4 cm mass in the right kidney. At arteriography a second mass was found in the left kidney. The findings were thought to J O U R N A L O F CLINICAL U L T R A S O U N D
FIGURE 5. A ) A selected film from an excretory urogram shows a large mass in the lower pole of the right kidney which is less dense than the opposite kidney suggesting that the tumor contains fat. 13)A t ultrasound the mass is solid and contains a cluster of internal echoes at low gain (arrows). C) Similar find-
ings are seen in cross section in the right kidney (arrows). A normal kidney i s seen on the left (K) D) Angiography does not show the diagnostic findings of angiomyolipoma.
be compatible with either renal cell carcinomas or angiomyolipomas. Ultrasonically , the masses were solid with a cluster of internal echoes at low gain (Fig. 4A, B). In our experience, this finding is characteristic of AML. Because of the bilateral nature of the tumor the patient was followed until cholecystectomy two years later. At this time a biopsy of the renal tumors was done and the histological diagnosis of AML was confirmed.
suggested perinephric abscess. An abdominal x ray showed findings compat,ible with this impression and an intravenous pyelogram showed a right renal mass (Fig. 5A). By ultrasound the mass was solid with a cluster of echoes at low gain (Fig. 5B, c). Angiography showed an avascular mass (Fig. 5D). As with the previous cases, the ultrasound findings are characteristic of angiomyolipoma. At surgery this was confirmed.
Patient 5 F.B., a 53 year old female who presented with severe abdominal pain, the features of which
Patient 6 R.S., a 15 year old male with idiopathic neurogenic bladder, found to have a large right renal
VOLUME 6 . NUMBER 3
153
FIGURE 6 . A ) A selected f i l m f r o m an excretory urogram shows a mass effect in the lower pole o f the right kidney distorting the collecting system. B) A sagittal ultrasound scan shows t h e solid lower pole mass w i t h a chdracteristic cluster of internal echoes at a l o w gain setting, CI A f i l m f r o m the arterial phase o f an angiogram shows a hypervascular t u m o r thought t o represent an angiomyolipoma.
mass by excretory urography (Fig. 6A). Ultrasound showed the lesion t o be solid with a cluster of dense internal echoes at low gain (Fig. 6B). The possibility of angiomyolipoma was raised. Angiography was consistent with AML (Fig. 6C, D) and a right lower pole heminephrectomy was performed. At the time of discharge, the tumor was thought t o be an angiomyolipoma by all modalities. A subsequent microscopic review has suggested the diagnosis of oncocytoma, a rare renal tumor of epithelial origin. Nonetheless, the patient remains clinically well and we feel that the echo pattern is different from that of renal cell carcinoma. In this case, the patient was spared radical surgery. Patient 7 M.M., a 7 5 year old female who presented with hematuria. An intravenous pyelogram showed bilateral renal masses. Angiographically , findings were consistent with angiomyolipoma. Ultra154
sound showed a cluster of echoes in the tumor at low gain (Fig. 7A, B). Since surgery was not indicated, the patient was followed clinically. After six years there has been no change in the appearance of the renal masses and the diagnosis of AML is felt t o be correct. SUMMARY
The difficulty and importance of a preoperative diagnosis of renal angiomyolipoma have been discussed. With angiography it is not always possible t o discriminate accurately between angiomyolipoma and renal cell carcinoma. In the seven cases reported, angiomyolipomas J O U R N A L O F CLINICAL U L T R A S O U N D
6. 7. 8.
9.
10. 11. 12.
13. 14. 15. FIGURE 7. A ) A sagittal scan of the right kidney shows a cluster of internal echoes a t low gain in the upper pole (arrows). B ) These echoes are again seen on a cross section of the same
16.
kidney. Similar findings were present on the opposite side.
present a characteristic ultrasound appearance. At low gain, carcinomas are relatively sonolucent or may contain random echoes. In contrast, angiomyolipomas show a cluster of internal echoes. This feature, combined with clinical and angiographic findings, may help establish the preoperative diagnosis. REFERENCES
1. Klapproth JJ, Poutasse EF, Hazard JB: Renal angiomyolipomas: report of four cases. AMA Arch Path 67: 400-411, 1959. 2. Moolton SE: Hamartial nature of tuberous sclerosis complex and its bearing on tumor problem: report of case with tumor anomaly of kidney and adenoma sebaceum. Arch Int Med 69: 589-623,1942. 3. Viamonte M Jr, Ravel R, Politano V, Bridges B: Angiographic findings in a patient with tuberous sclerosis. Am J Roentgenol 98: 723-733, 1966. 4. Clark RE, Palubinskas AJ: The angiographic spectrum or renal hamartoma. Am J Roentgenol 114: 715-721,1972. 5. Kihlnani M, Abrams R , Beranbaum E: Angiographic VOLUME 6 , NUMBER 3
17.
18.
features of hamartoma of the kidney: A case report. Radiology 90: 999-1000, 1968. Love L, Frank SJ: Angiographic features of angiomyolipoma of the kidney. Am J Roentgenol 95: 406-408,1965. Palmisano PJ: Renal Hamartoma (angiomyolipoma). Radiology 88: 249-252,1967. Vusko JS, Brochman SK, Bomar RL: Renal angiomyolipoma: A rare cause of spontaneous massive retroperitoneal hemorrhage. Ann Surg 161: 577581,1965. Becker JA, Kinkhabwala M, Pollach H, Bosniak M: Angiomyolipoma (Hamartoma) of the kidney: An angiographic review. Acta Radio (Diag.) 14: 561567,1973. Freimanis AK, Asher SM: Development of diagnostic criteria in echographic study of abdominal lesions. Am J Roentgenol 108: 747-755, 1970. Goldberg BB, Ostrum BJ, Isard HJ: Nephrosonography : Ultrasound differentiation of renal masses. Radiology 90: 1113-1118,1968. Leopold GR, Talner LB, Asher WM, Gosink BB, Gittes R F : Renal ultrasonography: An updated approach to the diagnosis of renal cyst. Radiology 109: 671,1973. Schreck WR, Holmes JH: Ultrasound as a diagnostic aid for rena!. neoplasms and cysts. J Urol 103: 281-285,1970. King DI: Renal Ultrasonography. An aid in the clinical evaluation of renal masses. Radiology 105: 633-640,1972. Ashler WM, Leopold GR: A streamlined diagnostic approach t o renal mass lesions with renal echogram. J Urol 108: 205-208,1972. King DL: Renal ultrasonography. An aid t o the clinical evaluation of renal masses. Radiology 105: 633640, Dec. 1972. Maklad NF, Chuang VP, Doust BD, Cho KJ, Curran JE: Ultrasonic characterization of solid renal lesions: Echographic, angiographic and pathological correlation. Radiology 123: 733-739, 1977. Chilcote WS, Crane D: Renal angiomyolipoma: Ultrasound differentiation. J Clin Ultrasound 2: 226,1974.
19. Stanley R J , Cubillo E, Mancilla-Himenez R, Geisse G, Melson GL: Cavernous hemangioma of the kidney. Am J Roentgenol 125: 682-687,1975. 20. Klein MJ, Valensi QJ: Proximal tubular adenomas of kidney with so-called oncocytic features: A clinicopathologic study of 13 cases of a rarely reported neoplasm. Cancer 38: 906-913, 1976. 21. Walker DE, Barry JM, Hodges CV: Angiomyolipoma: Diagnosis and treatment. J Urol 116: 712-714,1976. 22. McCullough DL, Scott R Jr, Seybold HM: Renal angiomyolipoma (hamartoma) : Review of the literature and report of 7 cases. J Urol 105: 32, 1971. 23. McQueeny AJ, Dahlen GA, Gebhard WF: Cystic hamartoma (angiomyolipoma) of kidney stimulating renal carcinoma. J Urol 92: 98-102, 1964. 155
ABSTRACT Angiomyolipoma (AML) is a benign renal neoplasm. Preoperative diagnosis is important because of the different surgical approaches t o benign and malignant tumors. Angiographic findings of AML and renal carcinoma may be similar and differentiation difficult. B-mode ultrasound examination of AML demonstrates a different image pattern which may be helpful in differentiation.
Indexing Words Kidney Tuberous Sclerosis
Angiomyolipoma Hypernephroma
Renal angiomyolipoma (AML) is a form of hamartoma, an abnormal development of tissue natural t o the organ (1). 40% to 80% are found in patients with tuberous sclerosis (1-3). Therefore, large solitary angiomyolipomas in patients without tuberous sclerosis as a clinical clue can be a diagnostic problem. This report describes seven cases of renal angiomyolipomas studied with B-mode ultrasound. The ultrasonographic findings differ from those of renal cell carcinoma, showing a cluster of dense internal echoes at low gain. None of these seven patients had any clinical evidence of tuberous sclerosis. DISCUSSION
The angiographic findings in renal AML have been described by many authors ( 3 , 5-8). Although some have reported characteristic angiographic changes ( 5 , 6), it is generally agreed that the findings may be difficult to differentiate from those of renal cell carcinoma (9). Clark believed a specific angiographic appearance t o be the exception ( 3 ) . Becker, in a review of 34 cases (10), concluded that angiography is not a definitive diagnostic procedure. Techniques of B mode ultrasonic scanning (11) and criteria for differentiation of cystic from solid masses (12-14) have been described. Recent experience indicates a diagnostic accuracy of 95%. However, differentiation among types of solid renal tumors remains difficult. For reprints c o n t a c t Timothy G . Lee. MD. Department of Radiology. University of Utah Salt Lake City. UT 84132. 1.50
Hamartoma Ultrasound
Renal parenchyma appears echo-free at low gain settings. A dense central cluster of echoes represents the collecting system. Solid renal masses, such as renal cell carcinoma, are also relatively sonolucent at low gain, but may produce random internal echoes at high gain (16). Maklad et al, reported echogenic tumors which are hypervascular, necrotic or with hemorrhage (17). However, renal angiomyolipomas produce a cluster of internal echoes a t both low and high gain. This feature was present in all of our cases and should be useful in differentiating AML from renal cell carcinoma. It has been suggested that this prominent echo pattern a t low gain is due t o the high fat content and disorganized structure of the tumor (18). Stanley reported a similar ultrasound finding in a case of cavernous hemangioma (19). In our sixth case, the original histological diagnosis was AML. However, another source consulted felt this represented a proximal tubular adenoma or “oncocytoma,” a rare renal tumor of epithelial origin (20). While these two uncommon tumors must, therefore, be included in the differential diagnosis, the fact that the echo pattern of AML is different from renal cell carcinoma is not altered. Evaluation of renal masses by excretory urogra.phy, angiography, and B mode ultrasonic scanning may help identify renal angiomyolipomas preoperatively (21). This is important for several reasons. McCullough states that frequently these lesions have been misdiagnosed JCU. Vol. 6, 143-214 (1978).0 1978. J o h n Wiley a n d Sons, Inc., 0091-2751/78/0006-0150 $01.00,
F I G U R E 3. A ) Ultrasound shows both kidneys in cross section with a cluster of internal echoes on the right side (arrows). Note that a t low gain used on this scan, the renal parenchyma remains sonolucent on the left.
microscopically as sarcomas (22). It is generally agreed that angiomyolipomas are hamartomatous errors of development and are not likely t o undergo malignant degeneration (1). A high index of suspicion of AML provided by careful preoperative diagnostic evaluation should aid the pathologist in his study of the biopsy specimen. If preoperative differentiation can be made between renal cell carcinoma and AML, the surgical approach may be different. McCullough, Walker and McQueeny (21-23) have performed local resections of angiomyolipomas and advocate conservative surgical management. CASE REPORTS*
Patient 1 V.M., a 29 year old female had an excretory urogram because of recurrent urinary tract infections. The urogram suggested a mass in the lower pole of the right kidney (Fig. 1A). Ultrasound showed a cluster of internal echoes and angiography showed characteristic microaneurysms (Figs. 1 B and 1C). A preoperative diagnosis of a solitary right renal angiomyolipoma was made. Because of the pre-operative diagnosis, the patient was spared a radical nephrectomy and had an uncomplicated right heminephrectomy. The diagnosis was confirmed by pathologic examination. Patient 2 B.C., a 61 year old female with a history of recurrent urinary tract infections; excretory urography revealed a mass in the lateral aspect of the left kidney (Fig. 2A). After ultrasonography showed a solid mass with a cluster of *Patients were examined with standard commercially available B mode equipment using 2.25 M H z transducers. 152
F I G U R E 4. A ) A sagittal scan of the left kidney shows a cluster of internal echoes (arrows). The L at the top of the illustration indicates the scan was done on low gain. B ) The cross sectional scan shows a similar cluster of echoes (arrows)
internal echoes (Fig. 2B), and computed axial tomography revealed a fatty mass (Fig. 2C), surgery was performed. The histological diagnosis was angiomyolipoma. Patient 3 O.K., a 35 year old female with a history of a right flank mass found on physical examination. Ultrasound revealed a lower pole renal mass on the right with a cluster of echoes a t low gain (Fig. 3A). At surgery, an encapsulated 15.5 x 14.5 x 9.2 cm mass of the lower pole of the right kidney was removed. This proved t o be an angiomyolipoma. Patient 4 M.R., a ' 7 2 year old female was evaluated for hypertension. The intravenous pyelogram demonstrated a 3 x 4 cm mass in the right kidney. At arteriography a second mass was found in the left kidney. The findings were thought to J O U R N A L O F CLINICAL U L T R A S O U N D
FIGURE 5. A ) A selected film from an excretory urogram shows a large mass in the lower pole of the right kidney which is less dense than the opposite kidney suggesting that the tumor contains fat. 13)A t ultrasound the mass is solid and contains a cluster of internal echoes at low gain (arrows). C) Similar find-
ings are seen in cross section in the right kidney (arrows). A normal kidney i s seen on the left (K) D) Angiography does not show the diagnostic findings of angiomyolipoma.
be compatible with either renal cell carcinomas or angiomyolipomas. Ultrasonically , the masses were solid with a cluster of internal echoes at low gain (Fig. 4A, B). In our experience, this finding is characteristic of AML. Because of the bilateral nature of the tumor the patient was followed until cholecystectomy two years later. At this time a biopsy of the renal tumors was done and the histological diagnosis of AML was confirmed.
suggested perinephric abscess. An abdominal x ray showed findings compat,ible with this impression and an intravenous pyelogram showed a right renal mass (Fig. 5A). By ultrasound the mass was solid with a cluster of echoes at low gain (Fig. 5B, c). Angiography showed an avascular mass (Fig. 5D). As with the previous cases, the ultrasound findings are characteristic of angiomyolipoma. At surgery this was confirmed.
Patient 5 F.B., a 53 year old female who presented with severe abdominal pain, the features of which
Patient 6 R.S., a 15 year old male with idiopathic neurogenic bladder, found to have a large right renal
VOLUME 6 . NUMBER 3
153
FIGURE 6 . A ) A selected f i l m f r o m an excretory urogram shows a mass effect in the lower pole o f the right kidney distorting the collecting system. B) A sagittal ultrasound scan shows t h e solid lower pole mass w i t h a chdracteristic cluster of internal echoes at a l o w gain setting, CI A f i l m f r o m the arterial phase o f an angiogram shows a hypervascular t u m o r thought t o represent an angiomyolipoma.
mass by excretory urography (Fig. 6A). Ultrasound showed the lesion t o be solid with a cluster of dense internal echoes at low gain (Fig. 6B). The possibility of angiomyolipoma was raised. Angiography was consistent with AML (Fig. 6C, D) and a right lower pole heminephrectomy was performed. At the time of discharge, the tumor was thought t o be an angiomyolipoma by all modalities. A subsequent microscopic review has suggested the diagnosis of oncocytoma, a rare renal tumor of epithelial origin. Nonetheless, the patient remains clinically well and we feel that the echo pattern is different from that of renal cell carcinoma. In this case, the patient was spared radical surgery. Patient 7 M.M., a 7 5 year old female who presented with hematuria. An intravenous pyelogram showed bilateral renal masses. Angiographically , findings were consistent with angiomyolipoma. Ultra154
sound showed a cluster of echoes in the tumor at low gain (Fig. 7A, B). Since surgery was not indicated, the patient was followed clinically. After six years there has been no change in the appearance of the renal masses and the diagnosis of AML is felt t o be correct. SUMMARY
The difficulty and importance of a preoperative diagnosis of renal angiomyolipoma have been discussed. With angiography it is not always possible t o discriminate accurately between angiomyolipoma and renal cell carcinoma. In the seven cases reported, angiomyolipomas J O U R N A L O F CLINICAL U L T R A S O U N D
6. 7. 8.
9.
10. 11. 12.
13. 14. 15. FIGURE 7. A ) A sagittal scan of the right kidney shows a cluster of internal echoes a t low gain in the upper pole (arrows). B ) These echoes are again seen on a cross section of the same
16.
kidney. Similar findings were present on the opposite side.
present a characteristic ultrasound appearance. At low gain, carcinomas are relatively sonolucent or may contain random echoes. In contrast, angiomyolipomas show a cluster of internal echoes. This feature, combined with clinical and angiographic findings, may help establish the preoperative diagnosis. REFERENCES
1. Klapproth JJ, Poutasse EF, Hazard JB: Renal angiomyolipomas: report of four cases. AMA Arch Path 67: 400-411, 1959. 2. Moolton SE: Hamartial nature of tuberous sclerosis complex and its bearing on tumor problem: report of case with tumor anomaly of kidney and adenoma sebaceum. Arch Int Med 69: 589-623,1942. 3. Viamonte M Jr, Ravel R, Politano V, Bridges B: Angiographic findings in a patient with tuberous sclerosis. Am J Roentgenol 98: 723-733, 1966. 4. Clark RE, Palubinskas AJ: The angiographic spectrum or renal hamartoma. Am J Roentgenol 114: 715-721,1972. 5. Kihlnani M, Abrams R , Beranbaum E: Angiographic VOLUME 6 , NUMBER 3
17.
18.
features of hamartoma of the kidney: A case report. Radiology 90: 999-1000, 1968. Love L, Frank SJ: Angiographic features of angiomyolipoma of the kidney. Am J Roentgenol 95: 406-408,1965. Palmisano PJ: Renal Hamartoma (angiomyolipoma). Radiology 88: 249-252,1967. Vusko JS, Brochman SK, Bomar RL: Renal angiomyolipoma: A rare cause of spontaneous massive retroperitoneal hemorrhage. Ann Surg 161: 577581,1965. Becker JA, Kinkhabwala M, Pollach H, Bosniak M: Angiomyolipoma (Hamartoma) of the kidney: An angiographic review. Acta Radio (Diag.) 14: 561567,1973. Freimanis AK, Asher SM: Development of diagnostic criteria in echographic study of abdominal lesions. Am J Roentgenol 108: 747-755, 1970. Goldberg BB, Ostrum BJ, Isard HJ: Nephrosonography : Ultrasound differentiation of renal masses. Radiology 90: 1113-1118,1968. Leopold GR, Talner LB, Asher WM, Gosink BB, Gittes R F : Renal ultrasonography: An updated approach to the diagnosis of renal cyst. Radiology 109: 671,1973. Schreck WR, Holmes JH: Ultrasound as a diagnostic aid for rena!. neoplasms and cysts. J Urol 103: 281-285,1970. King DI: Renal Ultrasonography. An aid in the clinical evaluation of renal masses. Radiology 105: 633-640,1972. Ashler WM, Leopold GR: A streamlined diagnostic approach t o renal mass lesions with renal echogram. J Urol 108: 205-208,1972. King DL: Renal ultrasonography. An aid t o the clinical evaluation of renal masses. Radiology 105: 633640, Dec. 1972. Maklad NF, Chuang VP, Doust BD, Cho KJ, Curran JE: Ultrasonic characterization of solid renal lesions: Echographic, angiographic and pathological correlation. Radiology 123: 733-739, 1977. Chilcote WS, Crane D: Renal angiomyolipoma: Ultrasound differentiation. J Clin Ultrasound 2: 226,1974.
19. Stanley R J , Cubillo E, Mancilla-Himenez R, Geisse G, Melson GL: Cavernous hemangioma of the kidney. Am J Roentgenol 125: 682-687,1975. 20. Klein MJ, Valensi QJ: Proximal tubular adenomas of kidney with so-called oncocytic features: A clinicopathologic study of 13 cases of a rarely reported neoplasm. Cancer 38: 906-913, 1976. 21. Walker DE, Barry JM, Hodges CV: Angiomyolipoma: Diagnosis and treatment. J Urol 116: 712-714,1976. 22. McCullough DL, Scott R Jr, Seybold HM: Renal angiomyolipoma (hamartoma) : Review of the literature and report of 7 cases. J Urol 105: 32, 1971. 23. McQueeny AJ, Dahlen GA, Gebhard WF: Cystic hamartoma (angiomyolipoma) of kidney stimulating renal carcinoma. J Urol 92: 98-102, 1964. 155
