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Problems in Interpretation of Angiograms in Renal Mass Lesions
THE JOURNAL OF UROLOGY
Copyright © 1972 by The Williams & Wilkins Co.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS IN RENAL MASS LESIONS JAY M. YOUNG*
AND
JAMES W. MORROW
From the Los Angeles County-University of Southern California, Los Angeles, California
The findings on 99 selective renal angiograms performed during the last 3 years for evaluation of renal mass lesions have been studied. The advantages and difficulties encountered with the interpretation of renal angiograms in solving clinical problems related to the diagnosis and treatment of renal mass lesions are discussed. Selective angiography is an invaluable tool in the evaluation of tumor deformities of the kidney. At this institution, selective renal angiography is used to evaluate most mass lesions of the kidney. There were sufficient angiographic data in 99 cases to diagnose 20 renal carcinomas, 60 renal cysts, 2 perinephric hematomas, 1 pyohydronephrosis, 1 perinephric abscess and 1 case of renal tuberculosis (table 1). In 8 of the 99 cases a specific angiographic diagnosis could not be made. The operative findings in these 8 cases were 2 carcinomas, 2 tuberculous abscesses, l renal carbuncle, 1 perinephric abscess and 2 renal cysts. In 6 of the 99 cases the angiographic findings did not correlate with the findings at operation. Thus, there were 14 of the 99 cases (14 per cent) in which no angiographic diagnosis could be made or in which the operative findings did not corroborate with the angiographic diagnosis that was made (table 2). Ten of the 14 diagnostic problems manifested an a vascular pattern angiographically. In this group there were 3 carcinomas, 3 cysts, 1 renal carbuncle, 2 tuberculous abscesses and 1 perinephric abscess. DISCUSSION
Selective renal angiography is reported to be 95 to 99 per cent accurate in the differentiation of hypernephromas and renal cysts. 1• 2 The consensus is that renal angiography is an essential study in the evaluation of renal masses. However, in this series the interpretation of renal angiograms provided incorrect ui.~s;,1v,,c,~ multiple diagnoses or no diagnosis in 14 per cent of the cases (14 of 99 cases). Since 33 of 60 angiographically diagnosed cysts were not explored or aspirated, it is possible that the over-all angiographic diagnostic error could be greater than Accepted for publica,tion June 25, 1971. Read at annual meeting of Western Section, American Urological Association, Las Vegas, Nevada, April 25-30, Hl71. * Current address: 31582 South Coast Highway, South Laguna, California 92677. 1 Halpern, J\I[.: Renal-cell carcinoma. New Engl. J. Med., 270: 108, 1964, 2 Folin, J.: Angiography in renal tumours. Its value in diagnosis and differential diagnosis as a complement to conventional methods. Acta Radio!., suppl. 267, p. 7, 1967,
14 per cent. The problems that arise for the clinician are those cases in which no angiographic interpretato tion is possible or in avascular masses that be benign serous cysts. When these diagnostic mas arise m patients who are marginal risks, a value judgment regarding operative intervention must be made by the clinician. Avascular carcinomas simulating benign cysts. The most important diagnostic errors involve the avascular renal carcinomas which are interpreted as benign cysts and thus remain as viable undiagnosed cancers. Three such cases were found in this (cases 7, 8 and 9). Case 9 was a 16-year-old black male youth who sustained a stab wound to the lower abdomen. He manifested no hematuria or other urological complaint. An excretory urogram (IVP) revealed a tumor deformity of the right kidney, Because of the stab wound the patient was taken to the operating room on an emergency priority for exploration of the abdomen. Postoperatively, a selective renal arteriogram showed a benign renal cyst (fig. 1). Because of the patient's age, increased risk of trauma to a cyst-laden kidney and uneasiness about the nature of the lesion, surgical was advised. At the time of operation, nephrectomy followed the open aspiration of bloody necrotic debris from the renal mass. A hypernephroma with renaI vein involvement was removed. Percutaneous as, piration of the two other angiographically diagnosed cysts led directly to exploration. In case 7 the gram was interpreted as a cyst (fig. 2, A). A mass was noted on percutaneous puncture (fig, 2, In case 8 a bloody tap was observed. V asculitis and neovascularity. Early in the series a 44-year-old white man presented with matic gross hematuria (case 12). The patient TABLE
1. Angiographic diagnoses which were confirmed clinically or histologically, 85 cases 20
Diagnosis of tumor: Corroborated by surgical findings Corroborated by post mortem findings Corroborated by metastatic findings
16 3* I
Diagnosis of cyst: Corroborated by aspiration Corroborated by operation No further diagnostic or therapeutic procedures
23 4 33
Diagnosis of other renal mass lesions: Perinephric hematomas Pyohydronephrosis Tuberculosis Perinephric abscess
* 1 case was bilateral.
925
60
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YOUNG AND MORROW
2. Cases in which no angiographic diagnosis was made or in which the surgical findings did not correlate with the angiographic diagnosis
TABLE
Case/Pt./ Hosp. No.
Angiographic Diagnosis
1/HM/308-04-84 No definitive diagnosis; could not rule out tumor 2/DG/295-23-44 Avascul~r mass without tumor vessels; no definitive diagnosis 3/AA/285-02-58 No definitive diagnosis; hydronephrosis of lower poie, possible cold abscess or hematoma 4/MB/201-06-28 Avascular mass attached to kidney with perinephric inflammatory vessels 5/CK/275-41-68 A vascular neoplasm or organized hematoma 6/BM/285-41-05 Inflammatory process with secondary association of kidney 7/MR/266-02-07 Renal cyst 8/HW/294-35-19 Renal cyst 9/MC/151-20-16 Renal cyst 10/MC/260-36-62 Ca of kidney 11/IB/244-92-12 Neovascularity 12/FD/295-26-35 Ca of left kidney with multiple aneurysms
13/EF /032-40-68 14/CA/165-64-55
Infection versus tumor Renal mass; cannot rule out Ca
Operative Finding
perienced renal trauma 2 years prior to this hospitalization. During the present admission a diagnosis of renal carcinoma was made angiographically and nephrectomy was performed (fig. 3). A diffuse vasculitis with no evidence of renal tumor was noted in the operative specimen. It is the impression that
Renal carbuncle Papillary adenocarcinoma Tuberculosis
Perinephric abscess Hemato ma in cyst Squamous cell Ca
Renal cell Ca Renal cell Ca Renal cell Ca Cyst Renal cell Ca Subacute and chronic vasculitis, m ultifocal proliferative glomerulonephritis, focal acute and chronic pyelonephritis Inflammatory cyst Tuberculosis
Fm. 1. Case 9. Angiogram of avascular hypernephroma simulating benign renal cyst.
Fm. 2. Case 7. A, angiogram of a vascular hypernephroma simulating benign renal cyst. B, percutaneous needle puncture and instillation of hypaque into solid renal mass which simulated a cyst angiographically.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS
angiography in acute renal injury and after subsequent healing has shown this picture of vasculitis simulating tumor vessels. 3 In case 11 an area of neovascularity similar to that observed in case 12 was described (fig. 4). However, it was not considered to represent a hypernephroma. A renal cell carcinoma was removed at operation. Infected cysts. Secondary infected cysts were diagnosed at operation in cases 5, 10 and 13. No definitive angiographic diagnoses were offered in cases 5 and 13. In case 10 the angiogram was interpreted as a carcinoma while at operation a cyst was noted (fig. 5). Case 5 was reported as an a vascular neoplasm or an organized hematoma (fig. 6, A). The percutaneous needle aspiration returned blood (fig. 6, B). A hematoma in a renal cyst was noted at operation. Tuberculosis. Renal tuberculosis may simulate a vascular neoplasms. 4 Cases 3 and 14 were diagnosed angiographically as a vascular masses in which tumor could not be ruled out (fig. 7). In these cases the classic findings of cavitation with shortened and blocked small arterial branches were absent. 5 Papillary adenocarcinoma. Papillary adenocarcinoma, as noted in case 2, represents 5 per cent of renal neoplasms (fig. 8). This tumor characteristically has an angiographic picture of avascularity. 6 It may thus simulate a renal cyst. The angiogram in this case afforded no definitive diagnosis other than avascular mass. Inflammatory processes. In case 4 a 64-year-old white woman with diabetes mellitus had a 40-pound weight malaise and anemia (fig. 9). The weight loss had progressed during the 6-month period prior to hospitalization. A left flank mass extended from the costal margin to the iliac crest. The mass was non-tender, smooth and well delineated. The renal angiogram was interpreted to be an avascular mass attached to the left kidney with perinephric inflammatory vessels. The clinical course justified the inclusion of a neoplasm in the differential diagnosis. During the subsequent operative dissection of the mass, an abscess cavity was entered and approximately 1 L of purulent liquid was evacuated. In case 1 a 49-year-old black male diabetic was evaluated for fever of undetermined origin. A renal mass was noted on the IVP. No definitive diagnosis could be made angiographically. A renal carbuncle was noted at operation. In case 6 a 62-year-old white woman was evaluated for intermittent fever and right flank pain 6 months in duration. The angiogrnm was interpreted as an inflammatory process with secondary involvement Halpern, M.: Personal communication. Becker, J. A., Fleming, R., Kanter, I. and Melicow, M.: Misleading appearances in renal angiography. Radiology, 88: 691, 1967. 5 Frimann-Dahl, J.: Selective angiography in renal tuberculosis. Acta Radio!., 49: 31, 1958. 6 Weiss, R. M., Becker, J. A., Davidson, A. J. and Lytton, B.: Angiogrnphic appearance of renal papillary-tubular adenocarcinomas. J. Urol., 102: 661,
FIG. 3. Case 12. Angiogram of renal mass simulating hypernephroma. Acute and chronic vasculitis was noted on pathologic examination without evidence of tumor.
3
4
1969.
Fm. 4. Case 11. Angiogram of intrarenal mass interpreted as area of neovascularity. Hyperncphromfi, was removed at operation. of the kidney. On gross inspection at operation the kidney was considered to represent an of xanthogranulomatous pyelonephritis.
928
YOUNG AND MORROW
Fw. 5. Case 10. Angiogram of renal cyst with inflammatory vessels simulating avascular carcinoma
Fw. 6. Case 5. A, angiogram interpreted as avascular neoplasm or organized hematoma. B, percutaneous needle aspiration revealed blood. Hematoma in renal cyst was noted at operation.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS
Fm. 7. Case 14. Renal tuberculosis simulating avascular carcinoma.
929
Fm. 8. Case 2. No definitive diagnosis was made angiographically. Papillary adenocarcinoma was removed.
Fm. 9. Case 1. Avascular mass attached to kidney noted to be perinephric abscess at time of operation 0
930
YOUNG AND MORROW
examination indicated the presence of a squamous cell carcinoma arising from the renal pelvis. Lang has recently reviewed 361 cases of renal mass lesions studied angiographically. 7 Operative findings and histologic examinations sustained the angiographic diagnosis in 87 per cent of the cases. This figure is comparable to the current series of 86 per cent correlation. Since, as previously indicated, not all patients in the present study were operated upon, the angiographic diagnosis was not confirmed in all instances. Lang noted that in diseases such as infected cysts, metastatic carcinoma to the kidney, avascular carcinoma and benign renal tumors such as adenomas, fibromas and peripelvic lipomas, the angiographic diagnostic accuracy is lower than that of hypernephroma. 7 The current experience confirms this impression. Other investigators have noted that a vascular carcinomas may lack the characteristic tumor vessels and puddling during the nephrogram phase of angiography.4 They also noted that certain inflammatory lesions, abscesses, tuberculosis and angiomyolipomas can simulate avascular malignant neoplasms of the kidney. 4 • 8 Earlier reports in the literature of 95 to 99 per cent accuracy in the angiographic diagnosis of renal masses do not correlate with the current or Lang's 7 Lang, E. K.: The accuracy of roentgenographic techniques in the diagnosis of renal mass lesions. Radiology, 98: 119, 1971. 8 Meaney, T. F.: Errors in angiographic diagnosis of renal masses. Radiology, 93: 361, 1969.
series. In any large series there are inevitably a few masses which defy angiographic interpretation. It is significant that in 8 of 99 cases no unequivocal angiographic interpretation was possible. This equivocation led directly and immediately to operation. Only 6 per cent of 99 cases in this series were incorrectly diagnosed angiographically. The diagnostic evaluation of renal mass lesions has been improved with the use of the diagnostic cyst puncture. TI1e reader is referred to other articles for information on the technique and diagnostic accuracy of percutaneous renal cyst puncture. 8 • 9 Lang reports 97 per cent accuracy when renal cyst puncture is used in conjunction with selective renal angiography.7 The 3 cases of renal carcinoma in the present series which were diagnosed as cysts angiographically were solid or blood-filled on aspiration. CONCLUSION
Selective renal angiography is essential in the adequate evaluation of renal mass lesions. However, the clinician must be cognizant of the limitation of these studies. Surgical exploration must remain a part of the diagnostic as well as the therapeutic armamentarium of the clinician. Judicious use of percutaneous needle aspiration of renal masses which are suggestive of cyst will likely further reduce the incidence of exploratory operation. 9 Lang, E. K.: The differential diagnosis of renal cysts and tumors. Cyst puncture, aspiration, and analysis of cyst contents for fat as diagnostic criteria for renal cysts. Radiology, 87: 883, 1966.
Copyright © 1972 by The Williams & Wilkins Co.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS IN RENAL MASS LESIONS JAY M. YOUNG*
AND
JAMES W. MORROW
From the Los Angeles County-University of Southern California, Los Angeles, California
The findings on 99 selective renal angiograms performed during the last 3 years for evaluation of renal mass lesions have been studied. The advantages and difficulties encountered with the interpretation of renal angiograms in solving clinical problems related to the diagnosis and treatment of renal mass lesions are discussed. Selective angiography is an invaluable tool in the evaluation of tumor deformities of the kidney. At this institution, selective renal angiography is used to evaluate most mass lesions of the kidney. There were sufficient angiographic data in 99 cases to diagnose 20 renal carcinomas, 60 renal cysts, 2 perinephric hematomas, 1 pyohydronephrosis, 1 perinephric abscess and 1 case of renal tuberculosis (table 1). In 8 of the 99 cases a specific angiographic diagnosis could not be made. The operative findings in these 8 cases were 2 carcinomas, 2 tuberculous abscesses, l renal carbuncle, 1 perinephric abscess and 2 renal cysts. In 6 of the 99 cases the angiographic findings did not correlate with the findings at operation. Thus, there were 14 of the 99 cases (14 per cent) in which no angiographic diagnosis could be made or in which the operative findings did not corroborate with the angiographic diagnosis that was made (table 2). Ten of the 14 diagnostic problems manifested an a vascular pattern angiographically. In this group there were 3 carcinomas, 3 cysts, 1 renal carbuncle, 2 tuberculous abscesses and 1 perinephric abscess. DISCUSSION
Selective renal angiography is reported to be 95 to 99 per cent accurate in the differentiation of hypernephromas and renal cysts. 1• 2 The consensus is that renal angiography is an essential study in the evaluation of renal masses. However, in this series the interpretation of renal angiograms provided incorrect ui.~s;,1v,,c,~ multiple diagnoses or no diagnosis in 14 per cent of the cases (14 of 99 cases). Since 33 of 60 angiographically diagnosed cysts were not explored or aspirated, it is possible that the over-all angiographic diagnostic error could be greater than Accepted for publica,tion June 25, 1971. Read at annual meeting of Western Section, American Urological Association, Las Vegas, Nevada, April 25-30, Hl71. * Current address: 31582 South Coast Highway, South Laguna, California 92677. 1 Halpern, J\I[.: Renal-cell carcinoma. New Engl. J. Med., 270: 108, 1964, 2 Folin, J.: Angiography in renal tumours. Its value in diagnosis and differential diagnosis as a complement to conventional methods. Acta Radio!., suppl. 267, p. 7, 1967,
14 per cent. The problems that arise for the clinician are those cases in which no angiographic interpretato tion is possible or in avascular masses that be benign serous cysts. When these diagnostic mas arise m patients who are marginal risks, a value judgment regarding operative intervention must be made by the clinician. Avascular carcinomas simulating benign cysts. The most important diagnostic errors involve the avascular renal carcinomas which are interpreted as benign cysts and thus remain as viable undiagnosed cancers. Three such cases were found in this (cases 7, 8 and 9). Case 9 was a 16-year-old black male youth who sustained a stab wound to the lower abdomen. He manifested no hematuria or other urological complaint. An excretory urogram (IVP) revealed a tumor deformity of the right kidney, Because of the stab wound the patient was taken to the operating room on an emergency priority for exploration of the abdomen. Postoperatively, a selective renal arteriogram showed a benign renal cyst (fig. 1). Because of the patient's age, increased risk of trauma to a cyst-laden kidney and uneasiness about the nature of the lesion, surgical was advised. At the time of operation, nephrectomy followed the open aspiration of bloody necrotic debris from the renal mass. A hypernephroma with renaI vein involvement was removed. Percutaneous as, piration of the two other angiographically diagnosed cysts led directly to exploration. In case 7 the gram was interpreted as a cyst (fig. 2, A). A mass was noted on percutaneous puncture (fig, 2, In case 8 a bloody tap was observed. V asculitis and neovascularity. Early in the series a 44-year-old white man presented with matic gross hematuria (case 12). The patient TABLE
1. Angiographic diagnoses which were confirmed clinically or histologically, 85 cases 20
Diagnosis of tumor: Corroborated by surgical findings Corroborated by post mortem findings Corroborated by metastatic findings
16 3* I
Diagnosis of cyst: Corroborated by aspiration Corroborated by operation No further diagnostic or therapeutic procedures
23 4 33
Diagnosis of other renal mass lesions: Perinephric hematomas Pyohydronephrosis Tuberculosis Perinephric abscess
* 1 case was bilateral.
925
60
926
YOUNG AND MORROW
2. Cases in which no angiographic diagnosis was made or in which the surgical findings did not correlate with the angiographic diagnosis
TABLE
Case/Pt./ Hosp. No.
Angiographic Diagnosis
1/HM/308-04-84 No definitive diagnosis; could not rule out tumor 2/DG/295-23-44 Avascul~r mass without tumor vessels; no definitive diagnosis 3/AA/285-02-58 No definitive diagnosis; hydronephrosis of lower poie, possible cold abscess or hematoma 4/MB/201-06-28 Avascular mass attached to kidney with perinephric inflammatory vessels 5/CK/275-41-68 A vascular neoplasm or organized hematoma 6/BM/285-41-05 Inflammatory process with secondary association of kidney 7/MR/266-02-07 Renal cyst 8/HW/294-35-19 Renal cyst 9/MC/151-20-16 Renal cyst 10/MC/260-36-62 Ca of kidney 11/IB/244-92-12 Neovascularity 12/FD/295-26-35 Ca of left kidney with multiple aneurysms
13/EF /032-40-68 14/CA/165-64-55
Infection versus tumor Renal mass; cannot rule out Ca
Operative Finding
perienced renal trauma 2 years prior to this hospitalization. During the present admission a diagnosis of renal carcinoma was made angiographically and nephrectomy was performed (fig. 3). A diffuse vasculitis with no evidence of renal tumor was noted in the operative specimen. It is the impression that
Renal carbuncle Papillary adenocarcinoma Tuberculosis
Perinephric abscess Hemato ma in cyst Squamous cell Ca
Renal cell Ca Renal cell Ca Renal cell Ca Cyst Renal cell Ca Subacute and chronic vasculitis, m ultifocal proliferative glomerulonephritis, focal acute and chronic pyelonephritis Inflammatory cyst Tuberculosis
Fm. 1. Case 9. Angiogram of avascular hypernephroma simulating benign renal cyst.
Fm. 2. Case 7. A, angiogram of a vascular hypernephroma simulating benign renal cyst. B, percutaneous needle puncture and instillation of hypaque into solid renal mass which simulated a cyst angiographically.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS
angiography in acute renal injury and after subsequent healing has shown this picture of vasculitis simulating tumor vessels. 3 In case 11 an area of neovascularity similar to that observed in case 12 was described (fig. 4). However, it was not considered to represent a hypernephroma. A renal cell carcinoma was removed at operation. Infected cysts. Secondary infected cysts were diagnosed at operation in cases 5, 10 and 13. No definitive angiographic diagnoses were offered in cases 5 and 13. In case 10 the angiogram was interpreted as a carcinoma while at operation a cyst was noted (fig. 5). Case 5 was reported as an a vascular neoplasm or an organized hematoma (fig. 6, A). The percutaneous needle aspiration returned blood (fig. 6, B). A hematoma in a renal cyst was noted at operation. Tuberculosis. Renal tuberculosis may simulate a vascular neoplasms. 4 Cases 3 and 14 were diagnosed angiographically as a vascular masses in which tumor could not be ruled out (fig. 7). In these cases the classic findings of cavitation with shortened and blocked small arterial branches were absent. 5 Papillary adenocarcinoma. Papillary adenocarcinoma, as noted in case 2, represents 5 per cent of renal neoplasms (fig. 8). This tumor characteristically has an angiographic picture of avascularity. 6 It may thus simulate a renal cyst. The angiogram in this case afforded no definitive diagnosis other than avascular mass. Inflammatory processes. In case 4 a 64-year-old white woman with diabetes mellitus had a 40-pound weight malaise and anemia (fig. 9). The weight loss had progressed during the 6-month period prior to hospitalization. A left flank mass extended from the costal margin to the iliac crest. The mass was non-tender, smooth and well delineated. The renal angiogram was interpreted to be an avascular mass attached to the left kidney with perinephric inflammatory vessels. The clinical course justified the inclusion of a neoplasm in the differential diagnosis. During the subsequent operative dissection of the mass, an abscess cavity was entered and approximately 1 L of purulent liquid was evacuated. In case 1 a 49-year-old black male diabetic was evaluated for fever of undetermined origin. A renal mass was noted on the IVP. No definitive diagnosis could be made angiographically. A renal carbuncle was noted at operation. In case 6 a 62-year-old white woman was evaluated for intermittent fever and right flank pain 6 months in duration. The angiogrnm was interpreted as an inflammatory process with secondary involvement Halpern, M.: Personal communication. Becker, J. A., Fleming, R., Kanter, I. and Melicow, M.: Misleading appearances in renal angiography. Radiology, 88: 691, 1967. 5 Frimann-Dahl, J.: Selective angiography in renal tuberculosis. Acta Radio!., 49: 31, 1958. 6 Weiss, R. M., Becker, J. A., Davidson, A. J. and Lytton, B.: Angiogrnphic appearance of renal papillary-tubular adenocarcinomas. J. Urol., 102: 661,
FIG. 3. Case 12. Angiogram of renal mass simulating hypernephroma. Acute and chronic vasculitis was noted on pathologic examination without evidence of tumor.
3
4
1969.
Fm. 4. Case 11. Angiogram of intrarenal mass interpreted as area of neovascularity. Hyperncphromfi, was removed at operation. of the kidney. On gross inspection at operation the kidney was considered to represent an of xanthogranulomatous pyelonephritis.
928
YOUNG AND MORROW
Fw. 5. Case 10. Angiogram of renal cyst with inflammatory vessels simulating avascular carcinoma
Fw. 6. Case 5. A, angiogram interpreted as avascular neoplasm or organized hematoma. B, percutaneous needle aspiration revealed blood. Hematoma in renal cyst was noted at operation.
PROBLEMS IN INTERPRETATION OF ANGIOGRAMS
Fm. 7. Case 14. Renal tuberculosis simulating avascular carcinoma.
929
Fm. 8. Case 2. No definitive diagnosis was made angiographically. Papillary adenocarcinoma was removed.
Fm. 9. Case 1. Avascular mass attached to kidney noted to be perinephric abscess at time of operation 0
930
YOUNG AND MORROW
examination indicated the presence of a squamous cell carcinoma arising from the renal pelvis. Lang has recently reviewed 361 cases of renal mass lesions studied angiographically. 7 Operative findings and histologic examinations sustained the angiographic diagnosis in 87 per cent of the cases. This figure is comparable to the current series of 86 per cent correlation. Since, as previously indicated, not all patients in the present study were operated upon, the angiographic diagnosis was not confirmed in all instances. Lang noted that in diseases such as infected cysts, metastatic carcinoma to the kidney, avascular carcinoma and benign renal tumors such as adenomas, fibromas and peripelvic lipomas, the angiographic diagnostic accuracy is lower than that of hypernephroma. 7 The current experience confirms this impression. Other investigators have noted that a vascular carcinomas may lack the characteristic tumor vessels and puddling during the nephrogram phase of angiography.4 They also noted that certain inflammatory lesions, abscesses, tuberculosis and angiomyolipomas can simulate avascular malignant neoplasms of the kidney. 4 • 8 Earlier reports in the literature of 95 to 99 per cent accuracy in the angiographic diagnosis of renal masses do not correlate with the current or Lang's 7 Lang, E. K.: The accuracy of roentgenographic techniques in the diagnosis of renal mass lesions. Radiology, 98: 119, 1971. 8 Meaney, T. F.: Errors in angiographic diagnosis of renal masses. Radiology, 93: 361, 1969.
series. In any large series there are inevitably a few masses which defy angiographic interpretation. It is significant that in 8 of 99 cases no unequivocal angiographic interpretation was possible. This equivocation led directly and immediately to operation. Only 6 per cent of 99 cases in this series were incorrectly diagnosed angiographically. The diagnostic evaluation of renal mass lesions has been improved with the use of the diagnostic cyst puncture. TI1e reader is referred to other articles for information on the technique and diagnostic accuracy of percutaneous renal cyst puncture. 8 • 9 Lang reports 97 per cent accuracy when renal cyst puncture is used in conjunction with selective renal angiography.7 The 3 cases of renal carcinoma in the present series which were diagnosed as cysts angiographically were solid or blood-filled on aspiration. CONCLUSION
Selective renal angiography is essential in the adequate evaluation of renal mass lesions. However, the clinician must be cognizant of the limitation of these studies. Surgical exploration must remain a part of the diagnostic as well as the therapeutic armamentarium of the clinician. Judicious use of percutaneous needle aspiration of renal masses which are suggestive of cyst will likely further reduce the incidence of exploratory operation. 9 Lang, E. K.: The differential diagnosis of renal cysts and tumors. Cyst puncture, aspiration, and analysis of cyst contents for fat as diagnostic criteria for renal cysts. Radiology, 87: 883, 1966.