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Changing Concepts in the Diagnosis and Management of Renal Cysts
Vol. 111, March
THE JOURNAL OF UROLOGY
Copyright © 1974 by The Williams & Wilkins Co.
Printed in U.S.A.
CHANGING CONCEPTS IN THE DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS HOWARD M. POLLACK, BARRY B. GOLDBERG AND MORTON BOGASH From the Departments of Radiology and Urology, Episcopal Hospital and Temple University Health Sciences Center, Philadelphia, Pennsylvania
Renal cysts occur frequently, especially in elderly subjects. Often asymptomatic, they are far more common than tumors and probably outnumber all other renal masses combined. 1 Cysts are generally indistinguishable from tumors on excretory urography (IVP). Therefore, a battery of studies is used to differentiate the two, including nephrosonography (ultrasound examination), nephrotomography, arteriography and needle puncture. Although the accuracy claimed for such non-surgical methods of investigation has been reported to approach 100 per cent, 2 there are some who still advocate routine surgical exploration of all masses. 3 These investigators believe that only in this way will all tumors be discovered. In view of the prevalence of renal cysts, the philosophy of operating on every renal mass represents a waste of medical resources if the same information may be obtained by non-surgical means. When added to the not-inconsiderable morbidity associated with renal exploration, especially in the elderly, 4 the matter takes on more serious overtones. Therefore, it seems appropriate to review the entire question of the diagnosis of renal cysts.
criterion were applied some tumors might have been misinterpreted as cysts. Nevertheless, we thought that the percentage error within this group would be small and negligible in the entire series. RESULTS
Analysis was made of 109 patients with renal cysts. The number and type of diagnostic examinations performed are listed in table 1. The patients are grouped according to steps, each step representing a succeeding stage of the diagnostic study. After the initial studies of urography and ultrasound only (step 1) the correct diagnosis could be predicted in 89 per cent of the cases with 92 per cent accuracy. The addition of nephrotomography (step 2) allowed the diagnosis to be made in 92 per cent of the patients with 97 per cent accuracy. The addition of cyst puncture and contrast instillation (step 3) made it possible to predict the correct diagnosis in 100 per cent of the cases in which a diagnosis was rendered. The drop-outs between steps 2 and 3 (from 102 to 52 cases) represent those patients in whom cyst puncture was omitted because of patient refusal, size and location of the cyst or the existence of an obvious indication for an operation, precluding the need for further study. The diagnosis in these cases is based on criterion 1 or 3. Of the last 40 renal cysts seen, 33 have been successfully aspirated (82 per cent). All initially incorrect impressions were rectified by the end of step 3. However, in 11 per cent of the group the diagnosis was indeterminate. An operation was recommended in all 12 of these patients and carried out in 10 of them. Renal cysts were present in all. It is noteworthy that during the years encompassed by this study 30 patients with renal tumors were seen. None of these was falsely diagnosed as having a renal cyst.
MATERIAL
The case histories were reviewed of all adults in whom a roentgenographic diagnosis of renal cyst was made between 1968 and 1972. Diagnosis was assumed to be correct if one or more criteria were met: 1) surgical or autopsy proof; 2) radiographic findings typical of cyst, including aspiration and double-contrast studies and 3) other radiographic findings typical of cyst but without cyst aspiration and no change in the size of the mass for 3 or more years. The last criterion only suggests that a neoplasm is not present. Undoubtedly, if only this Accepted for publication July 13, 1973. Read at annual meeting of American Urological Association, New York, New York, May 13-17, 1973. 1 Lalli, A. F.: The direct fluoroscopically guided approach to renal, thoracic and skeletal lesions. In: Current Problems in Radiology. Chicago: Year Book Medical Publishers, Inc., vol. 2, No. 3, 1972. Goldberg, B. B. and Pollack, H. M.: Differentiation of renal masses using A-mode ultrasound. J. Urol., 105:
DISCUSSION
2
765, 1971.
'Leitner, W. A., Anderson, E. E., Weber, C. H., Grimes, J. H. and Johnsrude, I. S.: Limitations of arteriography in renal mass evaluation. Arch. Intern. Med., 130: 868, 1972. 'Kropp, K. A., Grayhack, J. T., Wendel, R. M. and Dahl, D.S.: Morbidity and mortality of renal exploration for cyst. Surg., Gynec. & Obst., 125: 803, 1967. 326
For the last several years our policy in regard to management of renal masses has been, in general, that all pathological renal masses which are not cysts require an operation while, conversely, all those which are cysts do not require operation with the following exceptions: 1) a cyst producing distressing symptoms, usually by virtue of pressure or infection; 2) a cyst producing significant obstruction or otherwise interfering with renal function and 3) all masses thought to be cysts but cannot be conclusively proved radiographically. Clearly, considerable dependence is placed upon
:-l2'7
CHANGING CONCEPTS IN DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS
TABLE
1. Types and accuracy of diagnostic studies in renal cysts Definitive Diagnosis Rendered No.(%)
Rendered Correctly (cyst) No.(%)
Diagnosis Indefinite No. (C:{1)
91 (92)
12 ( 11)
52
97 (89) 94 (92) 48 (92)
91 (97) 48 (100)
8 (8) 4 (8)
13
8 (60)
7 (88)
5 (40)
No. Cases
Step 1 Step 2 Step 3 Step 4
Urography and ultrasound Urography, ultrasound and nephrotomography Urography, ultrasound, nephrotomography and needle puncture Step 2 in conjunction with arteriography
the results of radiographic and sonographic investigation of renal masses, since the outcome of such investigations largely determines whether the patient will be subjected to an operation. Our results indicate that an accurate non-surgical diagnosis of renal cyst is possible in almost all cases, with considerable savings in cost, convenience and safety to the patient (table 2). However, such salutory results require strict adherence to a tightly structured diagnostic protocol (see figure). After a mass was demonstrated by IVP the next study used was nephrosonography. Sonographic patterns in renal masses may be divided into 3 types: 1) the cyst pattern, 2) the solid pattern and 3) the complex pattern. 2 Patients demonstrating a solid pattern were treated as tumor suspects and were studied by arteriography. They will not be discussed further here. Patients with cystic patterns were presumed to have renal cysts, since the likelihood of such an association is approximately 90 per cent. 2 However, this degree of accuracy was considered too low to be clinically acceptable and, in an attempt to improve it further, this group of patients was studied by nephrotomography. This modality, too, is reputed to be approximately 90 per cent accurate in differentiating cysts from tumors, although such precision requires meticulous attention to details of radiographic technique and optimally functioning equipment. In practice, this is difficult to attain consistently, with the result that nephrotomography frequently does not reach its full potential.' Nonetheless, when the classical tomographic findings of renal cyst are clearly demonstrable, the diagnosis may be accepted with the level of confidence cited. These findings include a smooth, pencil-line thin wall visible throughout the protruding portion of the cyst, uniform lucency throughout the cyst and a smooth, sharply contrasted interface at the junction of the cyst and the adjacent renal parenchyma. The presence of a beak or spur at the borders of the cyst-parenchyma junction is not, in our experience, infallible evidence of the presence of a cyst. Patients with typical criteria for renal cysts on 5 Lang, E. K., Johnson, B., Chance, H. L., Enright, J. R., Fontenot, R., Trichel, B. E., Wood, M., Brown, R. and St. Martin, E. C.: Assessment of avascular renal mass lesions: the use of nephrotomography, arteriography, cyst puncture, double contrast study and histochemical and histopathologic examination of the aspirate. Southern Med. J., 65: 1, 1972.
109 102
TABLE
2. Comparison of radiologic versus surgical diagnosis of renal cysts
Diagnostic accuracy Major morbidity Mortality Socioeconomic: Hospital days (av.) Hospital costs (av.) Lost wages (av.)
Radiologic
Surgical
100%*
Approx. 100?0 ;rn?o 4 1.5r;,;1 4
0% 0%
0 .. 1 $1:J0 .. ]80 1 day
7 .. 10 $1,500 .. 2,000 27 days
* 8% of patients require an operation because of indeterminate results.
nephrotomography and ultrasound examination were thought to be free of tumor. Nonetheless, was considered advisable to pursue the tion one step further. Therefore, needle aspiration of the cyst with chemical and cytological examination of the aspirate and double-contrast cystography (using a water-soluble contrast agent) was carried out whenever possible. The technique presently employed utilizes an ultrasonically approach. 6 This examination was performed in 45 per cent of the patients. If the nephrotomograrn did not demonstrate all features of a renal cyst but seemed to be more in keeping with cyst rather than tumor, as was usually the case, cyst puncture was the next procedure used. However, if the nephrotomogram revealed features suggesting tumor, such as a thick wall, aspiration was not done and, instead, arteriography became the procedure of choice. This occurred only twice in the series. Renal masses producing complex patterns ultrasound were also studied next by nephrotornography. Since complex patterns may be by necrotic or hemorrhagic tumors, as well as such benign lesions as renal abscesses, multilocular cysts, polycystic disease and others, 2 it was not surprising to note that a heterogeneous array of nephrotomograms was displayed by patients in this group. Here, again, patients whose tomograms suggested tumor rather than cyst were next scheduled for arteriography rather than cyst puncture, while those with cyst-like characteristics 'Were referred for needle puncture. In the presence of clinical findings suggesting renal abscess or if polycystic disease was thought to be the most likely diagnosis needle puncture was avoided. ' Goldberg, B. B. and Pollack, H. M.: Ultrasonically guided renal cyst aspiration. J. Urol., 109: 5, 1973.
328
POLLACK, GOLDBERG AND BOGASH FLOW DIAGRAM OF PROCEDURES El.'PLOYED IN EVALUATING RENAL MASSES
RENAL l.'ASS
Sol id Pattern
ArteriCX]raphy
Typical Cyst
Atypical Cyst
Probable Cyst
Probable
Non-Cyst
Cyst Aspiration
Arteriography
(arteriography•)
( aspiration•)
• occaslonal!y
Lang has reviewed the findings on double-contrast renal cystography and histochemical analysis of the as pirate.' Our findings are in agreement with his, namely that a cyst is benign if its inner wall is smooth as visualized on multiple projections, including decubitus views. The absence of tumor cells and lack of fat in the cyst fluid also support the diagnosis of renal cyst. However, if any of these parameters is not entirely typical for cyst or if any of them, such as irregularity of the cyst lumen, suggests tumor, arteriography should be done in an attempt to demonstrate vascular evidence of the existence of a tumor. In most cases the aforementioned sequence of studies, without arteriography, is sufficient to establish the diagnosis of renal cyst beyond reasonable doubt and the diagnostic study is concluded following cyst puncture. The question of a possible operation may then be approached not on the basis of whether the mass in question is a cyst or tumor but on the basis of whether the mass, now known to be a cyst, is causing surgically remediable complications. In our series 5 patients were operated upon because of pain, infection or obstruction. There is a small group of patients whose renal masses, even after painstaking effort, resist specific identification. Factors that may contribute to this situation include small masses, masses within the hilus and lack of patient cooperation. In such cases it has been our policy to recommend surgical exploration, unless radiological evidence leans heavily in favor of cyst and clinical considerations make an operation undesirable. Twelve patients (11 per cent) in the series had indeterminate results and 10 of them underwent an operation.
There have been no significant complications attributable to the use of any of the diagnostic modalities previously outlined. Mild flank pain for a few hours following cyst puncture is not uncommon and 2 patients had a transient fever. No tumor has been punctured in this series. If this were to occur we are not certain that it would be of great concern, since we are not aware of any reports of tumor implanting to the needle tract after renal tumor puncture. Not all suspected renal cysts have been punctured. Some patients have refused the procedure and, in a few cases, the cyst has been considered unsuitable for aspiration, either because of its small size or its location. Aside from these relatively uncommon circumstances, we recognize no other contraindications to renal cyst aspiration. We recommend it in almost all patients with suspected renal cysts. The procedure was attempted in 52 patients and was successful in 50. In 48 cases the results of the roentgenographic studies plus the analysis of the aspirate confirmed the absence of malignancy. In 2 cases the cyst fluid contained old blood but at the operation both of these cysts were proved to be benign. Aspiration failed in 2 cases. Both patients were operated upon and benign disease was confirmed. Although these results tend to reinforce the infrequency of tumor developing in the wall of renal cysts there have been occasional reports of the coexistence of these 2 entities' and we are reluctant to abandon the procedure of cyst aspiration as an additional diagnostic refinement. 7 Khorsand, D.: Carcinoma within solitary renal cysts. J. Urol., 93: 440, 1965.
CHANGING CONCEPTS IN DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS
After aspiration and instillation of a water-soluble contrast medium, a renal cyst usually regains its pre-aspiration size within a few months. Exceptions to this rule are uncommon in our hands, although others have claimed otherwise.' Accordingly, we consider cyst aspiration to be a diagnostic and not a therapeutic modality. The instillation of sclerosing agents such as iophendylate* has been reported to cause permanent cyst shrinkage. 8 We as well as others'· 9 have tried and abandoned this technique, having found it to be ineffective. In addition, the frequent retroperitoneal leakage of cyst contents following needle puncture results in a significant incidence of fever and pain when iophendylate is used. Although selective renal arteriography is a highly accurate method of differentiating renal cysts from tumors, it is unsuitable as a screening procedure because of its expense, its small but significant morbidity' 0 and the inconvenience of performing it on outpatients. Sonography, tomography and cyst puncture, on the other hand, are * Pantopaque, E. M. Parker Co. 8 Vest by, G. W.: Percutaneous needle-puncture of renal cysts. New method in therapeutic management. Invest. Radio!., 2: 449, 1967. 9 Stevenson, J. J. and Sherwood, T.: Conservative management ofrenal masses. Brit. J. Urol., 43: 646, 1971. 10 Reiss, M. D., Bookstein, J. J. and Bleifer, K. H.: Radiologic aspects of renovascular hypertension. Part 4. Arteriographic complications. J.A.M.A., 221: 374, 1972.
329
easily done on an outpatient basis and, in instances, we have performed them all on a patient in a single afternoon. Thus, in our hands, arteriography has not been used primary diagnostic study in suspected renal. We consider it indicated in the study of those renal masses having a high likelihood of being turners, that is those masses displaying solid or patterns on nephrosonography or those which calcified. SUMMARY
Renal cysts in 109 patients were studied wii:b systematized diagnostic ul trasound, nephrotomography, cyst puncture and, infrequently, arteriography. The diagnostic accuracy was directly proportional to the of the investigation. When complete study was possible a definitive diagnosis was made in 92 per cent of the patients with accuracy. In 8 per cent of the patients an was thought advisable since diagnostic criteria were not absolute. There were no known cases renal tumor misdiagnosed as renal cyst. Renat cysts can be detected more as accurately by combined ultrasonic and graphic means as by routine An operation for renal cysts for the treatment of complications the cysts and for those cases in which the results of radiographic investigation are indeterminate.
THE JOURNAL OF UROLOGY
Copyright © 1974 by The Williams & Wilkins Co.
Printed in U.S.A.
CHANGING CONCEPTS IN THE DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS HOWARD M. POLLACK, BARRY B. GOLDBERG AND MORTON BOGASH From the Departments of Radiology and Urology, Episcopal Hospital and Temple University Health Sciences Center, Philadelphia, Pennsylvania
Renal cysts occur frequently, especially in elderly subjects. Often asymptomatic, they are far more common than tumors and probably outnumber all other renal masses combined. 1 Cysts are generally indistinguishable from tumors on excretory urography (IVP). Therefore, a battery of studies is used to differentiate the two, including nephrosonography (ultrasound examination), nephrotomography, arteriography and needle puncture. Although the accuracy claimed for such non-surgical methods of investigation has been reported to approach 100 per cent, 2 there are some who still advocate routine surgical exploration of all masses. 3 These investigators believe that only in this way will all tumors be discovered. In view of the prevalence of renal cysts, the philosophy of operating on every renal mass represents a waste of medical resources if the same information may be obtained by non-surgical means. When added to the not-inconsiderable morbidity associated with renal exploration, especially in the elderly, 4 the matter takes on more serious overtones. Therefore, it seems appropriate to review the entire question of the diagnosis of renal cysts.
criterion were applied some tumors might have been misinterpreted as cysts. Nevertheless, we thought that the percentage error within this group would be small and negligible in the entire series. RESULTS
Analysis was made of 109 patients with renal cysts. The number and type of diagnostic examinations performed are listed in table 1. The patients are grouped according to steps, each step representing a succeeding stage of the diagnostic study. After the initial studies of urography and ultrasound only (step 1) the correct diagnosis could be predicted in 89 per cent of the cases with 92 per cent accuracy. The addition of nephrotomography (step 2) allowed the diagnosis to be made in 92 per cent of the patients with 97 per cent accuracy. The addition of cyst puncture and contrast instillation (step 3) made it possible to predict the correct diagnosis in 100 per cent of the cases in which a diagnosis was rendered. The drop-outs between steps 2 and 3 (from 102 to 52 cases) represent those patients in whom cyst puncture was omitted because of patient refusal, size and location of the cyst or the existence of an obvious indication for an operation, precluding the need for further study. The diagnosis in these cases is based on criterion 1 or 3. Of the last 40 renal cysts seen, 33 have been successfully aspirated (82 per cent). All initially incorrect impressions were rectified by the end of step 3. However, in 11 per cent of the group the diagnosis was indeterminate. An operation was recommended in all 12 of these patients and carried out in 10 of them. Renal cysts were present in all. It is noteworthy that during the years encompassed by this study 30 patients with renal tumors were seen. None of these was falsely diagnosed as having a renal cyst.
MATERIAL
The case histories were reviewed of all adults in whom a roentgenographic diagnosis of renal cyst was made between 1968 and 1972. Diagnosis was assumed to be correct if one or more criteria were met: 1) surgical or autopsy proof; 2) radiographic findings typical of cyst, including aspiration and double-contrast studies and 3) other radiographic findings typical of cyst but without cyst aspiration and no change in the size of the mass for 3 or more years. The last criterion only suggests that a neoplasm is not present. Undoubtedly, if only this Accepted for publication July 13, 1973. Read at annual meeting of American Urological Association, New York, New York, May 13-17, 1973. 1 Lalli, A. F.: The direct fluoroscopically guided approach to renal, thoracic and skeletal lesions. In: Current Problems in Radiology. Chicago: Year Book Medical Publishers, Inc., vol. 2, No. 3, 1972. Goldberg, B. B. and Pollack, H. M.: Differentiation of renal masses using A-mode ultrasound. J. Urol., 105:
DISCUSSION
2
765, 1971.
'Leitner, W. A., Anderson, E. E., Weber, C. H., Grimes, J. H. and Johnsrude, I. S.: Limitations of arteriography in renal mass evaluation. Arch. Intern. Med., 130: 868, 1972. 'Kropp, K. A., Grayhack, J. T., Wendel, R. M. and Dahl, D.S.: Morbidity and mortality of renal exploration for cyst. Surg., Gynec. & Obst., 125: 803, 1967. 326
For the last several years our policy in regard to management of renal masses has been, in general, that all pathological renal masses which are not cysts require an operation while, conversely, all those which are cysts do not require operation with the following exceptions: 1) a cyst producing distressing symptoms, usually by virtue of pressure or infection; 2) a cyst producing significant obstruction or otherwise interfering with renal function and 3) all masses thought to be cysts but cannot be conclusively proved radiographically. Clearly, considerable dependence is placed upon
:-l2'7
CHANGING CONCEPTS IN DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS
TABLE
1. Types and accuracy of diagnostic studies in renal cysts Definitive Diagnosis Rendered No.(%)
Rendered Correctly (cyst) No.(%)
Diagnosis Indefinite No. (C:{1)
91 (92)
12 ( 11)
52
97 (89) 94 (92) 48 (92)
91 (97) 48 (100)
8 (8) 4 (8)
13
8 (60)
7 (88)
5 (40)
No. Cases
Step 1 Step 2 Step 3 Step 4
Urography and ultrasound Urography, ultrasound and nephrotomography Urography, ultrasound, nephrotomography and needle puncture Step 2 in conjunction with arteriography
the results of radiographic and sonographic investigation of renal masses, since the outcome of such investigations largely determines whether the patient will be subjected to an operation. Our results indicate that an accurate non-surgical diagnosis of renal cyst is possible in almost all cases, with considerable savings in cost, convenience and safety to the patient (table 2). However, such salutory results require strict adherence to a tightly structured diagnostic protocol (see figure). After a mass was demonstrated by IVP the next study used was nephrosonography. Sonographic patterns in renal masses may be divided into 3 types: 1) the cyst pattern, 2) the solid pattern and 3) the complex pattern. 2 Patients demonstrating a solid pattern were treated as tumor suspects and were studied by arteriography. They will not be discussed further here. Patients with cystic patterns were presumed to have renal cysts, since the likelihood of such an association is approximately 90 per cent. 2 However, this degree of accuracy was considered too low to be clinically acceptable and, in an attempt to improve it further, this group of patients was studied by nephrotomography. This modality, too, is reputed to be approximately 90 per cent accurate in differentiating cysts from tumors, although such precision requires meticulous attention to details of radiographic technique and optimally functioning equipment. In practice, this is difficult to attain consistently, with the result that nephrotomography frequently does not reach its full potential.' Nonetheless, when the classical tomographic findings of renal cyst are clearly demonstrable, the diagnosis may be accepted with the level of confidence cited. These findings include a smooth, pencil-line thin wall visible throughout the protruding portion of the cyst, uniform lucency throughout the cyst and a smooth, sharply contrasted interface at the junction of the cyst and the adjacent renal parenchyma. The presence of a beak or spur at the borders of the cyst-parenchyma junction is not, in our experience, infallible evidence of the presence of a cyst. Patients with typical criteria for renal cysts on 5 Lang, E. K., Johnson, B., Chance, H. L., Enright, J. R., Fontenot, R., Trichel, B. E., Wood, M., Brown, R. and St. Martin, E. C.: Assessment of avascular renal mass lesions: the use of nephrotomography, arteriography, cyst puncture, double contrast study and histochemical and histopathologic examination of the aspirate. Southern Med. J., 65: 1, 1972.
109 102
TABLE
2. Comparison of radiologic versus surgical diagnosis of renal cysts
Diagnostic accuracy Major morbidity Mortality Socioeconomic: Hospital days (av.) Hospital costs (av.) Lost wages (av.)
Radiologic
Surgical
100%*
Approx. 100?0 ;rn?o 4 1.5r;,;1 4
0% 0%
0 .. 1 $1:J0 .. ]80 1 day
7 .. 10 $1,500 .. 2,000 27 days
* 8% of patients require an operation because of indeterminate results.
nephrotomography and ultrasound examination were thought to be free of tumor. Nonetheless, was considered advisable to pursue the tion one step further. Therefore, needle aspiration of the cyst with chemical and cytological examination of the aspirate and double-contrast cystography (using a water-soluble contrast agent) was carried out whenever possible. The technique presently employed utilizes an ultrasonically approach. 6 This examination was performed in 45 per cent of the patients. If the nephrotomograrn did not demonstrate all features of a renal cyst but seemed to be more in keeping with cyst rather than tumor, as was usually the case, cyst puncture was the next procedure used. However, if the nephrotomogram revealed features suggesting tumor, such as a thick wall, aspiration was not done and, instead, arteriography became the procedure of choice. This occurred only twice in the series. Renal masses producing complex patterns ultrasound were also studied next by nephrotornography. Since complex patterns may be by necrotic or hemorrhagic tumors, as well as such benign lesions as renal abscesses, multilocular cysts, polycystic disease and others, 2 it was not surprising to note that a heterogeneous array of nephrotomograms was displayed by patients in this group. Here, again, patients whose tomograms suggested tumor rather than cyst were next scheduled for arteriography rather than cyst puncture, while those with cyst-like characteristics 'Were referred for needle puncture. In the presence of clinical findings suggesting renal abscess or if polycystic disease was thought to be the most likely diagnosis needle puncture was avoided. ' Goldberg, B. B. and Pollack, H. M.: Ultrasonically guided renal cyst aspiration. J. Urol., 109: 5, 1973.
328
POLLACK, GOLDBERG AND BOGASH FLOW DIAGRAM OF PROCEDURES El.'PLOYED IN EVALUATING RENAL MASSES
RENAL l.'ASS
Sol id Pattern
ArteriCX]raphy
Typical Cyst
Atypical Cyst
Probable Cyst
Probable
Non-Cyst
Cyst Aspiration
Arteriography
(arteriography•)
( aspiration•)
• occaslonal!y
Lang has reviewed the findings on double-contrast renal cystography and histochemical analysis of the as pirate.' Our findings are in agreement with his, namely that a cyst is benign if its inner wall is smooth as visualized on multiple projections, including decubitus views. The absence of tumor cells and lack of fat in the cyst fluid also support the diagnosis of renal cyst. However, if any of these parameters is not entirely typical for cyst or if any of them, such as irregularity of the cyst lumen, suggests tumor, arteriography should be done in an attempt to demonstrate vascular evidence of the existence of a tumor. In most cases the aforementioned sequence of studies, without arteriography, is sufficient to establish the diagnosis of renal cyst beyond reasonable doubt and the diagnostic study is concluded following cyst puncture. The question of a possible operation may then be approached not on the basis of whether the mass in question is a cyst or tumor but on the basis of whether the mass, now known to be a cyst, is causing surgically remediable complications. In our series 5 patients were operated upon because of pain, infection or obstruction. There is a small group of patients whose renal masses, even after painstaking effort, resist specific identification. Factors that may contribute to this situation include small masses, masses within the hilus and lack of patient cooperation. In such cases it has been our policy to recommend surgical exploration, unless radiological evidence leans heavily in favor of cyst and clinical considerations make an operation undesirable. Twelve patients (11 per cent) in the series had indeterminate results and 10 of them underwent an operation.
There have been no significant complications attributable to the use of any of the diagnostic modalities previously outlined. Mild flank pain for a few hours following cyst puncture is not uncommon and 2 patients had a transient fever. No tumor has been punctured in this series. If this were to occur we are not certain that it would be of great concern, since we are not aware of any reports of tumor implanting to the needle tract after renal tumor puncture. Not all suspected renal cysts have been punctured. Some patients have refused the procedure and, in a few cases, the cyst has been considered unsuitable for aspiration, either because of its small size or its location. Aside from these relatively uncommon circumstances, we recognize no other contraindications to renal cyst aspiration. We recommend it in almost all patients with suspected renal cysts. The procedure was attempted in 52 patients and was successful in 50. In 48 cases the results of the roentgenographic studies plus the analysis of the aspirate confirmed the absence of malignancy. In 2 cases the cyst fluid contained old blood but at the operation both of these cysts were proved to be benign. Aspiration failed in 2 cases. Both patients were operated upon and benign disease was confirmed. Although these results tend to reinforce the infrequency of tumor developing in the wall of renal cysts there have been occasional reports of the coexistence of these 2 entities' and we are reluctant to abandon the procedure of cyst aspiration as an additional diagnostic refinement. 7 Khorsand, D.: Carcinoma within solitary renal cysts. J. Urol., 93: 440, 1965.
CHANGING CONCEPTS IN DIAGNOSIS AND MANAGEMENT OF RENAL CYSTS
After aspiration and instillation of a water-soluble contrast medium, a renal cyst usually regains its pre-aspiration size within a few months. Exceptions to this rule are uncommon in our hands, although others have claimed otherwise.' Accordingly, we consider cyst aspiration to be a diagnostic and not a therapeutic modality. The instillation of sclerosing agents such as iophendylate* has been reported to cause permanent cyst shrinkage. 8 We as well as others'· 9 have tried and abandoned this technique, having found it to be ineffective. In addition, the frequent retroperitoneal leakage of cyst contents following needle puncture results in a significant incidence of fever and pain when iophendylate is used. Although selective renal arteriography is a highly accurate method of differentiating renal cysts from tumors, it is unsuitable as a screening procedure because of its expense, its small but significant morbidity' 0 and the inconvenience of performing it on outpatients. Sonography, tomography and cyst puncture, on the other hand, are * Pantopaque, E. M. Parker Co. 8 Vest by, G. W.: Percutaneous needle-puncture of renal cysts. New method in therapeutic management. Invest. Radio!., 2: 449, 1967. 9 Stevenson, J. J. and Sherwood, T.: Conservative management ofrenal masses. Brit. J. Urol., 43: 646, 1971. 10 Reiss, M. D., Bookstein, J. J. and Bleifer, K. H.: Radiologic aspects of renovascular hypertension. Part 4. Arteriographic complications. J.A.M.A., 221: 374, 1972.
329
easily done on an outpatient basis and, in instances, we have performed them all on a patient in a single afternoon. Thus, in our hands, arteriography has not been used primary diagnostic study in suspected renal. We consider it indicated in the study of those renal masses having a high likelihood of being turners, that is those masses displaying solid or patterns on nephrosonography or those which calcified. SUMMARY
Renal cysts in 109 patients were studied wii:b systematized diagnostic ul trasound, nephrotomography, cyst puncture and, infrequently, arteriography. The diagnostic accuracy was directly proportional to the of the investigation. When complete study was possible a definitive diagnosis was made in 92 per cent of the patients with accuracy. In 8 per cent of the patients an was thought advisable since diagnostic criteria were not absolute. There were no known cases renal tumor misdiagnosed as renal cyst. Renat cysts can be detected more as accurately by combined ultrasonic and graphic means as by routine An operation for renal cysts for the treatment of complications the cysts and for those cases in which the results of radiographic investigation are indeterminate.