Opinion
Opinion
Colonic Polyp Detection: Role of Roentgenography and Colonoscopy John R. Amberg, M.D., 1 Robert N. Berk, M.D., 1 H. Joachim Burhenne, M.D., 2 Arthur R. Clemett, M.D.,3 Wylie J. Dodds, M.D.,4 Gerald W. Frledland,M.D.,5 Henry I. Goldberg,M.D.,a Harvey M. Goldstein, M.D., 7 Igor Laufer, M.D., 8 Thomas L. Lawson, M.D.,9 Alexander R. Margulis, M.D.,a Richard H. Marshak, M.D.,10Roscoe E. Miller, M.D.,11 Weiland F. Short, M.D.,12 Edward T. Stewart, M.D.,4 James E. Youker, M.D.,4 F. Frank Zboralske, M.D.13 In order to determine the relative yields of colonoscopic and radiologic examinations of the colon, the following guidelines are suggested: (a) prospective data collection; (b) a standard, effective colon cleansing regimen; (c) colonoscopic and radiologic examiners of comparable expertise; (d) examiners should be unaware of each other's findings; (e) a suitable method for demonstrating false-negative findings and for resolving conflicting findings between the two examinations; and (f) indexing of the study findings as to lesion size, lesion location, quality of colon cleansing, and examiner's level of confidence. The two examinations should be used as complementary diagnostic procedures. INDEX TERMS: Colon, neoplasms. (Colon, polypi, • Colonoscopy • Opinions
7[5].311). Colon, radiography
Radiology 125:255-257, October 1977
suggest that the roentgen method compares favorably with colonscopy, especially for lesions a centimeter or larger in size (6-9). Thus, an important question remains to be answered: What are the relative yields of the respective examinations for detecting polypoid lesions in the large bowel? An optimal study comparing the yield of the colonoscopic and roentgen examinations for detecting colonic polypoid lesions should include the following features in its experimental design: (a) prospective data collection; (b) a standard, effective colon cleansing regimen for both examinations; (c) colonoscopic and radiologic examiners of comparable expertise; (d) examiners should be unaware of the findings of the other examiners; (e) a suitable method for demonstrating false-negative findings and for resolving conflicting findings between the two examinations; and (f) indexing of the study findings as to lesion size, lesion location, quality of colon cleansing, and examiner's level
Presently, about 100,000 colorectal carcinomas are diagnosedin the United States each year and nearly 50,000 patients die annually from this malignancy (1). Colorectal carcinomas account for 12 to 15 % of cancer deaths occurring in this country. Estimates of the American Cancer Society suggest, however, that earlier detection of colorectal carcinoma might reduce the death rate by half. Because some colon cancers probably originate from benign adenomatouspolyps (2, 3), a legitimate requirement for an acceptable diagnostic examination of the colonic lumen is accurate identification of polypoid lesions which might harbor malignancy. Since development of the modern fiberoptic colonoscope, an increasing number of patients with suspected or known polypoid colonic lesions are being evaluated by colonoscopy. Some reports suggest that colonoscopy is a more accurate method than roentgen examination for detecting polypoid lesions (4, 5) whereas other reports Department of Department of 3 Department of 4 Department of 5 Department of 6 Department of 7 Department of 8 Department of 9 Department of 10 Department of 11 Department of 12 Department of 13 Department of 1
2
Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology,
University of California, San Diego, Calif. Children's Hospital, San Francisco, Calif. St. Vincent's Hospital, New York, N. Y. The Medical College of Wisconsin, Milwaukee, Wis. The Bowman-Gray School of Medicine, Winston-Salem, N. C. University of California, San Francisco, Calif. M.D. Anderson Hospital, Houston, Texas. Hospital of the University of Pennsylvania, Philadelphia, Pa. The George Washington University Medical Center, Washington, D. C. Mount Sinai School of Medicine, New York, N. Y. Indiana University Medical Center, Indianapolis, Ind. Memorial Hospital, Albany, N. Y. Stanford University, Stanford, Calif.
255
shan
256
OPINION
of confidence. Interestingly, many of these same items also apply to the debate over the value of double contrast versus single contrast roentgen examination for detecting colonic polyps. This topic has been recently considered elsewhere (10, 11). Although the pneumocolon and barium enema examinations are not discussed separately in this paper, it seems clear that these two roentqen examinations need to be individually compared with colonoscopy as well as with one another. Published studies comparing colonoscopy and roentgen examination of the colon lack some or all of the study design features suggested above. The existing reports describe nonblinded, retrospective studies which do not exclude the opportunity for inadvertent observer bias. Usually, no assurance is given that colon cleansing is comparable for the respective examinations. Examiner expertise has often been dissimilar, usually favoring colonoscopy. The colonoscopist usually knew the findings of the roentgen examinations, whereas the radiologist rarely enjoyed a comparable advantage. Lastly, the colonoscopy findings have generally been used to decide whether or not a lesion was present. Although this method can demonstrate lesions missed by xray, it provides no means for determining false-negative findings at colonoscopy. When comparing the diagnostic yield of the colonoscopic and roentgen examinations, investigators should consider several important issues which influence the interpretation of study results. Firstly, the actual number of polypoid lesions present is never really known because false-negative findings may occur for colonoscopy as well as tor the roentgen examination. Generally, surgical specimens are not available to verify the real number of lesions present. At best, therefore, the colonoscopic or roentgen examinations can only approximate the true number of polypoid lesions. Secondly, the results of any comparative study will be significantly affected by the relative level of examiner expertise. For example, expert colonoscopy versus poor radiology would weigh the study findings toward colonoscopy, whereas the reverse circumstance would favor radiology. Interestingly, a study comparing poor colonoscopy versus poor radiology might show a similar yield for both examinations, but the real number of polypoid lesions would be markedly underassessed by both methods. The results of any comparative study are also determined by the method used to resolve conflicting findings between the two examinations. If the findings from a single colonoscopic examination are used to score the presence or absence of a polypoid lesion, this method clearly favors colonoscopy because no means is provided to detect false-negative colonoscopic findings. Additional information from a second colonoscopic or roentgen examination, or surgery is needed to resolve disparate findings between the two examinations. Although colonoscopy rarely yields false-positive findings suggesting a polypoid lesion, false-negative findings are not unusual (7, 9, 12). For example, the finding of a colonic filling defect of
October 1977
identical size and location on two roentgen examinations will nearly always prove to be a real positive finding, irrespective of a negative finding on initial colonoscopy. Lastly, the relative yield of polypoid lesions detected by the colonoscopic and roentgen examinations is influenced by the lesion size which is selected as the basis for comparing the two examinations. For instance, the roentgen examination may be comparable to colonoscopy for detecting polypoid lesions 2:: 1.0 cm in diameter, or perhaps even for lesions 2:: 5 mm in diameter. When small excrescences a few millimeters in size are included in the comparison, however, the yield of colonoscopy is likely to exceed that of the roentgen examination. Consequently, lesion size should be determined and specified because the comparative yield of the two examinations will be significantly influenced by the yardstick chosen for comparison. In addition to consideration of lesion size, an analysis of detection rate might also include evaluation of the effects of lesion location, quality of colon cleansing, and confidence level of the examiner. Once the yield of colonoscopy and roentgen examination for diagnosing polypoid lesions is determined, a second question arises: What significance do the findings from the respective examinations have with regard to satisfactory patient care? Exactly what type and size of polypoid lesions do we wish or need to find? The answers to these questions are clearly influenced by the necessity of accurately detecting early colon carcinomas which are in a curable stage. Current evidence suggests that some colon carcinomas do not develop de novo, but seem to arise within benign adenomatous polyps (2,3). The likelihood of malignancy is related to lesion type and size. Polyps with papillary or villous features are more likely to develop carcinoma than are simple adenomas. Even more important, the incidence of carcinoma is directly related to lesion size. Numerous studies indicate that polypoid lesions a centimeter or less in size have about a 1 to 2 per cent incidence of cancer (2, 13). For polypoid lesions less than 5 mm in size, greater than 90 % are hyperplastic excrescences which are not associated with carcinoma (3). For adenomas less than 5 mm in size the occurrence of focal carcinoma is rare. Thus, as a conservative estimate, the likelihood of carcinoma in a colonic polyp smaller than 5 mm in diameter is less than 1 in 1,000 (3). We believe these facts should influence the selection of realistic goals for the detection and management of polypoid colonic lesions (14). Based on the preceding discussion, we submit several suggestions for consideration. Colonoscopy is not an infallible method for detecting all polypoid lesions of the colon (7, 9, 12). A significant number of polypoid lesions located behind haustral folds or on the inner curvature of colonic flexures may escape detection by the colonoscope (12). A lesion reported as "definite" by the radiologist should not be dismissed by a "negative" colonoscopy. Rather, the roentgen examination or roentgen examination plus colonoscopy should be repeated to resolve the issue.
Vol. 125
257
OPINION
Although colonoscopy appears to be more sensitive than a roentgen examination for demonstrating some polypoid lesions, particularly polyps a few millimeters in size, colonoscopy is not suited for evaluating large numbers of patients. Due to its negligible risk, lower cost, shorter procedure time, and capability for examining the entire colon in virtually all patients, the roentgen method will undoubtedly continue to serve as the appropriate primary method for detecting polypoid colonic lesions. At present, not even the roentgen method is used for all patients who need a colon examination. A consensus appears to be emerging that colonoscopy should be reserved for selected patients, for example, those with unexplained intestinal bleeding or at high risk for colon malignancy. We believe, along with others (6, 8) that the colonoscopic and roentgen examinations are complementary rather than competitive. Colonoscopy clearly represents a major advance in the evaluation and treatment of polypoid colonic neoplasms. Although the roentgen methods have improved greatly during the past two decades, colonoscopy serves as an important forcing principle which exposes substandard roentgen examinations, thereby promoting more conscientious application of existing roentgen techniques and stimulating further improvements in the roentgen method. With cooperative feedback, the colonoscopy findings make review of the x-ray films an important learning experience for both the radiologist and colonoscoplst, Improved patient care undoubtedly results from such interchange. Prospective, well-designed investigations, however, are still needed for a more definitive, direct comparison of the diagnostic yield for the colonoscopic and roentgen examinations. Appropriate attention to sound experimental design will lead to better future studies and wider acceptance of significant results. We enthusiastically welcome the results and interpretation of such studies.
Opinion
REFERENCES 1. Seidman H, Silverberg E, Holleb AI: Cancer statistics, 1976, a comparison of white and black populations. CA 26:2-30, Jan-Feb 1976 2. Morson BC: The polyp-cancer sequence in the large bowel. Proc R Soc Mad 67:451-457, Jun 1974 3. Lane N, Fenoglio CM: The adenoma-carcinoma sequence in the stomach and colon. I. Observations on the adenoma as precursor to ordinary large bowel carcinoma. Gastrointest Radiol 1: 111-119,1976 4. Matsunaga F, Tajima T: Endoscopic studies of colon polyps and polyposis. Am J ProctoI25:41-44, Apr 1974 5. Schmitt MG Jr, Wu WC, Geenen JE, et al: Diagnostic colonoscopy. An assessment of the clinical indications. Gastroenterology 69:765-769, Sep 1975 6. Williams CB, Hunt RH, Loose H, et al: Colonoscopy in the management of colon polyps. Br J Surg 61:673-682, Sep 1974 7. Leinicke JA, Dodds WJ, Stewart ET, et al: Comparison of roentgen and colonoscoplc examination for demonstrating polypoid large bowel lesion (abst). Invest Radio110:448, Sep-Oct 1975 8. Wolff WI, Shinya H, Geffen A, et al: Comparison of c610noscopy and the contrast enema in five hundredpatients with colarectal disease. Am J Surg 129:181-186, Feb 1975 9. Laufer I, Smith NCW, Mullens JE: The radiological demonstration of colorectat polyps undetectedby endoscopy. Gastroenterology 70:167-170, Feb 1976 10. Laufer I: The double-contrast enema: myths and misconceptions. Gastrointest RadioI1:19-31, 1976 11. Margulis AR: Is double-contrast examination of the colon the only acceptable radiographic examination? Radiology 119:741-742, Jun 1976 12. Miller RE, Lehman G: The barium enema. Is it obsolete? JAMA 235:2842-2844,28 Jun 1976 13. Welin S, Youker J, Spratt JS, et al; The rates and patterns of growth of 375 tumors of the large intestine and rectum observed serially by double contrast enema study (Malmo technique). Am J Roentgenoi 90:673-687, Oct 1963 14. Marshak RH, Lindner AE, Maklansky 0: Adenomatous polyps of the colon. A rational approach. JAMA 235:2856-2858, 1976 Wylie J. Dodds, M.D. Department of Radiology Milwaukee County Medical Complex 8700 West Wisconsin Avenue Milwaukee, Wis. 53226
LETTER TO THE EDITOR
Caudad A..-gle View of the Kidneys in Excretory Urography Editor, In the January 1977 issue of Radiology, Imray et al. describe a caudad angle view of the kidneys in excretory urography which they use in selected patients to compensate for the normal foreshortening of the kidney seen on anteroposterior roentgenograms. The approximately 150 inclination of the longitudinalaxis of the kidneys to the coronal plane occurs primarily because of the normal lordotic curve of the lumbar spine. This radiologic foreshortening of the kidneys can be minimized by simply flexing the patient's hips, thereby straightening the lumbar spine. Radiographs obtained with this positioning will decrease the required amount of caudad angulation on the view described by Imray et el., and may obviate the need for this additional roentgenogram.
The normal supine positioning of the patient may be advantageous during renal laminography; the resulting slight difference in height of the upper and lower poles allows the radiologist to better assess the level of the tomograms relative to the kidneys. This is particularly true in excretory urography during the preliminary scout tomogram to determine the optimal levels for subsequent postinjection laminograms.
FERRIS M. HALL,
M.D.
Beth Israel Hospital Boston, Mass. 02115
Opinion
Colonic Polyp Detection: Role of Roentgenography and Colonoscopy John R. Amberg, M.D., 1 Robert N. Berk, M.D., 1 H. Joachim Burhenne, M.D., 2 Arthur R. Clemett, M.D.,3 Wylie J. Dodds, M.D.,4 Gerald W. Frledland,M.D.,5 Henry I. Goldberg,M.D.,a Harvey M. Goldstein, M.D., 7 Igor Laufer, M.D., 8 Thomas L. Lawson, M.D.,9 Alexander R. Margulis, M.D.,a Richard H. Marshak, M.D.,10Roscoe E. Miller, M.D.,11 Weiland F. Short, M.D.,12 Edward T. Stewart, M.D.,4 James E. Youker, M.D.,4 F. Frank Zboralske, M.D.13 In order to determine the relative yields of colonoscopic and radiologic examinations of the colon, the following guidelines are suggested: (a) prospective data collection; (b) a standard, effective colon cleansing regimen; (c) colonoscopic and radiologic examiners of comparable expertise; (d) examiners should be unaware of each other's findings; (e) a suitable method for demonstrating false-negative findings and for resolving conflicting findings between the two examinations; and (f) indexing of the study findings as to lesion size, lesion location, quality of colon cleansing, and examiner's level of confidence. The two examinations should be used as complementary diagnostic procedures. INDEX TERMS: Colon, neoplasms. (Colon, polypi, • Colonoscopy • Opinions
7[5].311). Colon, radiography
Radiology 125:255-257, October 1977
suggest that the roentgen method compares favorably with colonscopy, especially for lesions a centimeter or larger in size (6-9). Thus, an important question remains to be answered: What are the relative yields of the respective examinations for detecting polypoid lesions in the large bowel? An optimal study comparing the yield of the colonoscopic and roentgen examinations for detecting colonic polypoid lesions should include the following features in its experimental design: (a) prospective data collection; (b) a standard, effective colon cleansing regimen for both examinations; (c) colonoscopic and radiologic examiners of comparable expertise; (d) examiners should be unaware of the findings of the other examiners; (e) a suitable method for demonstrating false-negative findings and for resolving conflicting findings between the two examinations; and (f) indexing of the study findings as to lesion size, lesion location, quality of colon cleansing, and examiner's level
Presently, about 100,000 colorectal carcinomas are diagnosedin the United States each year and nearly 50,000 patients die annually from this malignancy (1). Colorectal carcinomas account for 12 to 15 % of cancer deaths occurring in this country. Estimates of the American Cancer Society suggest, however, that earlier detection of colorectal carcinoma might reduce the death rate by half. Because some colon cancers probably originate from benign adenomatouspolyps (2, 3), a legitimate requirement for an acceptable diagnostic examination of the colonic lumen is accurate identification of polypoid lesions which might harbor malignancy. Since development of the modern fiberoptic colonoscope, an increasing number of patients with suspected or known polypoid colonic lesions are being evaluated by colonoscopy. Some reports suggest that colonoscopy is a more accurate method than roentgen examination for detecting polypoid lesions (4, 5) whereas other reports Department of Department of 3 Department of 4 Department of 5 Department of 6 Department of 7 Department of 8 Department of 9 Department of 10 Department of 11 Department of 12 Department of 13 Department of 1
2
Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology, Radiology,
University of California, San Diego, Calif. Children's Hospital, San Francisco, Calif. St. Vincent's Hospital, New York, N. Y. The Medical College of Wisconsin, Milwaukee, Wis. The Bowman-Gray School of Medicine, Winston-Salem, N. C. University of California, San Francisco, Calif. M.D. Anderson Hospital, Houston, Texas. Hospital of the University of Pennsylvania, Philadelphia, Pa. The George Washington University Medical Center, Washington, D. C. Mount Sinai School of Medicine, New York, N. Y. Indiana University Medical Center, Indianapolis, Ind. Memorial Hospital, Albany, N. Y. Stanford University, Stanford, Calif.
255
shan
256
OPINION
of confidence. Interestingly, many of these same items also apply to the debate over the value of double contrast versus single contrast roentgen examination for detecting colonic polyps. This topic has been recently considered elsewhere (10, 11). Although the pneumocolon and barium enema examinations are not discussed separately in this paper, it seems clear that these two roentqen examinations need to be individually compared with colonoscopy as well as with one another. Published studies comparing colonoscopy and roentgen examination of the colon lack some or all of the study design features suggested above. The existing reports describe nonblinded, retrospective studies which do not exclude the opportunity for inadvertent observer bias. Usually, no assurance is given that colon cleansing is comparable for the respective examinations. Examiner expertise has often been dissimilar, usually favoring colonoscopy. The colonoscopist usually knew the findings of the roentgen examinations, whereas the radiologist rarely enjoyed a comparable advantage. Lastly, the colonoscopy findings have generally been used to decide whether or not a lesion was present. Although this method can demonstrate lesions missed by xray, it provides no means for determining false-negative findings at colonoscopy. When comparing the diagnostic yield of the colonoscopic and roentgen examinations, investigators should consider several important issues which influence the interpretation of study results. Firstly, the actual number of polypoid lesions present is never really known because false-negative findings may occur for colonoscopy as well as tor the roentgen examination. Generally, surgical specimens are not available to verify the real number of lesions present. At best, therefore, the colonoscopic or roentgen examinations can only approximate the true number of polypoid lesions. Secondly, the results of any comparative study will be significantly affected by the relative level of examiner expertise. For example, expert colonoscopy versus poor radiology would weigh the study findings toward colonoscopy, whereas the reverse circumstance would favor radiology. Interestingly, a study comparing poor colonoscopy versus poor radiology might show a similar yield for both examinations, but the real number of polypoid lesions would be markedly underassessed by both methods. The results of any comparative study are also determined by the method used to resolve conflicting findings between the two examinations. If the findings from a single colonoscopic examination are used to score the presence or absence of a polypoid lesion, this method clearly favors colonoscopy because no means is provided to detect false-negative colonoscopic findings. Additional information from a second colonoscopic or roentgen examination, or surgery is needed to resolve disparate findings between the two examinations. Although colonoscopy rarely yields false-positive findings suggesting a polypoid lesion, false-negative findings are not unusual (7, 9, 12). For example, the finding of a colonic filling defect of
October 1977
identical size and location on two roentgen examinations will nearly always prove to be a real positive finding, irrespective of a negative finding on initial colonoscopy. Lastly, the relative yield of polypoid lesions detected by the colonoscopic and roentgen examinations is influenced by the lesion size which is selected as the basis for comparing the two examinations. For instance, the roentgen examination may be comparable to colonoscopy for detecting polypoid lesions 2:: 1.0 cm in diameter, or perhaps even for lesions 2:: 5 mm in diameter. When small excrescences a few millimeters in size are included in the comparison, however, the yield of colonoscopy is likely to exceed that of the roentgen examination. Consequently, lesion size should be determined and specified because the comparative yield of the two examinations will be significantly influenced by the yardstick chosen for comparison. In addition to consideration of lesion size, an analysis of detection rate might also include evaluation of the effects of lesion location, quality of colon cleansing, and confidence level of the examiner. Once the yield of colonoscopy and roentgen examination for diagnosing polypoid lesions is determined, a second question arises: What significance do the findings from the respective examinations have with regard to satisfactory patient care? Exactly what type and size of polypoid lesions do we wish or need to find? The answers to these questions are clearly influenced by the necessity of accurately detecting early colon carcinomas which are in a curable stage. Current evidence suggests that some colon carcinomas do not develop de novo, but seem to arise within benign adenomatous polyps (2,3). The likelihood of malignancy is related to lesion type and size. Polyps with papillary or villous features are more likely to develop carcinoma than are simple adenomas. Even more important, the incidence of carcinoma is directly related to lesion size. Numerous studies indicate that polypoid lesions a centimeter or less in size have about a 1 to 2 per cent incidence of cancer (2, 13). For polypoid lesions less than 5 mm in size, greater than 90 % are hyperplastic excrescences which are not associated with carcinoma (3). For adenomas less than 5 mm in size the occurrence of focal carcinoma is rare. Thus, as a conservative estimate, the likelihood of carcinoma in a colonic polyp smaller than 5 mm in diameter is less than 1 in 1,000 (3). We believe these facts should influence the selection of realistic goals for the detection and management of polypoid colonic lesions (14). Based on the preceding discussion, we submit several suggestions for consideration. Colonoscopy is not an infallible method for detecting all polypoid lesions of the colon (7, 9, 12). A significant number of polypoid lesions located behind haustral folds or on the inner curvature of colonic flexures may escape detection by the colonoscope (12). A lesion reported as "definite" by the radiologist should not be dismissed by a "negative" colonoscopy. Rather, the roentgen examination or roentgen examination plus colonoscopy should be repeated to resolve the issue.
Vol. 125
257
OPINION
Although colonoscopy appears to be more sensitive than a roentgen examination for demonstrating some polypoid lesions, particularly polyps a few millimeters in size, colonoscopy is not suited for evaluating large numbers of patients. Due to its negligible risk, lower cost, shorter procedure time, and capability for examining the entire colon in virtually all patients, the roentgen method will undoubtedly continue to serve as the appropriate primary method for detecting polypoid colonic lesions. At present, not even the roentgen method is used for all patients who need a colon examination. A consensus appears to be emerging that colonoscopy should be reserved for selected patients, for example, those with unexplained intestinal bleeding or at high risk for colon malignancy. We believe, along with others (6, 8) that the colonoscopic and roentgen examinations are complementary rather than competitive. Colonoscopy clearly represents a major advance in the evaluation and treatment of polypoid colonic neoplasms. Although the roentgen methods have improved greatly during the past two decades, colonoscopy serves as an important forcing principle which exposes substandard roentgen examinations, thereby promoting more conscientious application of existing roentgen techniques and stimulating further improvements in the roentgen method. With cooperative feedback, the colonoscopy findings make review of the x-ray films an important learning experience for both the radiologist and colonoscoplst, Improved patient care undoubtedly results from such interchange. Prospective, well-designed investigations, however, are still needed for a more definitive, direct comparison of the diagnostic yield for the colonoscopic and roentgen examinations. Appropriate attention to sound experimental design will lead to better future studies and wider acceptance of significant results. We enthusiastically welcome the results and interpretation of such studies.
Opinion
REFERENCES 1. Seidman H, Silverberg E, Holleb AI: Cancer statistics, 1976, a comparison of white and black populations. CA 26:2-30, Jan-Feb 1976 2. Morson BC: The polyp-cancer sequence in the large bowel. Proc R Soc Mad 67:451-457, Jun 1974 3. Lane N, Fenoglio CM: The adenoma-carcinoma sequence in the stomach and colon. I. Observations on the adenoma as precursor to ordinary large bowel carcinoma. Gastrointest Radiol 1: 111-119,1976 4. Matsunaga F, Tajima T: Endoscopic studies of colon polyps and polyposis. Am J ProctoI25:41-44, Apr 1974 5. Schmitt MG Jr, Wu WC, Geenen JE, et al: Diagnostic colonoscopy. An assessment of the clinical indications. Gastroenterology 69:765-769, Sep 1975 6. Williams CB, Hunt RH, Loose H, et al: Colonoscopy in the management of colon polyps. Br J Surg 61:673-682, Sep 1974 7. Leinicke JA, Dodds WJ, Stewart ET, et al: Comparison of roentgen and colonoscoplc examination for demonstrating polypoid large bowel lesion (abst). Invest Radio110:448, Sep-Oct 1975 8. Wolff WI, Shinya H, Geffen A, et al: Comparison of c610noscopy and the contrast enema in five hundredpatients with colarectal disease. Am J Surg 129:181-186, Feb 1975 9. Laufer I, Smith NCW, Mullens JE: The radiological demonstration of colorectat polyps undetectedby endoscopy. Gastroenterology 70:167-170, Feb 1976 10. Laufer I: The double-contrast enema: myths and misconceptions. Gastrointest RadioI1:19-31, 1976 11. Margulis AR: Is double-contrast examination of the colon the only acceptable radiographic examination? Radiology 119:741-742, Jun 1976 12. Miller RE, Lehman G: The barium enema. Is it obsolete? JAMA 235:2842-2844,28 Jun 1976 13. Welin S, Youker J, Spratt JS, et al; The rates and patterns of growth of 375 tumors of the large intestine and rectum observed serially by double contrast enema study (Malmo technique). Am J Roentgenoi 90:673-687, Oct 1963 14. Marshak RH, Lindner AE, Maklansky 0: Adenomatous polyps of the colon. A rational approach. JAMA 235:2856-2858, 1976 Wylie J. Dodds, M.D. Department of Radiology Milwaukee County Medical Complex 8700 West Wisconsin Avenue Milwaukee, Wis. 53226
LETTER TO THE EDITOR
Caudad A..-gle View of the Kidneys in Excretory Urography Editor, In the January 1977 issue of Radiology, Imray et al. describe a caudad angle view of the kidneys in excretory urography which they use in selected patients to compensate for the normal foreshortening of the kidney seen on anteroposterior roentgenograms. The approximately 150 inclination of the longitudinalaxis of the kidneys to the coronal plane occurs primarily because of the normal lordotic curve of the lumbar spine. This radiologic foreshortening of the kidneys can be minimized by simply flexing the patient's hips, thereby straightening the lumbar spine. Radiographs obtained with this positioning will decrease the required amount of caudad angulation on the view described by Imray et el., and may obviate the need for this additional roentgenogram.
The normal supine positioning of the patient may be advantageous during renal laminography; the resulting slight difference in height of the upper and lower poles allows the radiologist to better assess the level of the tomograms relative to the kidneys. This is particularly true in excretory urography during the preliminary scout tomogram to determine the optimal levels for subsequent postinjection laminograms.
FERRIS M. HALL,
M.D.
Beth Israel Hospital Boston, Mass. 02115
