Ventilation and perfusion lung scans were performed pre. operatively and .... gram became positive or if the leg scan became positive over the popliteal or ...
Care, Am Hosp Assoc, Chicago, 1975 20. Ontario Ministry of Health: Drug Benefit Formulary, Queen's Printer, Toronto, 1978 21. A glossary for primary care. Report of the North American Primary Care Research Group (NAPCRG) committee on standard terminology. J Fain Pract 1977; 5: 633-638 22. SKOLL SL, AUGUST RJ, JOHNSON GE: Drug prescribing
for the elderly in Saskatchewan during 1976. Can Med Assoc J 1979; 121: 1074-1081 23. ROSSER WW: Interpractice drug utilization review: a method of continuing medical education in the 1980s. Can Fain Physician (in press) 24. Idem: Why do we give middle aged women so many tranquilizers? Posigrad Med (in press)
The low specificity of postoperative perfusion lung scan defects IRWIN WALKER, MB, BS, FRACP, FRCP[C]; PAUL AUKLAND, MB, CH B, FRCS; JACK HIRSH, MD, FRACP, FRC P[C]; GEOFFREY COATES, MB, BS, M SC, FRCP[C]; PETER COCKSHOTT, MB, CH B, MD, DMRD, MRCP (EDIN & LOND), FRCP[C]; ROBERT TAYLOR, MD, FRC P[C]; RUSSELL HULL, MB, BS, FRACP, FRCP[C]
Ventilation and perfusion lung scans were performed pre. operatively and postoperatively in 169 patients and classified blindly according to preset criteria. Perfusion lung scan abnormalities were present in 25 (lS0/o) of the preoperative scans and 42 (2Sd/o) of the postoperative scans; 16 (380/o) of the 42 abnormal postoperative scans were identical to the preoperative scans. Perfusion defects indicating a "high probability" of pulmonary embolism (lobar or segmental defects) were present in 5 preoperative scans and 10 post. operative scans; the 10 postoperative scans were classified as showing "definite" (5), "possible" (1) or "no" (4) pulmonary embolism on the basis of the preoperative scan and the ventilation scan; none of the 10 patients had clinical evidence of pulmonary embolism. Venous thrombosis was present in 12 patients, including 4 of the patients whose lung scans showed definite pulmonary embolism. Thus, postoperative perfusion lung scan defects are potentially misleading even when large. Des scintigraphies pulmonaires de ventilation et de per. fusion ont ete effectu6es en pre. et en postop6ratoire chez 169 malades et classifi6s en aveugle selon des crit.res pre-etablis. Des anomalies de Ia scintigraphie de perfusion 6taient presentes dans 25 (150/o) des scintigraphies pr6. operatoires et dans 42 (250/o) des scintigraphies postopera. toires; 16 (380/o) des 42 scintigraphies postoperatoires anormales etaient identicjues aux scintigraphies preoperatoires. Des defauts de perfusion indiquant une "forte probabilit6" d'embolie pulmonaire (d6fauts lobaires ou segmentaires) etaient presents dans 5 scintigraphies preop6ratoires et 10 scintigraphies postoperatoires; les 10 scintigraphies post. op6ratoires ont et6 classiflees comme demontrant une embolie pulmonaire "certaine" (5) ou "possible" (1), ou l'ab. sence d'embolie (4) a partir de Ia scintigraphie preop6ra. loire et de Ia scintigraphie de ventilation; aucun des 10 malades ne pr6sentait de signes cliniques d'embolie pulmonaire. Une thrombose veineuse etait presente chez 12 From the departments of medicine, pathology, surgery and radiology, McMaster University Reprint requests to: Dr. Jack Hirsh, Department of pathology, McMaster University, 1200 Main St. W, Hamilton, Ont. L8N 3Z5
patients, dont 4 des malades dont les scintigrap.iies montraient une embolie pulmonaire certaine. Les anomalies des scintigraphies de perfusion postoperatoires peuvent donc .tre trompeuses m6me Iorsqu'elles sont importantes.
Perfusion lung scanning is commonly performed in patients with suspected pulmonary embolism. The defects seen on the scan are, however, often nonspecific and may be seen in healthy individuals1 as well as asymptomatic patients who have no evidence of pulmonary embolism by pulmonary angiography.' The predictive value of the perfusion lung scan in patients with suspected pulmonary embolism can be increased by classifying the perfusion defects as lobar or segmental ("high-probability") or as subsegmental ("low-probability"), and by comparing the perfusion scan with the ventilation scan. In patients suspected of having a pulmonary embolism pulmonary angiography confirms this diagnosis in about 80% of those with high-probability perfusion defects but in only 15% of those with low-probability defects.3 Ventilation scanning further increases the predictive value of the perfusion scan so that among patients with normal ventilation scans pulmonary embolism is confirmed by angiography in virtually all those with high-probability perfusion defects and in half of those with lowprobability defects.4 The frequency of pulmonary embolism in patients with matching ventilation and perfusion defects and a normal chest roentgenogram is unknown but probably very low. Perfusion lung scan defects have been reported in up to 60% of patients who have just undergone an operation.5" These defects could be caused by pulmonary disorders present preoperatively, nonembolic postoperative pulmonary complications or postoperative pulmonary embolism. The high frequency of nonembolic pulmonary events in the postoperative period increases the likelihood of perfusion defects that mimic pulmonary embolism (high-probability defects), and because most nuclear medicine departments cannot CMA JOURNAL/JANUARY 15, 1981/VOL. 124
153
perform ventilation scanning the cause of these defects remains unknown in many instances. We have investigated the value and limitations of classifying postoperative perfusion lung scan defects as being of high or low probability by performing preoperative and postoperative perfusion lung scans on patients undergoing elective operations. By doing scans preoperatively we were able to identify the patients whose postoperative perfusion defects were clearly caused by preoperative lung disease. We also performed ventilation scanning and so were able to determine the frequency with which ventilation/perfusion mismatching and matching occurred in patients with both new high-probability postoperative perfusion defects and high-probability perfusion defects that had been present preoperatively. Patients and methods
Patients Patients admitted to hospital for major elective surgical procedures were selected for the study provided they gave informed consent and provided perfusion and ventilation lung scanning facilities were available in the department of nuclear medicine. Whenever possible patients clinically judged to be at high risk of pulmonary embolism were selected over patients at low risk. No specific prophylaxis against venous thrombosis was used, but early ambulation was encouraged. Scanning methods Leg scanning with iodine-i 25-labelled fibrinogen and impedance plethysmography were performed as previously described;7'8 the '.I-fibrinogen was injected immediately after the operation. Four-view perfusion lung scanning was performed with a dual-probe rectilinear scanner after the injection of 2 mCi of technetium-99m-labelled macroaggregates of albumin. Immediately afterwards ventilation scanning9 was performed with 2 to 3 mCi of xenon 127; it was performed in the posterior view if the perfusion scan was normal, otherwise it was performed in the view that corresponded to the perfusion abnormality. The data were recorded with a y-camera (Conuclear, Conuclear Ltd., Ottawa) interfaced to a digital computer (model PDP 11/45, Digital Equipment Corporation, Marlborough, Massachusetts) and were analysed during "wash-in" of the "7Xe, after 5 minutes of rebreathing (equilibration) and during washout of the radioisotope. Study design (Fig. 1) Perfusion and ventilation lung scanning and posteriorand lateral-view chest roentgenography were performed within 72 hours before the operation and 7 to 10 days after the operation; in a few cases there was delay because of patient immobility. Scanning was performed daily after the operation over 16 points on each leg. Impedance plethysmography was performed on the second, third and fourth postoperative days and then on alternate days. If the results of either leg scanning or impedance plethysmography became positive, bilateral ascending venography was performed: it was 154 CMA JOURNAL/JANUARY 15, 1981/VOL. 124
performed immediately if the impedance plethysmogram became positive or if the leg scan became positive over the popliteal or femoral region, but it was delayed for up to 5 days if the leg scan was positive in the calf region only, and during this time leg scanning and impedance plethysmography were performed daily. Interpretation of lung scans Criteria were developed before the study for interpreting postoperative lung scans, which were classified as showing definite pulmonary embolism (a new perfusion defect of segmental size or greater and a ventilation/perfusion mismatch), possible pulmonary embolism (a new subsegmental perfusion defect and a ventilation/perfusion mismatch or match, or a new perfusion defect of segmental size or greater and a ventilation/ perfusion match) or no pulmonary embolism (a normal lung scan or an abnormal scan that did not differ from the preoperative scan). The lung scans and chest roentgenograms were interpreted independently and without knowledge of the results of the leg scanning and impedance plethysmography. Results Patients Of the 192 patients selected for the study 23 were excluded because their investigations were not completed. Four of the 23 died before postoperative lung scanning could be performed; all underwent autopsy and in none was a pulmonary embolus found. Complete data were available on the remaining 169 patients. There were 90 men and 79 women. Their mean age was 56 years, and 19 patients were under 40 years of age. The operations performed are listed in Table I; 26 were for malignant disease. Lung scan findings These are summarized in Table II and Fig. 2. Of the 169 postoperative perfusion lung scans 5 (3%) were interpreted as showing definite pulmonary embolism: in 4 there were multiple segmental defects and in 1 there was a single segmental perfusion defect; all 5 patients had a normal ventilation scan and no clinical evidence of pulmonary embolism. In 21 patients (12%) the postoperative lung scan was interpreted as showing DAYS
12345678910
-2-1
S LUNG SCAN CR
U R -
LEG SCAN
IPG
TIME IN DAYS
FIG. 1-Study design. CR = chest roentgenography; IPG = impedance phethysmography.
possible pulmonary embolism: 4 had a new subsegmental perfusion defect and a ventilation/perfusion mismatch, 5 had a new segmental perfusion defect and a ventilation/perfusion match (4 had a matching chest roentgenographic abnormality) and 12 had a new subsegmental defect and a ventilation/perfusion match (3 had a matching chest roentgenographic abnormaJity). None of the 21 patients had been clinically suspected of having pulmonary embolism, and the 7 with abnormal chest roentgenographic findings were considered to have had atelectasis or pneumonia. The remaining 143 postoperative lung scans (85%) were interpreted as showing no pulmonary embolism: 127 were normal; the other 16 were abnormal but did not differ from the preoperative scan. Abnormalities were evident in 25 (15%) of the preoperative perfusion lung scans: there were 20 subsegmental defects and 5 segmental defects. All 25 patients had abnormal ventilation scans. Postoperatively 42 (25%) of the lung scans were abnormal; 16 (38%) of the 42 were associated with an identically abnormal preoperative scan. Of the 16 scans 12 had subsegmental defects and 4 had segmental defects. Postoperative venous thrombosis Of the 169 patients 13 had a positive leg scan and I a positive impedance plethysmogiam, for a total of Table I-Operations performed on the 169 patients Type of operation Biliary Gastric Colonic Aortic Hip Thoracic Miscellaneous
No. of patients 50 22 26 13 16 11 31
Table Il-Correlation of postoperative perfusion lung scan findings with the presence of venous thrombosis and chest roentgenographic abnormalities No. of patients With matching chest With venous roentgenographic abnormality thrombosis
Lung scan Total finding Definite pulmonary 5 4 embolism Possible pulmonary 21 4 embolism* New subsegmental defect with V/P 4 2 mismatch New segmental defect 1 with V/P match 5 New subsegmental defect with V/P match 12 it 4 No pulmonary embolism 143 127 2 Normal lungscan Abnormal but un2 changedlungscan 16 = ventilation/perfusion. tIn this patient venography was not performed.
PREOPERATiVE
Result
No.
No.
0
.
7
0
POSTOPERATIVE vi. SCAN
PERFUSION SCAN
Normal
144
0
Subsegmental
20
4
Segmental
0
EmbolIsm .
1 127 Normal No Pulmonary
3 0
Result Definite Pulmonary
.
Totals
169
12 } 16 Unchanged
Embolism
.o .
Possible Pulmonary Embolism
21
Table Ill-Data for the five patients with pulmonary embolism
Variable Day leg scan became positive Day impedance plethysmogram became positive Venous thrombosis* Iliac Femoral Popliteal Calf Day venography was performed Day lung scanning was performed Age(yr) Sex Operation
1
2
Patient no. 3
4
4
2
4
9
-
-
-
10
0 1 0 R 7
0 0 0 B 7
0 0 0 I 6
0 0 0 B 10
0 0 0 0 10
8 70 F Cholecystectomy
8 57 M Aortofemoral bypass graft
7 56 F Hip replacement
10 30 M Total colectomy
9 50 M Hiatus hernia repair (Belsey)
*0 = absent; I = left-sided; R = right-sided; B = bilateral.
5
We are indebted to Dr. James F. Lind and other members of the department of surgery for their cooperation, to Dr. Edmund S. Garnett, head, department of nuclear medicine, for his assistance and to Mrs. Lorraine Pipher and Mrs. Ruth Shankland for providing excellent technical support. The study was supported by a health research grant (PR143) from the Ontario Ministry of Health and by grants from the Canadian and Ontario heart foundations and the Ontario Thoracic Society.
References 1. TETALMAN MR, HOFFER PB, HECK LL, et al: Perfusion lung scan in normal volunteers. Radiology 106: 593, 1973
2. ROBIN ED: Overdiagnosis and overtreatment of pulmonary embolism: the Emperor may have no clothes. Ann intern Med 87: 775, 1977 3. MosEs DC, SILVER TM, BooKsTEIN JJ: The complementary roles of chest radiography, lung scanning, and selective pulmonary angiography in the diagnosis of pulmonary embolism. Radiology 49: 179, 1974 4. MCNEIL BJ: A diagnostic strategy using ventilation-perfusion studies in patients suspect for pulmonary embolism. J Nuci Med 17: 613, 1976
5. ABERNETHY EA, HARTSUCK JM: Postoperative pulmonary embolism: a prospective study utilizing low dose heparin. Am J Surg 128: 739, 1974 6. JOHANSSON E, ERIcsoN K, ASARD PE: Postoperative leg vein thrombosis and pulmonary embolism after upper abdominal operations. Acta Chir Scand 141: 522, 1975 7. GALLUS AS, HIRsH J, TUTTLE RJ, et al: Small subcutaneous doses of heparin in prevention of venous thrombosis. N Engi J Med 288: 545, 1973 8. HULL R, VAN AKEN WG, HIRSH J, et al: Impedance plethysmography using occlusive cuff technique in diagnosis of venous thrombosis. Circulation 53: 696, 1976 9. COATES G, NAHMIAS C: Xenon-127, a comparison with xenon- 133 for ventilation studies. J Nuci Med 18: 221, 1977 10. NOvELLINE RA, BALTAROWICH OH, ATHANASOULIS CA,
et al: The clinical course of patients with suspected pulmonary embolism and a negative pulmonary arteriogram. Radiology 126: 561, 1978 11. COVEY TH, SHERMAN L, BAUE AE: Low-dose heparin in
postoperative patients - prospective, coded study. Arch Surg 110: 1021, 1975 12. BROWSE NL, CLEMENSON G, CROFT DN: Fibrinogen-
detectable thrombosis in the legs and pulmonary embolism. Br Med 1 1: 603, 1974
Regional program for the study of glomerulonephritis CENTRAL COMMITTEE OF THE TORONTO GLOMERULONEPHRITIS REGISTRY*
The Toronto Glomerulonephritis Registry, a regional program for studying the natural history of the different types of glomerulonephritis and the effects of drug therapy on them, was established 6 years ago in Toronto. Data for all patients with histologic evidence of glomerulonephritis seen at the 16 participating hospitals are collected on standard forms and stored in a computer. Randomized controlled trials of different types of therapy for five types of glomerulonephritis have been started under the coordination of the central registry. In view of the registry's low cost and high potential benefit, greater support for such projects is needed. Other centres should consider establishing similar registries to promote more rapid collection of cases and *Central committee: Drs. D.C. Cattran (chairman), C.J. Cardella, R.C. Charron. M.D. Johnson, C.P. Rance, S. Ritchie and J.M. Roscoe. Other participating nephrologists: Drs. G.S. Arbus, J.W. Balfe, R.A. Bear, W. Berry, W.T.W. Clarke, G.A. de Veber. 1.0. Elkan, S.S.A. Fenton, M.B. Goldstein, P.F. Halloran, M.R. Hockley, S.Y. Karanicolas, A.G. Logan, ME. Manuel, P.S.Y. Ng, D.G. Oreopoulos, A. Rapoport, C.S. Saiphoo, M. Silverman, G.W. Smith, D.S. Thompson, P.R. Uldall, L.M. Wiertz, C.C. Williams and D.R. Wilson. Other participating pathologists: Drs. R. Baumal, A. Katz, A.P. Lang and M.D. Silver. Biostatistician: Dr. P.N. Corey. Registrar: R.E. Guinn. Reprint requests to: Dr. D.C, Cattran, Chairman, Central committee, Toronto Glomerulonephritis Registry, Rm. 3-215, College Wing, Toronto General Hospital, Toronto, Ont. M5G 1L7 158
CMA JOURNAL/JANUARY 15, 1981/VOL. 124
thus allow better evaluation of the development and treatment of this major cause of renal failure. Le Registre Torontois pour Ia Glomerulonephrite (Toronto Glomerulonephritis Registry), un programme regional qui est consacre a l'etude de l'histoire naturelle des differents types de glomerulonephrites et des effets de leur traitement medicamenteux, a ete etabli il y a 6 ans a Toronto. Les donnees pour tous les malades avec des signes histologiques de glomerulonephrite qui sont re.us dans 16 h8pitaux participants sont enregistrees sur des formulaires standards et conservees sur ordinateur. Sous Ia coordination du registre central, des etudes contr6lees et randomisees ont ete mises en route pour cinq types de glomerulonephrites. Compte tenu des faibles frais du registre et de ses importants bienfaits possibles, un meilleur appui pour de tels projets est necessaire. Dautres centres devraient envisager Ia mise sur pied de registres semblables af in de favoriser une collection plus rapide des cas, qui permettra de Ia sorte une meilleure evaluation du developpement et du traitement de cette cause majeure d'insuffisance renale.
In August 1974 The Toronto Glomerulonephritis Registry was initiated. The main aims of the registry were to allow longitudinal observation of the natural history of all major histologic types of glomerulonephritis seen in the surveyed area and to provide a base for properly constructed therapeutic trials. Since we
