Thorax: first published as 10.1136/thx.28.2.198 on 1 March 1973. Downloaded from Thlorax (1973), 28, 198.
Radiographic signs of pulmonary embolism and pulmonary infarction
S. TALBOT, B. S. WORTHINGTON, and E. J. ROEBUCK General Hospital, Nottingham
A comparative analysis of the radiographic features in a group of patients dying with pulmonary embolism and/or pulmonary infarction, and a group without but suspected of having the condi- tions before death, showed that two radiologists could diagnose pulmonary infarction correctly in 70% of cases. The most useful radiographic sign was elevation of the diaphragm often with slight atelectasis and a small unilateral effusion. The plain chest radiograph was of little value in diagnosing pulmonary embolism without infarction.
Many radiographic signs of pulmonary embo- death (mean 1-96 days, SD 12), and six, of whom lism and infarction have been described in three had fibrosed infarcts, within three weeks. Three clinical cases (Fleischner, 1959; Westermark, cases of sudden massive embolism had radiographs taken shortly after symptoms occurred and within 1938). However, pulmonary embolism and infarc- four hours tion are frequently wrongly diagnosed, often being of death. missed and sometimes diagnosed when pulmon- copyright. ary infection or carcinoma are present. Marshall TABLE I (1965) stressed three radiological signs of infarc- PATHOLOGY OF NECROPSY CASES tion, namely, the shadow produced by the lesion, Pathological Diagnosis No. of Necropsies evidence of a pleural effusion, and a raised dia- Control No emboli or infarcts 57 phragm. Less frequent features associated with Thromboembolism Pulmonary emboli only 17 http://thorax.bmj.com/ Pulmonary infarction 3 embolism are increased radiotranslucency, pul- only monary oedema, and prominent main pulmonary Pulmonary embolism 46 arteries. These may, however, occur in other con- and infarction ditions, and it was therefore decided to take a control group of patients to find if any of these Twenty-three per cent of these cases had fractured changes are usually diagnostic of infarction, and femurs, and 6-9% died following abdominal surgery. also to show whether radiologists can diagnose Although it was difficult to identify the time of onset pulmonary embolism and infarction from routine of embolism or infarction this was usually a few days To be certain of the from death (4x8 days, SD 2-9 days). Clinical features on September 29, 2021 by guest. Protected plain radiographs. diagnosis, which in retrospect were typical of pulmonary emboli / only patients in whom necropsy evidence was infarction were recorded for 39 patients. These were available were studied. haemoptysis (10 patients), sudden dyspnoea (21 PATIENTS AND METHODS patients), pleuritic pain (9 patients), angina (3 patients), and syncope (5 patients). Often there was gradual From the hospital necropsy records of 1967 to 1970 deterioration with confusion and coma. Signs of con- inclusive, cases of pulmonary embolism and infarction solidation were noted in 15 patients and signs of a were selected if they had a chest radiograph. From 'pleural effusion' in five patients. Often the radio- the case records the date of the radiograph in relation graphs were performed to elucidate coincidental to death was determined, and radiographs showing infections or cardiac failure. evidence of infarction (>3 cm in diameter) or embolism The pathological examination included examination which was later proved at necropsy were selected. of the major, lobar, and segmental vessels. If thrombus This usually meant that only cases in whom infarction was firmly adherent it was assumed that embolism had been present for 48 hours or cases with necropsy had occurred at least 48 hours before death, and if evidence of fresh infarction, who had had a radio- lightly adherent at least 24 hours before death. Addi- graph performed from 12 to 24 hours before death, tional fresh embolism was not considered. There was were included. Of the 66 cases with emboli/infarction one case with an organized fibrosed pulmonary arterial (Table 1), 57 had radiographs within one week of occlusion, which was probably embolic. 198 Thorax: first published as 10.1136/thx.28.2.198 on 1 March 1973. Downloaded from Radiographic signs of pulmonary embolism and pulmonary infarction 199
At necropsy only 16 cases had unilateral emboli: the correct diagnosis, either by diagnosing infarc- of the 63 cases with emboli, 21 had major pulmonary tion or embolization when they were present or by artery emboli (±other emboli), 20 had lobar emboli not doing so when they were absent. Below this (± segmental emboli), and 22 had segmental emboli the incorrect diagnoses are analysed by a similar only. Of the 49 cases with infarcts, massive lobar method. infarcts were found in 7, infarction (>3 cm) in 35, and multiple small infarcts (<3 cm) were found in 7. At the time of the radiograph, in 31 cases there was right lower lobe infarction and in 23 cases left TABLE III lower lobe infarction: eight were bilateral. There RADIOLOGICAL DIAGNOSIS' CORRELATED WITH PATHOLOGICAL DIAGNOSIS were two cases with right upper lobe infarction alone, and of three left upper lobe infarctions two also had Radiologist A Radiologist B infarction elsewhere. There was one case with an Emboli Infarcts Emboli Infarcts abscess secondary to a right lower lobe infarction. A control series consisted of 57 radiographs from Correct diagnosis 66 92 71 81 Incorrect 57 31 52 42 1969 to 1970 on patients in whom the diagnosis of diagnosis pulmonary embolism or infarction was suspected Correct positive 19 24 27 17 Correct negative 47 68 44 64 at the time of their radiographs, but who did not Incorrect positive 13 6 16 10 have these conditions at necropsy; 24-5% were sur- Incorrect negative 44 25 36 32 gical cases. The causes of death in this control group 'A positive radiological diagnosis was made if there were radiological were usually pneumonia (29 cases), left ventricular features of infarction or emboli. failure (10 cases), myocardial infarction (7 cases), and carcinoma (6 cases). The percentage correct diagnosis of pulmonary The combined series of radiographs were then shown infarction was 74-7% for A and 65-8 % for B. to two radiologists, A and B, without the patient's The percentage correct diagnosis of pulmonary name or the pathological features being known and embolism was 53-6% for A and 57-7% for B. they were asked to comment on the radiological Thus the diagnosis was correct in 70% of features and whether they thought pulmonary infarc- patients with pulmonary infarction and in 55% copyright. tion was present. They also commented on the visibility of patients with pulmonary embolism. of the pulmonary vessels and whether they were normal or compatible with embolism. (If the lobar The probability of these figures being due to vessels were obscured by consolidation, they were con- chance for radiologist A was <0 01 for infarction sidered abnormal.) They commented on any other but not significant for emrbolization, xe being 24-6 features suggestive of embolism, and particularly and 0-75 respectively. For radiologist B, X2=6 54 http://thorax.bmj.com/ cardiomegaly, pleural effusions, pulmonary oedema, (P
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FIG. 1. Radiograph of a patient who subsequently died with pulmonary embolism/infarction: note high right diaphragm and cardiomegaly. http://thorax.bmj.com/ cardiomegaly). Correlation of an elevated dia- bined in the pathological and radiographic phragm and pulmonary infarction was most sig- analysis, as in Table V (for radiologist A, X3= nificant (x2=33 3, P Radiographic signs of pulmonary embolism and pulmonary infarction 201 FIG. 2. Radiograph of a patient who subsequently died with pulmonary copyright. embolism/infarction: note basal lung collapse with a linear atelectasis at the right base. http://thorax.bmj.com/ TABLE VI occur in infarction they do not all appear to be of AGREEMENT AND DISAGREEMENT BETWEEN RADIO- great diagnostic value. LOGISTS AND THEIR CORRELATION WITH PATHOLOGICAL DIAGNOSIS Short (1951) found pleural involvement in 56% of with Agreement among Radiologists patients pulmonary infarction, but pleural effusion was found in only 33 %. In the present Correct Incorrect No. of Cases study 261 % of patients with pulmonary infarcts Emboli 48 34 82 had small unilateral effusions, and 12-3 % of Infarction 76 26 102 patients with pneumonic consolidation. Chang Disagreement among Radiologists (1967) and Chang and Davis (1965) suggested that on September 29, 2021 by guest. Protected Correct Correct No. of Cases (A) (B) dilatation of one or other pulmonary artery was an important sign of pulmonary infarction but Emboli 18 23 41 Infarction 16 5 21 their observations were uncontrolled and few necropsies were reported. Dilatation, which later regresses, in conjunction with other changes is DISCUSSION useful supportive evidence of pulmonary infarc- tion. However, an isolated observation (which is From this retrospective controlled necropsy study, usually all there is) of a left pulmonary artery two radiologists were able to diagnose pulmonary of 17 mm or more in width, or a right pulmonary infarction correctly in 70% of cases. artery of more than 16 mm, with measurements Smith (1938), Short (1951), Macleod and Grant made at the widest point of the arteries (usually (1954), Smith (1953), and Stein et al. (1959) have between the eighth and ninth ribs posteriorly in all described radiological abnormalities in pul- deep inspiration) does not seem of any value in monary infarction but all these series have been the diagnosis of infarction or embolism. In this predominantly of clinical cases without necropsy series, measurements were made when the vessels confirmation. Although these abnormalities may were visible on such radiographs and no difference Thorax: first published as 10.1136/thx.28.2.198 on 1 March 1973. Downloaded from -20-2 S. Talbot, B. S. Worthington, and E. J. Roebuck was observed between the controls and patients dence of this finding in the embolic group, and with pulmonary emboli or infarction. Oblitera- the inequality of such elevation on the two sides tion of pulmonary vessels and areas of radio- was often of diagnostic value even in supine radio- translucency were also inadequate signs of emboli. graphs. However, the radiologists' diagnostic Radiological evidence of embolism without in- accuracy could have been increased by the exclu- farction was stressed by Westermark (1938). He sion of infarcts that were too recent for the found absence of pulmonary vascular shadows, analysis. There is doubt as to the interval between sometimes with enlargement of the hilar shadow the onset of embolism and symptoms and signs after large emboli, and others have also noted of infarction (and sometimes of embolism) occur- this (Teplick, Haskin, and Steinberg, 1964; ring, and although such features had often occur- Arendt and Rosenberg, 1959; Shapiro and Rigler, red they could not be used to date the time of 1948; Torrance, 1963; Woesner et al., 1953). infarction. Thus smaller and earlier infarcts, if Stein et al. (1959) did not observe it and in the included, might have been missed by the radio- present study only one case satisfactorily showed logists. it. In animal experiments it was impossible to The usual criticism of a retrospective necropsy produce an area of radiological oligaemia (Mar- study is that emboli may be missed. Since in all shall et al., 1963). This sign of Westermark has the control patients the diagnosis of pulmonary also been reported in chronic pulmonary artery embolism was under consideration it is unlikely throm-bosis (Hollister and Cull, 1956) but it is that emboli in the segmental vessels or above often found in areas of emphysema. were missed. Smaller emboli are of unknown sig- Laur (1963) thought that visualization of a nificance. In the embolic group all the emboli may defect in a vessel was a direct sign of embolism, not have been documented but it is unlikely that but this was not seen in this study. Hyperaemia such omissions have decreased the accuracy of on the opposite side to an embolism (Fleischner, the radiologists' diagnosis of embolism. 1959) and pulmonary oedema due to an embolism The only other necropsy study of pulmonary (Fieischner, 1959) were not observed in this study. embolism and infarction was that of Hamptoncopyright. Left ventricular failure was often found in both and Castleman (1940) in which necropsy findings groups in the present study but there was no evi- were correlated with chest radiographs performed dence of an association between this and embolism post mortem in the erect position. This may be and infarction. Fleischner (1962) considered areas why they did not detect elevation of the dia- of radiotranslucency or abrupt termination of phragm. An infarct could be of any shape in http://thorax.bmj.com/ blood vessels as important radiographic signs of the PA projection but often appeared like a emsboli but these signs seem rare and not easy cushion. They stressed that in the PA or AP to distinguish from areas of emphysema. Areas of radiographs the shadow may be masked by the pulmonary shadowing or cardiomegaly may ob- heart or diaphragm, and that it was missed in scure the pulmonary vessels and only serial films 25% of cases. It was easily confused with areas of will elucidate such changes. pulmonary oedema, infection, and atelectasis. The failure of the radiologists to diagnose pul- Linear atelectasis are signs of old infarction monary embolism was not due to the method (Fleischner, 1962). Simon (1970) felt that of -such on September 29, 2021 by guest. Protected analysis. They rarely noted radiological features lines could be due to secondary pulmonary of emboli. Therefore any other method of analy- venous thrombosis and then the line was directed sis would have resulted in a larger number of to the hilum. In retrospect only one case could false negative diagnoses and would not have im- be considered to have this sign and only one proved the diagnostic accuracy. The standard of other had a small linear shadow which was due the radiographs in the control and embolic groups to an old infarct. Good lateral radiographs would was similar, in view of the comparability of their probably have helped in detecting such lesions clinical condition, and an error in diagnosis of but are usually unobtainable. pulmonary embolism/infarction was as often Although by no means diagnostic (Laur, 1963; false positive as false negative in both control Barritt and Jordan, 1961), the most useful sign and embolic groups. of -pulmonary infarction in PA radiographs in There were equal proportions of surgical cases the present study was an elevated diaphragm. in both control and embolic groups although However, this sign was present in less than 50% there were few traumatic cases in the control of cases and its absence should not make the group. Therefore elevation of the diaphragmn clinician exclude pulmonary embolism and after laparotomy could not explain the high inci- infarction. Thorax: first published as 10.1136/thx.28.2.198 on 1 March 1973. Downloaded from Radiographic signs of pulmonary embolism and pulmonary infarction 203 We are grateful to the Departments of Radiography Marshall, R. J. (1965). Pulmonary Embolism. Mechanism and and Photography for their assistance, and also to the Management. Thomas, Springfield, Illinois. Department of Pathology for necropsy details. Marshall, R., Sabiston, D. C., Allison, P. R., Bosman, A. R., and Dunnill, M. S. (1963). Immediate and late effects of pulmonary embolism by large thrombi in dogs. Thorax, 18, 1. Shapiro, R., and Rigler, L. G. (1948). Pulmonary embolism REFERENCES without infarction. Amer. J. Roentgenol., 60, 460. Arendt, J., and Rosenberg, M. (1959). Thromboembolism Short, D. S. (1951). A radiological study of pulmonary of the lungs. Amer. J. Roentgenol., 81, 245. infarction. Quart. J. Med., 20, 233. Barritt, D. W., and Jordan, S. C. (1961). Clinical features of Simon, G. (1970). Further observations on the long line pulmonary embolism. 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