Diagnostic Radiology
Clearing Patterns of Pulmonary Infarction and Slowly Resolving Pneumonia 1 Alan S. Hendin, M.D. Previous authors have suggested that the radiographic clearing pattern of pulmonary infarction is specific and permits differentiation from pneumonitis. Pulmonary infarcts are said to " shrink" or " melt" and pneumonitis consolidations to clear diffusely. Chest radiographs of 4 patients with angiographically conf irmed pulmonary infarction and 5 with slowly resolving pneumonitis were examined, in random case order , by three independent radiologists unaware of the diagnoses. All observers found the shrinking pattern in 3 of the 4 cases of pulmonary infarction and in 1 case of pneumonitis. The shrinking pattern Is not specific for pulmonary infarction; it may be related to fibrotic organization of pulmonary consolidation. INDEX TERMS:
Lungs, infarction. Pneumonia. Pneumonitis
Radiology 114:557-559, March 1975
pneumonia. Pulmonary infarcts are said to contract or shrink, while pneumonias dissolve diffusely or clear irregularly. In the most recent report, the term " melting sign" was coined for this shrinking pattern (8). The present study was designed to test the sensitivity and specificity of the shrinking or melting pattern in pulmonary infarction. Chest radiographs of patients with angiographically confirmed pulmonary infarction and of patients with slowly resolving , infectious pneumonia were examined for the pattern of clearing by radiologists unaware of the diagnoses.
the characteristic chest abnormalities of pulmonary infarction are generally nonspecific. Abnormalities encountered on physical examination, the electrocardiogram, blood gas and serum enzyme determinations, and perfusion lung scan are also nonspecific. Diagnosis usually requires correlat ion of findings from these examinat ions and clinical judgement. Pulmonary angiography is the most specific diagnostic procedure for acute pulmonary embolic disease but, because of its inherent risks and awkwardness, it is not performed on most patients with pulmonary infarction. Continued search for more specific noninvasive diagnostic modalities is justified by the frequency and clinical importance of pulmonary embolic disease. Other investigators (2, 5, 8) have suggested that differences in clearing patterns of pulmonary consolidation may reliably differentiate pulmonary infarction from
Review of 78 pulmonary arteriograms obtained in our department between 1 January 1970 and 28 February
A
c
R
ADIOGRAPHICALLY,
B
METHODS
Pulmonary Infarction
D
Fig. 1. A through D. Sequential radiographs of a pulmonary infarct in the right lower lobe (obtained September 3, 4, 5 and 11, 1970). Pulmonary angiograms demonstrated a clot in the right lower lobe artery .
1
From the Department of Radiology, University of California School of Medicine, San Francisco, Calif. Accepted for publication in August
1974. Supported in part by National Institutes of Health Training Grant GM 01272 from the National Institute of General Medical Science.
557
shan
558
ALAN S. HENDIN
March 1975
Fig. 2. A through D. Pneumonitis due to psittacosis in the left upper lobe (sequential radiographs obtained June 14, 18 and 28, 1971 and July 2, 1971). A four-fold change in psittacosis titers occurred . and no bacterial pathogen was recovered from the sputum. The pulmonary angiogram showed no emboli.
1972 provided 18 cases of proved emboli. All the following criteria were required for the case to be considered thromboembolic pulmonary infarction: (a) Radiographically defined pulmonary consolidation (not obscured by pleural effusion) (b) One or more angiographically demonstrated discrete emboli to the segmental or lobar artery supplying the consolidated region (e) Absence of purulent sputum, absence of bacteremia, no pathogens cultured from sputum (d) Four sequential chest radiographs of good quality (to observe the stages of clearing). Among the 18 cases, 14 had definable consolidation, and 5 of these had at least four satisfactory frontal chest radiographs obtained during the process of clearing. One of these was excluded because of Pseudomonas bacteremia associated with purulent sputum and cavitation in the infarcted area.
All radiologists considered the same 3 of 4 pulmonary infarcts to have melted, and all considered the fourth infarct to have cleared irregularly (Fig. 1). All considered the same one of the pneumonitis consolidations to have melted (Fig. 2). Two radiologists considered a second pneumonitis consolidation to have melted (Fig. 3). Unanimous agreement occurred in 8 of the 9 cases.
Infectious Pneumonia
DISCUSSION
Review of admissions to two medical wards for one year provided 5 cases of slowly resolving pneumonia, as chosen by all of the following criteria: (a) Two or more sputum or blood cultures positive for a predominant bacterial pathogen, or fourfold change in serum antibody titer for a viral infection (b) Pulmonary consolidation requiring over 21 days to disappear (c) No clinical evidence of thromboembolic disease, or a pulmonary arteriogram was negative for emboli (d) Four sequential frontal chest radiographs of like quality (to observe stages of clearing).
Although three separate articles (2, 5, 8) on the radiography of pulmonary infarction have suggested the possible usefulness of the shrinking or melting pattern , no prospective or retrospective comparison of clinically proved infarctions and pneumonias has been published. Strict adherence to the diagnostic criteria of this study resulted in a relatively small number of cases for comparison. In every case of infarction, angiograms demonstrated emboli in the arteries supplying the consolidated lung and coexistent pulmonary infection was not evident. The choice of slowly resolving pneumonitis excluded cases with transient pulmonary Infiltrate{s) and many pneumonitis cases that resolved within three weeks or
For each case in the study, the four frontal chest radiographs were coded and numbered chronologically. All names and dates were covered and the cases arranged randomly. Three radiologists, unfamiliar with the cases and unaware of the diagnosis, examined the radiographs of each case, independently. The radiologists stated (a) whether clearing occurred and (b) whether clearing was diffuse or occurred by shrinking (melting). RESULTS
Vol. 114
PULMONARY INFARCTION AND SLOWLY RESOLVING PNEUMONIA
559
Diagnostic RadIology
Fig. 3. A through D. Sequential radiographs (obtained March 13, 20 and 23, 1972 and April 7, 1972) showing pneumococcal pneumonia superinfected with Klebsiella pneumoniae (proved by cultures of bronchial washings).
for which follow-up radiographs were not available . Patients who died of their illness within three weeks were excluded. The average duration of abnormal pulmonary density was 36 days (range 22 to 47 days) for slowly resolving pneumonitis cases , compared to 50 days (range 8 days to 5 months) for cases of pulmonary infarction. Causative agents of the pneumonias included Diplococcus pneumoniae (2 cases), Hemophilus influenzae, Klebsiella pneumoniae, and psittacosis . Although only one of the pneumonia patients underwent pulmonary angiography (Fig. 2), the diagnoses were established by generally accepted clinical criteria (7). The usefulness of any radiographic sign depends on the ability of different observers to recognize it. Our study shows that the changing shape of a pulmonary infiltrate is subject to observer variation . All observers concurred that the shrinking pattern occurred in 3 of the 4 cases of pulmonary infarction, and in the one pneumonitis case angiographically negative for emboli. This indicates that the shrinking pattern is not specific for pulmonary infarction. Because our series was small, the overall frequency of the pattern was not determined . The pattern of shrinking or melting of complete pulmonary infarction is possibly related to the fibrotic organization of the infarct. This process begins at the periphery of the infarct during the second week and progresses to involve the entire zone, with subsequent shrinkage (4). Some pneumonia consolidations also organize by fibroblastic proliferation, involving fibrin plugs in the exudate . Connective tissue proliferation varies in extent and may extend into the pores of Kohn (1, 3, 6). It can progress to produce homogeneous nodular masses, which
radiographically resemble pulmonary neoplasms-localized organizing pneumonias (1). Fibrotic organization and contraction may account for the observed instances of melting or shrinking in the consolidations of slowly resolving pneumonia . ACKNOWLEDGMENT: I wish to thank Drs. Granville C. Coggs , Morton G. Glickman, and Fred l. Stargardter for their participation in evaluating the chest radiographs in this series .
Department of Radiology. 380-M University of California School of Medicine San Francisco. Calif. 94143
REFERENCES 1. Ackerman LV. Elliott GV. Alanis M: Localized organizing pneumonia : its resemblance to carcinoma . A review of its clinical. roentgenographic and pathologic features . Am J Roentgenol 71: 988-996. Jun 1954 2. Fisher MS: Pulmonary embolism . Med Radiogr Photogr 46: 53-75, 1970. 3. Floyd R: Organizat ion of pneumonic exudates . Am J Med Sci 163:5 27-548, Apr 1922 4. Hampton AO. Castleman B: Correlat ion of postmortem chest teleroentgenograms with autopsy findings with special reference to pulmonary embolism and infarction . Am J Roentgenol 43:305 -326. Mar 1940 5. Jellen J: The roentgenological manifestations of pulmonary embol ism with infarction of the lung. Am J Roentgenol 41:901-908. Jun 1939 6. McCrae T: Delayed resolution in lobar pneumonia . Johns Hopkins Hosp Reports 15:277-305.1910 7. Tillotson JR, Lerner AM: Pneumonias caused by gram negative bacilli . Medicine (Bait) 45:65-76. Jan 1966 8. Weesner ME. Sanders I, White GW: The melting sign in resolving transient pulmonary infarction. Am J Roentgenol 111:782790 . Apr 1971
Clearing Patterns of Pulmonary Infarction and Slowly Resolving Pneumonia 1 Alan S. Hendin, M.D. Previous authors have suggested that the radiographic clearing pattern of pulmonary infarction is specific and permits differentiation from pneumonitis. Pulmonary infarcts are said to " shrink" or " melt" and pneumonitis consolidations to clear diffusely. Chest radiographs of 4 patients with angiographically conf irmed pulmonary infarction and 5 with slowly resolving pneumonitis were examined, in random case order , by three independent radiologists unaware of the diagnoses. All observers found the shrinking pattern in 3 of the 4 cases of pulmonary infarction and in 1 case of pneumonitis. The shrinking pattern Is not specific for pulmonary infarction; it may be related to fibrotic organization of pulmonary consolidation. INDEX TERMS:
Lungs, infarction. Pneumonia. Pneumonitis
Radiology 114:557-559, March 1975
pneumonia. Pulmonary infarcts are said to contract or shrink, while pneumonias dissolve diffusely or clear irregularly. In the most recent report, the term " melting sign" was coined for this shrinking pattern (8). The present study was designed to test the sensitivity and specificity of the shrinking or melting pattern in pulmonary infarction. Chest radiographs of patients with angiographically confirmed pulmonary infarction and of patients with slowly resolving , infectious pneumonia were examined for the pattern of clearing by radiologists unaware of the diagnoses.
the characteristic chest abnormalities of pulmonary infarction are generally nonspecific. Abnormalities encountered on physical examination, the electrocardiogram, blood gas and serum enzyme determinations, and perfusion lung scan are also nonspecific. Diagnosis usually requires correlat ion of findings from these examinat ions and clinical judgement. Pulmonary angiography is the most specific diagnostic procedure for acute pulmonary embolic disease but, because of its inherent risks and awkwardness, it is not performed on most patients with pulmonary infarction. Continued search for more specific noninvasive diagnostic modalities is justified by the frequency and clinical importance of pulmonary embolic disease. Other investigators (2, 5, 8) have suggested that differences in clearing patterns of pulmonary consolidation may reliably differentiate pulmonary infarction from
Review of 78 pulmonary arteriograms obtained in our department between 1 January 1970 and 28 February
A
c
R
ADIOGRAPHICALLY,
B
METHODS
Pulmonary Infarction
D
Fig. 1. A through D. Sequential radiographs of a pulmonary infarct in the right lower lobe (obtained September 3, 4, 5 and 11, 1970). Pulmonary angiograms demonstrated a clot in the right lower lobe artery .
1
From the Department of Radiology, University of California School of Medicine, San Francisco, Calif. Accepted for publication in August
1974. Supported in part by National Institutes of Health Training Grant GM 01272 from the National Institute of General Medical Science.
557
shan
558
ALAN S. HENDIN
March 1975
Fig. 2. A through D. Pneumonitis due to psittacosis in the left upper lobe (sequential radiographs obtained June 14, 18 and 28, 1971 and July 2, 1971). A four-fold change in psittacosis titers occurred . and no bacterial pathogen was recovered from the sputum. The pulmonary angiogram showed no emboli.
1972 provided 18 cases of proved emboli. All the following criteria were required for the case to be considered thromboembolic pulmonary infarction: (a) Radiographically defined pulmonary consolidation (not obscured by pleural effusion) (b) One or more angiographically demonstrated discrete emboli to the segmental or lobar artery supplying the consolidated region (e) Absence of purulent sputum, absence of bacteremia, no pathogens cultured from sputum (d) Four sequential chest radiographs of good quality (to observe the stages of clearing). Among the 18 cases, 14 had definable consolidation, and 5 of these had at least four satisfactory frontal chest radiographs obtained during the process of clearing. One of these was excluded because of Pseudomonas bacteremia associated with purulent sputum and cavitation in the infarcted area.
All radiologists considered the same 3 of 4 pulmonary infarcts to have melted, and all considered the fourth infarct to have cleared irregularly (Fig. 1). All considered the same one of the pneumonitis consolidations to have melted (Fig. 2). Two radiologists considered a second pneumonitis consolidation to have melted (Fig. 3). Unanimous agreement occurred in 8 of the 9 cases.
Infectious Pneumonia
DISCUSSION
Review of admissions to two medical wards for one year provided 5 cases of slowly resolving pneumonia, as chosen by all of the following criteria: (a) Two or more sputum or blood cultures positive for a predominant bacterial pathogen, or fourfold change in serum antibody titer for a viral infection (b) Pulmonary consolidation requiring over 21 days to disappear (c) No clinical evidence of thromboembolic disease, or a pulmonary arteriogram was negative for emboli (d) Four sequential frontal chest radiographs of like quality (to observe stages of clearing).
Although three separate articles (2, 5, 8) on the radiography of pulmonary infarction have suggested the possible usefulness of the shrinking or melting pattern , no prospective or retrospective comparison of clinically proved infarctions and pneumonias has been published. Strict adherence to the diagnostic criteria of this study resulted in a relatively small number of cases for comparison. In every case of infarction, angiograms demonstrated emboli in the arteries supplying the consolidated lung and coexistent pulmonary infection was not evident. The choice of slowly resolving pneumonitis excluded cases with transient pulmonary Infiltrate{s) and many pneumonitis cases that resolved within three weeks or
For each case in the study, the four frontal chest radiographs were coded and numbered chronologically. All names and dates were covered and the cases arranged randomly. Three radiologists, unfamiliar with the cases and unaware of the diagnosis, examined the radiographs of each case, independently. The radiologists stated (a) whether clearing occurred and (b) whether clearing was diffuse or occurred by shrinking (melting). RESULTS
Vol. 114
PULMONARY INFARCTION AND SLOWLY RESOLVING PNEUMONIA
559
Diagnostic RadIology
Fig. 3. A through D. Sequential radiographs (obtained March 13, 20 and 23, 1972 and April 7, 1972) showing pneumococcal pneumonia superinfected with Klebsiella pneumoniae (proved by cultures of bronchial washings).
for which follow-up radiographs were not available . Patients who died of their illness within three weeks were excluded. The average duration of abnormal pulmonary density was 36 days (range 22 to 47 days) for slowly resolving pneumonitis cases , compared to 50 days (range 8 days to 5 months) for cases of pulmonary infarction. Causative agents of the pneumonias included Diplococcus pneumoniae (2 cases), Hemophilus influenzae, Klebsiella pneumoniae, and psittacosis . Although only one of the pneumonia patients underwent pulmonary angiography (Fig. 2), the diagnoses were established by generally accepted clinical criteria (7). The usefulness of any radiographic sign depends on the ability of different observers to recognize it. Our study shows that the changing shape of a pulmonary infiltrate is subject to observer variation . All observers concurred that the shrinking pattern occurred in 3 of the 4 cases of pulmonary infarction, and in the one pneumonitis case angiographically negative for emboli. This indicates that the shrinking pattern is not specific for pulmonary infarction. Because our series was small, the overall frequency of the pattern was not determined . The pattern of shrinking or melting of complete pulmonary infarction is possibly related to the fibrotic organization of the infarct. This process begins at the periphery of the infarct during the second week and progresses to involve the entire zone, with subsequent shrinkage (4). Some pneumonia consolidations also organize by fibroblastic proliferation, involving fibrin plugs in the exudate . Connective tissue proliferation varies in extent and may extend into the pores of Kohn (1, 3, 6). It can progress to produce homogeneous nodular masses, which
radiographically resemble pulmonary neoplasms-localized organizing pneumonias (1). Fibrotic organization and contraction may account for the observed instances of melting or shrinking in the consolidations of slowly resolving pneumonia . ACKNOWLEDGMENT: I wish to thank Drs. Granville C. Coggs , Morton G. Glickman, and Fred l. Stargardter for their participation in evaluating the chest radiographs in this series .
Department of Radiology. 380-M University of California School of Medicine San Francisco. Calif. 94143
REFERENCES 1. Ackerman LV. Elliott GV. Alanis M: Localized organizing pneumonia : its resemblance to carcinoma . A review of its clinical. roentgenographic and pathologic features . Am J Roentgenol 71: 988-996. Jun 1954 2. Fisher MS: Pulmonary embolism . Med Radiogr Photogr 46: 53-75, 1970. 3. Floyd R: Organizat ion of pneumonic exudates . Am J Med Sci 163:5 27-548, Apr 1922 4. Hampton AO. Castleman B: Correlat ion of postmortem chest teleroentgenograms with autopsy findings with special reference to pulmonary embolism and infarction . Am J Roentgenol 43:305 -326. Mar 1940 5. Jellen J: The roentgenological manifestations of pulmonary embol ism with infarction of the lung. Am J Roentgenol 41:901-908. Jun 1939 6. McCrae T: Delayed resolution in lobar pneumonia . Johns Hopkins Hosp Reports 15:277-305.1910 7. Tillotson JR, Lerner AM: Pneumonias caused by gram negative bacilli . Medicine (Bait) 45:65-76. Jan 1966 8. Weesner ME. Sanders I, White GW: The melting sign in resolving transient pulmonary infarction. Am J Roentgenol 111:782790 . Apr 1971
