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1
Department of Diagnostic Imaging, Chaim Sheba Medical Center, Sackler School
of Medicine, Tel-Aviv University, Tel Hashomer, 52621 Israel.
2
Department of Thoracic Surgery, Chaim Sheba Medical Center, Sackler School of
Medicine, Tel-Aviv University, Tel Hashomer, 52621 Israel.
3
Department of Diagnostic Imaging, Meir General Hospital, Sapir Medical Center,
Sackler School of Medicine, Tel-Aviv University, Israel.
Received November 20, 2000;
accepted after revision March 28, 2001.
Address correspondence to E. Konen.
Abstract
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MATERIALS AND METHODS. Available chest radiographs of 172 of 199 sequential patients who had undergone upper lobectomy in a university hospital were evaluated for the presence of a juxtaphrenic peak. The study included 98 cases with right upper lobectomy and 74 with left upper lobectomy. Radiographs were grouped in three postoperative periods: period I, within 7 days after lobectomy (n = 142); period II, between 8 and 30 days (n = 113); and period III, 31 days or more after lobectomy (n = 101). Four experienced radiologists in consensus determined the prevalence of the "juxtaphrenic peak sign," in relation to age, sex, side of lobectomy, positioning (erect or supine), presence of juxtadiaphragmatic abnormalities, and time interval since surgery.
RESULTS. The prevalence of the juxtaphrenic peak sign gradually increased from 40.6% in period I to 71.9% in period III after right upper lobectomy (p < 0.01), and from 19% to 47.7%, respectively, after left upper lobectomy (p < 0.01). Its overall prevalence was significantly higher after right upper lobectomy (58.2%) than after left upper lobectomy (40.5%) (p = 0.02), and on erect chest films (51.4%) than on supine ones (28.9%).
CONCLUSION. The prevalence of the juxtaphrenic peak sign increases gradually during the weeks following lobectomy. It is more frequent on erect films and after right upper lobectomy. The juxtaphrenic peak may serve as an additional useful radiologic sign suggesting upper lobectomy.
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The purpose of our study was to determine the prevalence of the juxtaphrenic peak in a large number of consecutive patients with upper lobectomy, as related to side of surgery, erect or supine positioning, and time elapsed since surgery.
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We reviewed all chest radiographs for the presence or absence of a juxtaphrenic peak, using the expanded criteria as defined by Kattan et al. [1]
...a small sharply defined shadow projecting upward from the medial half of the hemidiaphragm at or near the highest point of the dome. Its shape varies from that of a broad tent to a peak, steeple or spire.... A fine line...is sometimes seen extending toward the hilum from the apex of the peak.
For each radiograph, the following parameters were recorded: age, sex, side of lobectomy, positioning (erect or supine), presence of juxtadiaphragmatic parenchymal or pleural abnormalities, and time interval since surgery. Additionally, because progressive radiation fibrosis has been suggested as a cause of increasing prominence of juxtaphrenic peaks [3], the use of radiation therapy and its timing in relation to that of the chest radiograph was recorded for each patient.
In 86 of the 172 patients, a preoperative chest radiograph was available. These radiographs were used as a baseline for comparison with the postoperative studies of the same patients.
Available CT scans obtained before (n = 42) and after (n = 33) surgery were evaluated. CT scans were collimated at 10 mm in 69 patients; at 2.5 mm in three; and at 5.5, 8.8, and 13 mm in one patient each. Juxtadiaphragmatic structures including inferior accessory fissures were analyzed on the basis of a previous study [3].
All relevant chest radiographs found in our digital archieves were printed out before evaluation. All chest radiographs were studied for final interpretation by a consensus of four experienced radiologists. Before interpretation, all participating radiologists thoroughly reviewed the various shapes of the juxtaphrenic peak, as described in previous studies [1,2,3]. The data were recorded in a computer database. We performed statistical analyses using the chi-square test. A p value of less than 0.05 was regarded as significant.
To establish the specificity of the "juxtaphrenic peak sign" in upper lobectomy as opposed to lower lobectomy, chest radiographs of patients after lower lobectomy were also evaluated for the presence of a juxtaphrenic peak in a similar method as described previously. Between January 1995 and June 1999, 47 patients underwent lower lobectomy (28 right and 19 left), and 37 radiologic files of these patients were available. These files were randomly mixed with those of patients with upper lobectomy; the reviewers were unaware of the type of surgery to avoid bias.
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The juxtaphrenic peak sign was identified at least once in 74 (51.4%) of 144 patients with an available erect radiograph at any period, as opposed to 26 (28.9%) of 90 patients with a supine radiograph (p < 0.005). After eliminating from calculation patients with parenchymal consolidations or large pleural effusions, we identified the juxtaphrenic peak in 66 (62.9%) of 105 patients with an available erect radiograph, as opposed to 20 (39.2%) of 51 patients with a supine radiograph (p < 0.01).
Age, sex, and presence of juxtadiaphragmatic parenchymal or pleural abnormalities were found to have no statistically significant effect on the prevalence of the juxtaphrenic peak.
Twenty-nine of 172 patients had received radiation therapy in addition to surgery. The interval between lobectomy and radiation ranged between 30 and 1380 days, average 443 days. Only four chest radiographs included in our series were obtained after radiation, of which only one showed a new juxtaphrenic peak.
Multiple peaks were observed in 14 (8.1%) of the 172 patients, two peaks in 11 (Fig. 2A), and three peaks in three patients.
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Preoperative chest films were available in 86 patients, and a juxtaphrenic peak was identified in four of them. Upper lobe atelectasis due to tumor obstruction was identified in three of these four patients. A new juxtaphrenic peak appeared after lobectomy in 47 (57.3%) of the remaining 82 patients.
A preoperative CT scan was available in 42 patients, eight (19%) of whom had a recognizable inferior accessory fissure.
Postoperative CT scans were available in 33 patients. An inferior accessory fissure was identified in 12 (60%) of 20 patients after left upper lobectomy (a juxtaphrenic peak was shown on chest radiographs of six of these 12 patients) and in seven (53.8%) of 13 cases after right upper lobectomy (a juxtaphrenic peak was shown on chest radiographs of all seven patients) (Figs. 1B, 2B, and 2C). Revision of CT scans of the six patients after left upper lobectomy with no juxtaphrenic peak on their chest radiographs revealed the inferior accessory fissure to be obliquely oriented in all six (Fig. 3). Linear structures other than an inferior accessory fissure, previously described as "pleural cleft" or "medial septum" [3], were observed in another eight patients with a juxtaphrenic peak sign.
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In none of the chest radiographs of 37 patients obtained after lower lobectomy was a juxtaphrenic peak shown.
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The juxtaphrenic peak sign has previously been reported by several authors as an indirect sign of upper lobe volume loss [1,2,3,4,5]. Although Simon [4] described in 1965 a "vertical basal line" observed in upper lobe volume loss due to tuberculosis and after middle lobectomy, Kattan et al. [1, 5] first coined its name and described it as an additional indirect sign for upper lobe collapse. Their series included "about 30" random cases of upper lobe volume loss due to a variety of causes with no specification of its frequency. Since then, two additional studies [2, 3] investigated the origin of the juxtaphrenic peak sign, suggesting that it is mainly due to an inferior accessory fissure, with variable rates of incidence. Although Cameron [2] found a juxtaphrenic peak in eight (28%) of his 29 patients without specifying the rate for each side, Davis et al. [3] identified it in nine (75%) of 12 patients on the left and in 12 (71%) of 17 on the right. Both series were, however, limited to a relatively small number of nonconsecutive cases and included patients with upper lobe volume loss due to various reasons, including upper lobectomy.
Because lobectomy may be regarded as the purest form of volume loss, we agree with these authors and suggest that our findings regarding the prevalence of the juxtaphrenic peak, in relation to side, position, and time elapsed since lobectomy, can be applied to other causes of upper lobe volume loss. Furthermore, our study also supports previous observations [2, 3] that suggested that the inferior accessory fissure was a main cause for the appearance of a juxtaphrenic peak sign. We have identified a prominent inferior accessory fissure in 19 (57.6%) of 33 patients with an available postoperative CT scan, whereas in another eight cases, other linear opacities [3] appeared to account for the presence of a juxtaphrenic peak.
We found a significant increase in the prevalence of the juxtaphrenic peak with time elapsed since surgery. The reason for this is unclear. Kattan et al. [1] suggested a mechanism that may explain our observation: continuous negative pressure, such as that created by upper lobectomy, may cause a gradual protrusion of extrapleural fat into the retracted accessory fissure, thus rendering the fissure more visible on later chest radiographs. This same mechanism may explain another interesting finding in our study that showed that in eight (61.5%) of 13 cases with available CT scans before and after lobectomy, an accessory fissure was identified only after surgery. This finding was seen in one patient of the study by Davis et al. [3], who suggested that upper lobe volume loss might cause the upward traction of a "latent inferior accessory fissure" in some patients.
Because periodic chest radiography is an important part of the postoperative follow-up of patients after lobectomy, radiologists should be familiar with all radiologic signs that may be encountered after this operation and with their expected prevalence, including minor signs such as the juxtaphrenic peak. We found that a juxtaphrenic peak can be expected to appear on chest radiographs in about 70% of patients 1 month or more after right upper lobectomy and on 50% after left upper lobectomy. Conversely, we did not find a juxtaphrenic peak on any of the chest radiographs of 37 patients who underwent lower lobectomy. These findings suggest that the presence of a juxtaphrenic peak on follow-up chest radiographs of patients after thoracic surgery is highly suggestive of upper lobectomy. The juxtaphrenic peak sign may be helpful to radiologists, especially in cases in which the clinical history of the patient is incomplete.
We have found the juxtaphrenic peak to be significantly more prevalent after right upper lobectomy as compared with the left. This finding could be explained by an autopsy report from 1900 by Dévé [6], who found that the right inferior accessory fissure were deeper and more complete than those on the left side; thus, these features perhaps render the right inferior fissures more visible on chest radiographs. Another explanation could be our finding that accessory fissures have a higher tendency to be obliquely oriented after left upper lobectomy than after right upper lobectomy (6/12 vs 0/7, respectively), perhaps because of left-sided cardiac deviation, thus with no component that would be tangential to the X-ray beam on posteroanterior or anteroposterior views (Fig. 3).
The prevalence of a juxtaphrenic peak on erect as compared with supine radiographs was significantly higher, even after eliminating potentially influencing factors such as consolidations or large pleural effusions. Changes in orientation of the inferior accessory fissure and other basal linear opacities caused by changes in positioning may explain our findings. A similar inconsistency of the juxtaphrenic peak sign due to orientation changes was observed by Kattan et al. [1], who mentioned one case in their series in which the juxtaphrenic peak sign disappeared during expiratory films and that "occasionally, additional studies, such as oblique views...or fluoroscopy are required" to show this sign.
Davis et al. [3] suggested that the relatively high frequency of juxtaphrenic peaks in their series may be due to radiation therapy administered to some patients. Although the prevalence of juxtaphrenic peak in our series is comparable to that of Davis et al., we found only one case of 172 in which radiation could have had any impact on the appearance of a juxtaphrenic peak. It seems that the relatively high prevalence of juxtaphrenic peaks in both series is a direct result of upper lobe volume loss, with only little effect of radiation.
A juxtaphrenic peak may be encountered in healthy subjects as previously mentioned [1]. A preoperative chest radiograph was available in 86 patients of our series, four of whom showed a juxtaphrenic peak: three peaks were associated with upper lobe collapse. In 47 of the remaining 82 cases, a juxtaphrenic peak appeared after upper lobectomy. This finding suggests a direct connection between the appearance of a juxtaphrenic peak and upper lobectomy.
A limitation of our study is that it is retrospective. Although we found a relevant radiologic file in 172 (86%) of 199 consecutive patients who underwent upper lobectomy, we could not find a radiograph for each of the three postoperative periods in many cases. We believe, however, that the large number of radiographs available for each period and the fact that our series includes an unselected population of consecutive patients provide statistical strength and reliability. Another disadvantage of a retrospective study is the partially missing clinical data, such as the degree of chronic lung disease, which may influence the prevalence of the juxtaphrenic peak in some patients.
We conclude that the juxtaphrenic peak sign is a frequent finding on chest radiographs of patients after upper lobectomy. Its prevalence gradually increases during the weeks after surgery, and it is more frequent on the right and on erect radiographs. It may serve as an additional useful sign suggesting upper lobectomy.
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