Is There a Role for Chest Computed Tomography in Patients with Primary Spontaneous Pneumothorax ?

Background: Primary spontaneous pneumothorax is a relatively common condition in young adults. Although blebs and bullae are frequently found in patients with primary spontaneous pneumothorax, they are very rarely the actual cause of the pneumothorax. Objective: To assess our experience with chest computed tomography evaluation in patients with recurrent spontaneous pneumothorax as compared to their histopathology findings. Study Design: A prospective study analysis. Materials and Methods: From January 2013 to December 2016, 38 consecutive patients with unilateral recurrent spontaneous pneumothorax underwent video-assisted thoracic surgery. Their chest computed tomography scans were reviewed and compared with their histopathology findings. Results: Thirty-six adult patients with unilateral recurrent spontaneous pneumothorax were included; their mean age was 33.9 years, and they all received video-assisted thoracic surgery and mechanical pleurodesis. Blebs or bullae were present in the chest computed tomography scans of fourteen patients (39%); of those fourteen patients, five (35.7%) had emphysematous changes in histopathology. Seventeen out of the thirty-six (47%) had no blebs or bullae in their chest computed tomography scans; of those seventeen patients, ten (59%) had emphysema like changes and seven (41%) had blebs in their histopathology studies. The remaining five patients (14%) had normal chest computed tomography scans. Conclusions: We conclude that preoperative chest computed tomography is not beneficial in every patient with recurrence of primary spontaneous pneumothorax.


Introduction
Primary spontaneous pneumothorax is a relatively common condition in otherwise healthy young adults.The typical patient is young, thin, tall, a cigarette smoker, and has acute chest pain with varying degrees of cough and shortness of breath.
The reported incidence of primary spontaneous pneumothorax ranges between "8 and 28 cases per 100,000 per year for men and 1.2 to 6 cases per 100,000 per year for women [1] [2] [3]".Several studies have reported that chest computed tomography is a useful diagnostic method for the identification of blebs and bullae [4] [5].Reports have shown that patients with blebs and bullae have a greater risk of pneumothorax than patients without blebs and bullae [6] [7].
Other studies have suggested that pulmonary chest tomography findings (the number and size of blebs and bullae) can predict recurrence of pneumothorax [8].The aim of this study is to assess our experience of chest computed tomography in recurrence of primary spontaneous pneumothorax compared to histopathology findings.

Materials and Methods
This prospective study was performed at our institution between January 2013 and December 2016.This study was approved by the local ethics committee, which waived the need for written informed consent.Thirty-six patients [6 women (17%), mean age 32.3 years, 30 men (83%); mean age 32.1 years] with unilateral primary spontaneous pneumothorax underwent video-assisted thoracic surgery and mechanical pleurodesis (n = 36).Preoperative patient demographic data are presented in (Table 1).

Inclusion Criteria
All thirty-eight patients admitted with recurrence of unilateral spontaneous based on the evidence of their chest X-rays.

Initial Management
All the patients were initially managed in the emergency department and received thoracic drainage with chest tube size 28 French (F).Suction was added on first resort.

Chest Computed Tomography Scans
During hospitalization, all the patients had high-resolution computed tomography scans of the chest, with slice thickness of five millimeters.The scans were interpreted by different experienced radiologists.Blebs were defined as less than one centimeter in diameter, bullae as more than one centimeter in diameter (Figure 1).

Surgical Management
All patients received video-assisted thoracic surgery, which was performed in the apical segment of the upper lobe and the superior segments of the lower lobe, was inspected for blebs and bullae.These were resected with a 45 -60-millimeter Endo GIA™ (Covedien, Massachusetts, USA).If no blebs or bullae were visible in the lung parenchyma, a blinded resection of the apical segment was performed.The parietal pleural surface was abraded with a scratch pad.A single chest tube size 28 F was inserted and brought out through the camera port.It was then secured to the chest wall and connected to an underwater seal suction with negative pressure of −20 cm H 2 O.The chest tube was removed when there was no air leak.The surgical specimens were analyzed by different experienced pathologists.It must be emphasized that this histopathology study was conducted on the apices of lung specimens

Patient Follow-Up
All thirty-six patients were followed up at 6-month intervals in our outpatient clinic over a period of 36 months.At each visit, a chest X-ray was performed.

Statistical Analysis
Statistical analysis was performed using a chi-squared test.The continuous variables were expressed as the mean ± SD.A P value < 0.05 was considered statistically significant.

Results
The clinical data of the thirty-six patients seen in our institution are summarized in (Table 1).There were thirty men (83%) and six women (17%).The mean age of the patients was 33.9 years.About 64% of the patients were smokers.Left-sided spontaneous pneumothorax was identified in twenty-two patients (61%), and right-sided spontaneous pneumothorax was seen in fourteen patients (39%).Of the thirty-six patients, fourteen (39%) were found on a preoperative computed tomography scan to have lung blebs with emphysema like changes.Thus, the sensitivity of computed tomography in the detection of blebs in patients with primary spontaneous pneumothorax was 56%, with positive predictive value of 64% and negative predictive value of 59% (Table 2).

Discussion
There is some controversy surrounding the etiology of primary spontaneous pneumothorax.The accepted hypotheses are as follows: first, rupture of a dystrophic apical lesion, known as emphysematous changes [9]; second, air leakage known as "pleural porosity", following peripheral airway inflammation [10], with breakdown of alveoli, air dissection along the interstitium, and containment under the visceral pleura.Smoking has been implicated in the etiological pathway: a smoking habit is associated with a 12% risk of developing pneumothorax, compared to 0.1% in nonsmokers [2].The negative pressure gradient of the pleura increases from the base of the lung to the apex, with the result that the alveoli in the apex are subject to higher distending pressure than those at the base of the lung [11].
In surgical studies, Baronofsky et al. reported that diffuse subpleural bullae predominantly involve lung apices [12].However, resection of bullae or blebs and dystrophic apical lesion is highly recommended to prevent recurrence.In our study, there was no postoperative recurrence.Of 32 international pneumothorax experts, 85% recommend recurrence prevention after a second occurrence of primary spontaneous pneumothorax.Thoracoscopic surgical resection and parietal pleural abrasion to prevent primary spontaneous pneumothorax are highly recommended.
The frequency of identifying blebs or bullae in chest computed tomography varies.Guimeraes et al. found apical blebs on 28% of primary spontaneous pneumothorax chest computed tomography scans and no blebs on the computed tomography scans of 29 matched controls [13].Studies have shown that more than 80% of scanned patients, and as many as 79% of patients who have undergone surgical evaluation, have emphysematous changes [14] [15].Warner et al. conducted a prospective study on 26 patients who had had computed tomography scans [5].They showed that blebs and bullae were correlated with recurrence.
Sihoe et al. investigated the importance of computed tomography of the chest in selecting patients for prophylactic surgery in order to prevent contralateral recurrence [16].Contrary to these findings, Ouanes-Besbes et al. could not demonstrate a correlation between computed tomography-based dystrophy severity scoring and recurrence [17].
In our study, we found fourteen patients (39%) had blebs or bullae on their preoperative computed tomography scan, only, five of whom (35.7%) had emphysema like changes as compared to histopathology finding.Seventeen out of thirty-six patients (47%) had no blebs or bullae on their preoperative computed tomography.Ten patients (59%) had emphysematous changes, and seven patients (41%) had blebs in their histopathology findings.All patients had surgical resection with mechanical pleurodesis.We observed that all patients benefited from surgery, and there was no postoperative recurrence.

Conclusion
Therefore, based on our data, we conclude that this subset of patients should receive video-assisted thoracic surgical resection.We do not recommend routine preoperative computed tomography of the chest in patients with recurrence of primary spontaneous pneumothorax.
A. Calculated using independent two-sample t-test.B. Calculated using independent two-sample t-test on log scale.Other results calculated using Wilcox on signed-rank test.Surgical Science pneumothorax were included in the study.The diagnosis of pneumothorax was

Table 2 .
Comparison between CT scans and histopathology findings.
Subsequent surgery histopathology revealed blebs or bullae in 41% of the patients, despite prior normal computed tomography.The preoperative computed tomography scans appeared to have positive predictive value of 64% and negative predictive value DOI: 10.4236/ss.2017.810047434 Surgical Science of 59%.The limitations of our study are sample size and challenge of computed tomography interpretation.