PSP is rarer in the pediatric population than in adults. It generally occurs in tall, thin males aged 10–30 . In our study, the mean age was approximately 16 years. Smoking is implicated in the development of PSP, and the dangerous effect of tobacco has been recognized. Some authors highlighted that most adult patients (up to 75%)  with PSP were smokers, but in our study only one patient reported a smoking habit.
The etiology of PSP remains unclear. It is well accepted that PSP occurs from the rupture of blebs and bullae on the apex of the lung. The formation of these lesions is most likely multifactorial, including physical characteristics, anatomic abnormalities of the bronchial tree, genetic factors, and growth [13, 14]. Fujino and colleagues  suggested the hypothesis that growth during adolescence rapidly increases the vertical dimension of the thorax, causing an increase in negative pressure at the apex of the lung that may lead to formation of subpleural blebs or fluid-filled cysts with consequent pneumothorax upon rupturing. These lesions are not usually visible on X-ray but can often be detected using CT.
Diagnosis of PSP is generally clinical and confirmed by X-ray. In our study, like many others, CT was not usually performed at admission [16–18]. Some authors argue that finding blebs at CT, even if performed for other indications, is a strong indication for surgery . In contrast, most authors state that CT evidence of bullae does not necessarily predict outcomes, even if they agree that CT is an effective method to delineate the anatomical status of the bullae and bleb formation[20, 21]. Another consideration before undertaking CT scanning is the large amount of ionizing radiation involved.
In our study the biggest bleb size was 19 mm, while the average size was 4–5 mm. In all patients undergoing CT evaluation after a relapse, blebs and/or bullae were highlighted. However, the statistical analysis did not detect significance between recurrent episodes and lung injures (P = .08). Since the results showed no correlation between the presence of these lesions and the possibility of recurrence, there is no evidence that performing a CT scan on admission predicts future relapses. This supports our idea of reserving CT for cases of persistent air leak and relapse due to the high radiation dose involved in this imaging technique. Nonetheless, CT can assist in choosing the best therapeutic approach in selected cases.
The largest problem in PSP management is the lack of standardized guidelines. Consequently, PSP treatment is based on the experience of the individual surgery unit and evidence from the adult population. The main issues are choosing between observation alone with or without oxygen administration or chest drain insertion, and the correct timing for surgery. To date, the initial treatment approach is decided according to the size and symptoms at admission. The current management for small PSP is based on observation with oxygen administration in the majority of cases. By contrast, the presence of a large (≥ 2 cm) pneumothorax is the main indication for insertion of a chest drain. The therapeutic strategy used in our center for small PSP and clinically stable large PSP was simple observation. Despite this, the length of hospitalization of our patients was similar compared to patients treated with oxygen administration in other studies [1, 6, 9, 16]. These patients generally underwent chest X-ray within 3 days of hospitalization to check if the pneumothorax had been reduced in size and to determine the possibly of discharge. In case of failure of conservative treatment (in terms of increase in size and/or exacerbation of symptoms), we opted for the insertion of a chest drain. The LOS was longer in patients treated with chest drain insertion compared to those who were only observed (6.36 days vs. 2.4 days), and this appears to be in keeping with other studies [8, 16]. The longest LOS was related to surgery (10 days). Our statistical analysis showed that the LOS is linked to the therapeutic strategy (P = .001), confirming that it would be advisable to initially opt for a non-invasive treatment of observation alone in those patients with a small PSP and/or clinically stable to reduce the length of hospitalization.
Non-surgical management is still associated with a high failure rate. In our study, 27% of patients had an episode of relapse, but the incidence was even higher in other studies [1, 16]. The statistical analysis showed that the possibility of relapse was not associated with the initial treatment chosen (P = .24). This confirms that patients with small and/or clinically stable larger PSP may be treated with observation alone, reserving more invasive treatments for any clinical exacerbation, persistent air leak and/or relapse. VATS was first reported by Rodgers in 1986 for the treatment of secondary pneumothorax in children with cystic fibrosis . This surgical advancement has completely changed the approach to surgery for the treatment of PSP. Prior to VATS, traditional surgery involved high morbidity and mortality. However, VATS is considered a safe method with significantly reduced morbidity and mortality [1, 16, 23, 24]. In our study, surgery was required in 6 patients after an episode of relapse with a recurrence rate of 33%, slightly higher than reported by other studies (11–28%) [1, 14]. A recent survey of pediatric surgeons found that most respondents preferred chest tube insertion in the management of a first episode of PSP and performed surgery for a second episode, in the presence of bullae more than 2 cm in diameter, or for recurrent pneumothorax . Figure 1 shows the management flow-chart for PSP in our third level pediatric surgical ward.
Our study limitations include being retrospective and using a small cohort of patients. Prospective studies with a higher number of patients are encouraged to establish evidence-based guidelines for the treatment of PSP in the pediatric population.