Buffalo chest after minimally invasive repair of pectus excavatum for pectus excavatum: results of the Chest Wall International Group (CWIG) survey

Introduction

Buffalo chest (BC) is an anatomical condition characterized by a communication between the two pleural cavities. Historically, this phenomenon was observed in buffalo and reportedly recognized by North American Native populations, who could fatally wound these animals with a single chest injury—likely inducing a bilateral pneumothorax. In humans, a bilateral pneumothorax due to iatrogenic BC has been occasionally reported in the literature following sternotomy or other thoracic surgeries (1). Minimally invasive repair of pectus excavatum (MIRPE), introduced by Donald Nuss in 1998, has become the most widely used surgical technique for pectus excavatum (PE) repair in adolescent and young adult patients, with an estimated number of procedures of 2,500 per year from a 2015 Chest Wall International Group (CWIG) report (2,3). During MIRPE, retrosternal mediastinal dissection is performed to create a tunnel for the insertion of one or more metal bars. This results in opening the pleura on both sides, creating a communication between pleural cavities and establishing iatrogenic BC (4). While generally inconsequential, BC represents a potential risk factor for life-threatening events when a sudden unilateral spontaneous pneumothorax (SP), not related to the thoracoscopic procedure and suspected to result from the rupture of subpleural blebs, becomes bilateral, leading to significant respiratory compromise. Despite the high volume of PE repairs performed worldwide, bilateral SP cases following MIRPE have been very rarely documented (4).

SP is reported with an annual incidence ranging from 15.5 to 22.7/100,000. Considering the significant prevalence of subpleural blebs in PE patients—reported at 26.5%—and their 7.83-fold increased risk of SP compared to non-PE individuals, we hypothesize that BC after MIRPE may represent an underreported risk for severe complications (5-7). To assess surgeons’ awareness of BC and its potential clinical implications, we designed a survey on PE surgery, including BC management, and submitted it to all members of the CWIG, an international organization of thoracic and pediatric surgeons specialized in PE repair. We present this article in accordance with the SURGE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2287/rc).

Methods

An online survey including 29 items on pre-, intra-, and post-operative management of patients with PE was distributed via email to all surgeons affiliated with the CWIG. The survey questions were developed by MT and approved by MMF and ML. To increase the response rate, the survey was available between March and September 2024. The approximate completion time was approximately 10 minutes, and no incentives were offered. Figure 1 presents the survey questions and responses. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Informed consent was obtained from all individual participants.

Figure 1 Questions and answers of the CWIG survey. CT, computed tomography; CWIG, Chest Wall International Group; MIRPE, minimally invasive repair of pectus excavatum; MRI, magnetic resonance imaging; PE, pectus excavatum; SP, spontaneous pneumothorax.

Results

A total of 62 surgeons affiliated with CWIG participated in the survey. The majority of respondents were pediatric surgeons; therefore, the data primarily reflect pediatric patients. The response rate was 90.9%. Among them, 16% had fewer than 5 years of experience in PE surgery, 18% had between 6 and 11 years, while 66% had over 10 years of experience. Altogether, they perform an estimated number of more than 1,600 MIRPE per year.

In Figure 2, the main results of the survey are shown. Despite the expertise of the respondents, almost half of them had never heard about BC and more than 50% (33 surgeons) reported never having observed SP—either unilateral or bilateral—in their patients. The occurrence of unilateral SP (reported by 42% of surgeons) was more common than the observation of bilateral SP (reported by 18% of surgeons).

Figure 2 The main results of the survey. (A) How many MIRPEs do you perform per year? (B) Do you routinely perform CT scan before surgery? (C) Have you ever heard about “iatrogenic BC” after MIRPE? (D) In some of your patients operated for MIRPE, did you observe unilateral SP after MIRPE? (E) Which symptoms did patients with unilateral SP present? (F) In some of your patients operated for MIRPE, did you observe bilateral SP after MIRPE (not related to surgical factors)? (G) Which symptoms did patients with bilateral SP present? (H) Do you search for lung blebs with CT scan in patients with PE before surgery? (I) Do you search for lung blebs thoracoscopically in patients with PE during surgery? (J) Do you warn the patient and family about the risk of bilateral SP after MIRPE during informed consent? (K) Do you think bilateral SP after MIRPE is an under-evaluated risk? BC, Buffalo chest; Chest P, chest pain; CT, computed tomography; Lost of C, lost of Consciousness; Mild D, mild dyspnea; MIRPE, minimally invasive repair of pectus excavatum; PE, pectus excavatum; Severe D, severe dyspnea; SP, spontaneous pneumothorax.

A total of 93 cases of unilateral SP were reported, with six surgeons reporting more than five cases and two surgeons reporting more than 10 cases (13 and 20 cases, respectively). Of the 26 surgeons who reported cases of unilateral SP, 81% (21 surgeons) with more than 10 years of experience reported 86 cases, while five with fewer than 10 years of experience reported only seven cases. Bilateral SP was reported in 19 cases: seven surgeons with more than 10 years of experience reported 16 cases, while three surgeons with less than 10 years of experience reported one case each.

The number of bars implanted did not correlate with unilateral SP, which occurred similarly in patients with a single bar (45%) and in those with multiple bars (55%). Differently, bilateral SP occurred more frequently in patients with multiple bars (71%) compared to those with single bar (29%). Most unilateral (82%) and bilateral (78%) SP occurred within the first year post-surgery. Specifically, 50% of the unilateral SP cases and 45% of bilateral SP of the first year occurred within the first month. The remaining 18% unilateral SP observed beyond the first 1 year from MIRPE occurred in two cases after 1 year, in one case after 2 years, and in one case after 3 years. The remaining 22% of bilateral SP observed beyond 1 year from MIRPE occurred at 13 months.

Symptoms of unilateral and bilateral SP are shown in Figure 2E,2G. As expected, the symptoms of bilateral SP were more severe, and included death in one case.

Computed tomography (CT) scans were the preferred pre-operative imaging technique, routinely used by 65% of respondents, whereas magnetic resonance imaging (MRI) is used by only 19%. Interestingly, seven surgeons do not utilize either CT or MRI, and three reported using both.

Regarding lung bleb detection, though CT scan was the preferred pre-operative radiologic evaluation, only 33% of the surgeons search for lung blebs routinely using CT scans, and 13% search for blebs only in specific cases, such as in patients with a history of SP or a Marfanoid phenotype.

During thoracoscopy, 53% of the surgeons do not search for lung blebs. Among the others, 13% examine only the right lung, 13% check both lungs and 20% search for blebs only in specific cases, predominantly if there is evidence of blebs on the CT or if there is a history of blebs or SP. Only 18% would search for blebs in Marfanoid phenotype patients.

If lung blebs are detected on CT scans, 59% surgeons would perform thoracoscopic blebectomy, and 34% of them would also add pleurodesis. However, 41% would prefer conservative management (observation). Instead, if surgery has been chosen to treat blebs, 80% of respondents would do it during MIRPE, 13% before, and 7% after MIRPE.

There was no consensus among the respondent surgeons about the communication of the risk of BC to the patients and families: 47% of them give information about BC risk during informed consent, and 41% do so at the time of discharge. Notably, 32 surgeons (52%) do not mention the risk of SP, neither at the time of informed consent nor at discharge. Additionally, 35% of the respondents warn local emergency services about the risk of SP in their patients, whereas 65% do not. These results are consistent with the results of 52% of surgeons feeling that the risk of bilateral SP after MIRPE is not significant enough to warrant any action, and 72% of them consider the risk of complications due to BC so exceedingly rare that they do not recommend specific preventive measures. Only 28% of surgeons agree that practical measures should be taken in order to address this risk. Nonetheless, 45% believe that this risk is underestimated.

Discussion

Iatrogenic BC is considered a rare occurrence, even though it was described occasionally following cardiothoracic surgery (1). Specifically, the role of BC as a consequence of MIRPE is poorly understood. As complications related to BC after MIRPE have been very seldom reported as case reports, it is unlikely for individual surgeons to encounter them (4,8-10). While numerous studies and systematic reviews analyze the complications of MIRPE, none have described BC as a reported outcome (3,11).

To better evaluate the implications of BC after MIRPE and its potential life-threatening complications, we conducted a survey within a large population of surgeons performing MIRPE. Main results are presented in Figure 2.

Among the respondents from CWIG, considered experts in PE surgery—they collectively perform more than 1,600 PE surgeries each year—only 45% reported awareness of BC following MIRPE. These surprising findings suggest that awareness of BC as a potential severe complication should be enhanced.

Considering that both PE and SP due to blebs are relatively frequent in pediatric and young adult populations, it seems prudent to search for lung blebs prior to MIRPE (5). Survey results indicate that 35% of respondents do not perform a preoperative CT scan, one-third of the surgeons prefer MRI, and a subset of surgeons do not employ any radiological imaging prior to surgery. High-resolution computed tomography (HRCT) is the most reliable method for studying the lungs and evaluating pulmonary parenchyma, and it should be routinely performed. MRI alone is probably insufficient as the sole imaging modality for lung blebs preoperative assessment. Nonetheless, the search for lung blebs was not widespread among survey respondents, as only 33% routinely used to search for blebs with CT scan prior to MIRPE and 13% during thoracoscopy at the time of surgery. Furthermore, though it seems prudent to treat any detected blebs in patients undergoing MIRPE (with apicectomy and pleurodesis) to mitigate the risk of subsequent SP (potentially bilateral due to BC), a significant portion of CWIG surgeons (47%) disagreed with this precaution, preferring observation in patients with blebs undergoing MIRPE. As the peak incidence of blebs and SP occurs during adolescence, we hypothesize that pediatric surgeons may adopt a more aggressive approach to managing lung blebs than adult thoracic surgeons (12). Since in CWIG the proportion of thoracic surgeons is relevant, this could explain the more conservative approach in bleb diagnosis and management among the respondents.

One of the main objectives of the survey was to investigate the incidence of unilateral or bilateral SP in patients undergoing MIRPE. Our findings indicate unilateral and bilateral SP (not related to residual air in the thorax following thoracoscopy) are relatively frequent (42% and 18%, respectively). These results support the hypothesis that postoperative SP should be considered as a potential cause of respiratory impairment in PE patients, unrelated to surgery. Symptoms in patients with unilateral SP after MIRPE did not differ from typical pneumothorax presentations, principally chest pain and mild dyspnea. As expected, symptoms were more severe in bilateral cases with 23% having severe dyspnea and two cases resulting in cardiac arrest; one death due to bilateral pneumothorax was also reported. We suspect that BC may predispose to the bilateral spread of the pneumothorax originating from a single lung; however, this cannot be demonstrated by our data. An alternative theory is that bilateral pneumothorax developed simultaneously due to a bilateral lung anomaly, but we consider this scenario much less probable.

Two questions of the survey investigated technical surgical factors that could theoretically predispose patients to BC, i.e., the method of mediastinal dissection (large and wide versus narrow tunnel) and the number of bars placed. Most surgeons preferred to place multiple bars, confirming a trend toward the placement of multiple bars that has been observed in the literature in the last years (13). A large and wide mediastinal tunnel that allows an almost complete view of the contralateral thoracic cavity, preferred by 58% of respondents, is a safe option to avoid cardiac injury. Although this approach allows for better visualization of the tip of the dissector during dissection, it could theoretically predispose patients to BC. This could be confirmed by the fact that survey respondents observed bilateral SP more frequently in patients with multiple bars compared to those with single bar.

Effective communication with patients and their families should be a fundamental aspect of clinical practice. Although BC is a rare complication, patients and families should be informed about its risks and the appropriate management strategies if it occurs. Enhancing communication is particularly important if awareness of iatrogenic BC and SP after MIRPE increases among PE surgeons. Accurate information prepares patients for potential, albeit rare, postoperative complications.

The final questions of the survey aimed at evaluating the perception of the surgeon regarding the risk associated with BC. Interestingly, the opinions varied significantly: 48% of the respondents recognized bilateral SP due to BC as a real risk for MIRPE patients, while 46% believed that it is an under-evaluated risk. However, a majority of the surgeons (72%) believe that, due to its extreme rarity, no action should be taken regarding this risk.

A possible limitation is about distinction between postoperative and SP, which is based on cause and presentation rather than timing after surgery. Postoperative pneumothorax typically remains stable, as it results from unevacuated residual air during surgery, whereas SP appears suddenly and tends to worsen due to subpleural blebs. In our survey, two respondents reported a unilateral pneumothorax and three a bilateral one occurring immediately after surgery, without an apparent surgical link. While certainty is not possible, we believe these cases are more likely related to the surgical procedure rather than a SP episode.

Conclusions

The aim of the present survey was not to provide definitive answers about PE surgery and BC, but to contribute to discussing this potentially underestimated issue and to increase awareness of this condition. The following measures could prevent severe consequences of BC after MIRPE:

• To assess lung blebs in the preoperative imaging evaluation (CT or other layered imaging modality);
• To explore lung apex during thoracoscopy;
• To consider the treatment of blebs during MIRPE performing thoracoscopic apicectomy with or without pleurodesis;
• To provide patients’ families with an emergency algorithm and contact telephone numbers in case of need.

We advocate for a multicentric study to obtain evidence-based insights into BC and its clinical implications, in particular, the incidence of bilateral SP, after MIRPE.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SURGE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2287/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2287/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2287/prf

Funding: This work was supported by the Italian Ministry of Health (Ricerca Corrente).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2287/coif). M.M.F. reports Pectus Implant system US and European patent ownership: European Unitary Patent (Issued 26.06.2024), and EP3773279 U-Bloq Chest Wall System-U-Bloq Chest Wall System US Patent (pending). M.M.F. also reports Pampamed SRL Argentina Ownership and Ferroni Medical Corp USA Ownership. The other authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Informed consent was obtained from all individual participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Blacha MMJ, Smesseim I, van der Lee I, et al. The Legend of the Buffalo Chest. Chest 2021;160:2275-82. [Crossref] [PubMed]
2. Nuss D, Kelly RE Jr, Croitoru DP, et al. A 10-year review of a minimally invasive technique for the correction of pectus excavatum. J Pediatr Surg 1998;33:545-52. [Crossref] [PubMed]
3. Hebra A, Kelly RE, Ferro MM, et al. Life-threatening complications and mortality of minimally invasive pectus surgery. J Pediatr Surg 2018;53:728-32. [Crossref] [PubMed]
4. Park HJ, Park CB, Jeong JY. Bilateral tension pneumothoraxes in buffalo chest several months after Nuss procedure for pectus excavatum. J Cardiothorac Surg 2022;17:314. [Crossref] [PubMed]
5. Mendogni P, Vannucci J, Ghisalberti M, et al. Epidemiology and management of primary spontaneous pneumothorax: a systematic review. Interact Cardiovasc Thorac Surg 2020;30:337-45. [Crossref] [PubMed]
6. Huang HK, Chien WC, Chung CH, et al. Pectus Excavatum is Associated with a Higher Incidence of Primary Spontaneous Pneumothorax in a Young Population in Taiwan: A Nationwide Population-based Study. Thorac Med 2019;34:47-57.
7. Huang HK, Huang YJ, Lin KH, et al. Severity of Pectus Excavatum is a Risk Factor for Primary Spontaneous Pneumothorax. World J Surg 2020;44:2035-41. [Crossref] [PubMed]
8. Sakamoto K, Ando K, Noma D. Spontaneous bilateral pneumothorax resulting from iatrogenic buffalo chest after the nuss procedure. Ann Thorac Surg 2014;98:1463-5. [Crossref] [PubMed]
9. Lee J, Jeong JY, Suh JH, et al. Diverse clinical presentation of primary spontaneous pneumothorax in patients with pectus excavatum. Front Surg 2023;10:1245049. [Crossref] [PubMed]
10. Matsuoka S, Miyazawa M, Kashimoto K, et al. A case of simultaneous bilateral spontaneous pneumothorax after the Nuss procedure. Gen Thorac Cardiovasc Surg 2016;64:347-50. [Crossref] [PubMed]
11. Akhtar M, Razick DI, Saeed A, et al. Complications and Outcomes of the Nuss Procedure in Adult Patients: A Systematic Review. Cureus 2023;15:e35204. [Crossref] [PubMed]
12. Huang YH, Chang PY, Wong KS, et al. An Age-Stratified Longitudinal Study of Primary Spontaneous Pneumothorax. J Adolesc Health 2017;61:527-32. [Crossref] [PubMed]
13. Donati F, Cipriani MS, Pistorio A, et al. Pectus Bar Dislocation: Comparison Between Three Different Stabilization Techniques Adopted in a Single Centre. J Pediatr Surg 2024;59:161591. [Crossref] [PubMed]