Dissection of the pulmonary ligament during upper lobectomy: is it necessary?

Abstract

A best evidence topic was written according to a structured protocol. The question addressed was whether dissection of the pulmonary ligament during an upper lobectomy would result in improved outcomes. A total of 85 articles were found using the reported search, of which eight represented the best evidence to answer the clinical question. The authors, date, journal, study type, population, main outcome measures and results are tabulated. Reported measures were complications associated with dissection (atelectasis, bronchial stenosis, bronchial obstruction and bronchial deformation) and preservation (insufficient lung expansion, pooling of effusion and atelectasis) of the pulmonary ligament, ratio (%) of dead space in longitudinal axis (movement of nonoperated lobes), change in the angle (degrees) of main bronchus on the operated side, overall morbidity and mortality, overall survival and conversion rates. In a randomized control trial, the dissection of the pulmonary ligament revealed no significant difference in the dead space ratio or change in the angle of the main bronchus when compared with preservation. Dissection of the ligament, in theory, reduces the free space in the upper thorax by increasing the mobility of the residual lobes. Dissection of the ligament may lead to bronchial deformation, stenosis, obstruction or lobar torsion. Preservation of the ligament may prevent this complication by suppressing the upward movement of residual lobes. However, this may result in pleural effusion in the free thoracic space that may potentially become infected resulting in an empyema or bronchial fistula. Five large case series were analysed; three routinely dissected the pulmonary ligament and two did not. There was no observed difference in clinical outcomes between the two groups. There is no convincing evidence that dissection of the pulmonary ligament in an upper lobectomy significantly improves outcomes and reduces complications.

INTRODUCTION

A best evidence topic was constructed according to a structured protocol. This protocol is fully described in ICVTS [1].

CLINICAL SCENARIO

A 62-year old man with known squamous cell carcinoma in the right upper lobe, staged T1 N0, underwent an elective right upper lobectomy using video-assisted thoracic surgery (VATS). After careful division of the vascular attachments, you retract the lung anteriorly and superiorly, mobilize and divide the inferior pulmonary ligament. You then contemplate whether omitting this stage of the operation would have affected the patient's peri- and postoperative outcomes.

THREE-PART QUESTION

In (patients undergoing elective upper lobectomy) does (dissection of the pulmonary ligament) result in (improved outcomes)?

SEARCH STRATEGY

Ovid databases Embase from 1974 to December 2012 and Medline from 1948 to December 2012 were used with the following keywords; ‘lobectomy’ OR (‘lobectomy’ [MeSH Terms]) AND ‘pulmonary ligament’ OR (‘pulmonary ligament’ [MeSH Terms]) OR ‘inferior pulmonary ligament’ OR (‘inferior pulmonary ligament’ [MeSH Terms]) OR (‘pulmonary’ AND ‘ligament’). Related articles and references were screened for suitable articles. Google Scholar, Scopus and the Cochrane database were also accessed for similar articles.

SEARCH OUTCOME

Eighty-five articles were found using the reported search strategy. From these, eight articles were identified that provided the best evidence to answer the question. These are presented in Table 1.

Table 1:

Best evidence papers

Author, date, journal and country Study type (level of evidence)	Study group	Outcomes	Key results	Comments
Usada et al. (2010), Surg Today, Japan [2] Survey (level IV evidence)	Questionnaire certified by the Japanese Society of Thoracic Surgery Sent to 102 hospitals for thoracic consultants to complete with 76% responses	Frequency of preservation or dissection of the pulmonary ligament Complications associated with dissecting or preserving the pulmonary ligament	Preservation of the ligament: 69% (n = 54) Regular dissection: 11% (n = 13) Occasional dissection: 17% (n = 9) Half dissection: 3% (n = 2) Most common complications associated with dissection: Bronchial stenosis (n = 21) Atelectasis (n = 8) Bronchial obstruction (n = 4) Most common complications associated with preservation: Pooling of effusion (n = 19) Insufficient expansion of the lung (n = 18) Atelectasis (n = 8)	Preservation of the pulmonary ligament may be useful in preventing bronchial stenosis and obstruction, while its dissection may be useful to prevent the pooling of effusion
Matsuoka et al. (2004), Surg Today, Japan [3] Randomized control study (level Ib evidence)	35 consecutive patients undergoing upper lobectomy for lung carcinomas Two study groups Patients who had inferior pulmonary ligament divided (n = 17) Right upper lobectomy (n = 11) Left upper lobectomy (n = 6) Patients who had inferior pulmonary ligament preserved (n = 18) Right upper lobectomy (n = 12) Left upper lobectomy (n = 6)	Evaluation using CXR (PA) preoperatively and 1-month postoperatively: Ratio (%) of dead space in longitudinal axis (movement of nonoperated lobes) Change in the angle (degrees) of the main bronchus on the operated side	Divided group All 3.5 ± 3.1 Right 3.8 ± 3.5 Left 2.9 ± 2.4 Preserved group All 5.5 ± 6.6 Right 7.9 ± 6.8 Left 0.6 ± 1.4, P > 0.05 Divided group All 49.1 ± 29.1 Right 36.4 ± 26.2 Left 72.5 ± 18.1 Preserved group All 44.2 ± 17.3 Right 36.3 ± 13.8 Left 60.0 ± 12.2, P > 0.05	Division of the pulmonary ligament after upper lobectomy is less effective for the obliteration of dead space than leaving it intact
Narita et al. (1997), Jpn J Soc Bronchol, Japan [4] Case control study (level IIa evidence)	39 patients with division of the pulmonary ligament (18 cases [A1] divided by interrupted sutures and 21 [A2] by autosuture) 16 patients with preservation of the pulmonary ligament	Bronchial deformation Respiratory complaints	Divided group A1: 62.5% (5/8) A2: 100% (8/8) Preserved group Mild bronchial deformation in 20% (1/5) Divided group A1: 11.1% A2: 14.3% Preserved group No complaints	Deformation of the residual bronchus after left or right lobectomy can cause severe stenosis or lung torsion
Congregado et al. (2008), Surg Endosc, Spain [5] Case series (level III evidence)	237 patients underwent major pulmonary resections with dissection of the pulmonary ligament	Conversion Postoperative morbidity Common complications Perioperative mortality	14.01% (n = 22) 15.18% Prolonged air leak (n = 10) Atelectasis (n = 6) Apical air space (n = 6) 3.7%	Performing dissection of the pulmonary ligament during VATS lobectomy may be a viable safe procedure
Walker (1998), Semin Thorac Cardiovasc Surg, UK [6] Case series (level III evidence)	150 patients underwent VATS lobectomy with dissection of the pulmonary ligament	Conversion Postoperative morbidity Common complications 30-day mortality	11.8% (n = 20) 2% Prolonged air leak (n = 17) Bronchopleural fistula (n = 1) 2%	VATS lobectomy with dissection of the pulmonary ligament may be associated with low morbidity and mortality
Daniels et al. (2002), Ann Thorac Surg, USA [7] Case series (level III evidence)	110 consecutive patients underwent VATS lobectomy with dissection of the pulmonary ligament	Conversion Postoperative morbidity Common complications Perioperative mortality	1.8% (n = 2) 19.1% Prolonged air leak (n = 6) Pneumonia (n = 5) 3.6%	VATS lobectomy with dissection of the pulmonary ligament is a safe strategy for patients with early stage lung cancer
Flores et al. (2009), J Thorac Cardiovasc Surg, USA [8] Case series (level III evidence)	398 patients underwent VATS lobectomy and 343 patients underwent thoracotomy. In both cases, pulmonary ligament was preserved	Conversion Morbidity (>grade 3 complications [CTCAE]) Common complications Perioperative mortality	17.6% (n = 70) VATS group (n = 13) Thoracotomy group (n = 3) VATS group: Respiratory (n = 26) Prolonged air leak (n = 17) Thoracotomy group: Respiratory (n = 34) Prolonged air leak (n = 18) One in each group	Survival rates for both procedures are similar, but VATS was associated with fewer complications
McKenna et al. (2006), Ann Thorac Surg, USA [9] Case series (level III evidence)	1100 patients underwent VATS lobectomy with preservation of the pulmonary ligament except during sleeve lobectomies (incidence 0.3%, n = 3)	Conversion Morbidity Common complications Overall mortality	2.5% (n = 28) 15.2% Prolonged air leak (n = 56) Pneumonia (n = 13) Empyema (n = 4) 0.8%	VATS lobectomy with preservation of the pulmonary ligament can be performed with low morbidity and mortality

CXR: chest X-ray; VATS: video-assisted thoracic surgery; CTCAE: common terminology criteria for adverse events; PA: posteroanterior.

RESULTS

Usada et al. [2] conducted a questionnaire-based study that was certified by the Japanese Society of Thoracic Surgery. Current practice in relation to dissection or preservation of the pulmonary ligament was identified, with associated complications, if any, in 102 hospitals. A total of 78 (76%) consultants replied, 54 (69%) hospitals preserved the ligament and 13 (11%) performed regular dissection. Thirty (45%) consultants encountered complications on dissecting the ligament: bronchial stenosis (21 consultants), atelectasis (8), bronchial obstruction (4), pooling of sputum (3) and pneumonia (3). Twenty-six (38%) consultants encountered complications with preservation: pleural effusion (19 consultants), insufficient lung expansion (18), atelectasis (8), empyema (7), pneumonia (7), pooling of sputum (6) and bronchial fistula (5). This study provides level IV evidence and, therefore, is of poor quality.

Matsuoka et al. [3] conducted a randomized control trial of 35 consecutive patients undergoing upper lobectomy for lung carcinomas. This is the only study in this article with level Ib evidence. The pulmonary ligament was divided in; right upper lobectomy (n = 11) and left (n = 6), and preserved in; right upper lobectomy (n = 12) and left (n = 6). There was no significant difference in intra-thoracic dead space ratio between the divided and preserved group. There was no significant difference in change in the angle of the main bronchus in the divided group compared with the preserved group. The angle change tended to be greater after left than right upper lobectomy in both groups.

Narita et al. [4] studied the effect of preservation of the pulmonary ligament on preventing deformation of the residual bronchus in 55 cases. Of these, the pulmonary ligament was excised in 39 cases (Group A) and preserved in 16 (Group B). Group A was further classified into two groups: the bronchial stump was closed with interrupted sutures (A1, 18 cases) or autosuture (A2, 21 cases). Two patients in Group A1 (11.1%) and three in Group A2 (14.3%) complained of respiratory discomfort. There were no complaints in Group B. Deformation of the residual bronchus was detected in 62.5% (5 of 8) of A1 cases and 100% (6 of 6) of A2 cases. Mild bronchial deformation was detected in 20% (1 of 5) of Group B cases. This study is of poor quality as it provides level IIa evidence.

Three large case series [5–7] routinely dissected the pulmonary ligament during upper lobectomy. Conversion rates were 14.01, 11.8 and 1.8%, respectively. Perioperative mortalities were 3.7, 2 and 3.6%, respectively. Postoperative morbidity was higher in the study by Congregado et al. (15.18%) and Daniels et al. (19.1%) compared with the study by Walker (2%). Prolonged air leak was the most common postoperative complication in the above studies. Two large case series [8, 9] published their results of VATS lobectomies with preservation of the pulmonary ligament, except during sleeve lobectomies (incidence 0.3% [n = 3]) [9]. Mortalities were 0.5 and 0.8%, respectively. The conversion rate was higher in the study conducted by Flores et al. (17.6%) compared with McKenna et al. (2.5%). Morbidity was not comparable as Flores et al. used a validated scoring system (Common Terminology Criteria for Adverse Events). However, prolonged air leak arose as the most common complication in both studies. No causal inferences can be made from the results of these case series as they all provide a low level of evidence (level III), and their data, in particular mortality, are not directly comparable due to confounding variables between studies.

CLINICAL BOTTOM LINE

Many thoracic surgeons dissect the pulmonary ligament during upper lobectomy. This, in theory, reduces the free space in the upper thorax by increasing the mobility of the residual lobes. In fact, dissection of the ligament may lead to bronchial deformation, stenosis, obstruction or lobar torsion [10–12]. Preservation of the ligament may prevent this complication by suppressing the upward movement of residual lobes. However, this may result in pleural effusion in the free thoracic space, which may potentially become infected, resulting in an empyema or bronchial fistula. Of the relevant eight articles, only one provided the best available evidence (level Ib) and the remaining were all of generally low quality. Therefore, there is no convincing evidence that dissection of the pulmonary ligament in an upper lobectomy significantly improves outcomes and reduces complications.

Conflict of interest: none declared.