Feasibility investigation of uniportal video-assisted thoracoscopic anatomical lung resection for pulmonary sequestration

Pulmonary sequestration (PS) is a rare congenital malformation of the lung, in which an island of the lung parenchyma lacks a normal communication with the tracheobronchial tree and receives arterial blood supply from an aberrant branch of systemic circulation rather than the pulmonary circulation, whereas the venous connection is almost normal via pulmonary veins or systemic circulation [1]. As one of the most common types of a congenital abnormality of the lower respiratory tract, PS accounted for 0.15–6.4% of all congenital pulmonary malformations [2]. The theory of the embryologic basis of PS is still unclear, and one of the most widely accepted explanation is that PS results from the formation of an accessory lung bud caudal to the normal lung bud [3, 4]. Generally, the anomalous arterial blood supply usually comes from single or less multiple branches of the thoracic aorta, followed by the abdominal aorta and intercostal artery [5]. According to the presence or absence of independent visceral pleura covering at the normal lung parenchyma, PS can be divided into two types: intralobar and extralobar pulmonary sequestration [6]. Intralobar pulmonary sequestration (ILS) is often found in the lower lobes, especially in the left lower lobe. However, extralobar pulmonary sequestration (ELS) can appear in many spaces, common in the lower lungs and the spine, occasionally in mediastinum, diaphragm, abdomen. PS can often cause respiratory infection, which will lead to a mass of complications, from common pneumonia, emphysema, and lung abscesses to severe hemoptysis, congestive heart failure, and even malignant transformation [4, 6, 7]. Therefore, this means that it is very important to diagnose the PS correctly. Digital subtraction angiography (DSA) once considered being the gold standard for the diagnosis of PS, because it clearly shows the aberrant vessels. So far, with the advent of non-invasive techniques, such as computed tomography angiography (CTA) has become the most commonly used clinical practice in the diagnosis of PS, DSA has fallen out of favor, because of its ingenuity.

Currently, surgical resection is the best way to treat PS regardless of symptoms, to resolve lesions, make a definite diagnosis and prevent future complications [8]. Previously, many surgeons have demonstrated the feasibility of thoracotomy in treating ILS and ELS [6, 9]. With the development of VATS surgical techniques and sophisticated instruments, VATS has increasingly become the preferred operative procedure in the treatment of PS, which is associated with the potential advantages including less postoperative pain, better cosmetic results, and faster recovery [10‐14]. The pursuit for mini-invasive keeps promoting the evolution of VATS from traditional multiple-port to single-port for most VATS resections, and with the progress of VATS experience, UVATS has become technically feasible to perform lung resections. When compared with traditional multiple-port VATS, UVATS was found to result in equivalent perioperative outcomes and reduced postoperative pain and discomfort [15]. Despite these advancements and the popularization of the UVATS technique, lung resection for PS remains a prohibited area. The technical restrictions come from both dense pleural adhesions and the unknown abnormal arteries. Therefore, UVATS in the treatment of PS had seldom been reported [16‐19]. Nevertheless, as far as we know, this is the largest number of patients that report the use of UVATS in the treatment for PS.

Herein, the present study aimed to share some points for dealing with the abnormal arteries and discussing the safety and feasibility of lung resection by UVATS for patients with PS.

All the surgeries were carried out using the UAVTS approach successfully with no intraoperative conversions or complications. Also, no aberrant artery ruptured or massive hemorrhage occurred.

21(87.5%) ILS were received lobectomy and 3(12.5%) ELS were received mass excision. Overall mean surgery time was 102 mins (range, 55–150 min), the mean blood loss was 94 ml (range, 10-300 ml), the mean days of chest tube maintained were 4 days (range,1-10 days), and the mean postoperative hospitalization days was 6 days (range,2-11 days) (Table 3). No patients died during the perioperative period and only one patient developed early postoperative complications: asymptomatic pneumothorax. (Table 4).

All patients were diagnosed as PS according to postoperative pathology and were cured, without cough, fever, hemoptysis, and so on, occurring during the average follow-up of 17 months (range, 3-35 months). (Table 3).

PS is an uncommon lung tissue that lacks communication with the normal bronchial tree and receives its aberrant artery blood supply from the systemic circulation, most frequently the descending aorta [1]. PS is classified into two main types: ILS and ELS. ILS is the most common variant, accounting for 75–93% of all PS cases [6, 21, 22] and 87.5% in our study. Both two types are more common in lower lobes in the literature [6], and all patients in our study located in lower lobes, especially in the left lower lobe. PS is a congenital and benign disease, but the potential complications are serious, which may include common pneumonia, emphysema, lung abscess, severe hemoptysis, congestive heart failure, and even malignant transformation [23‐25]. Therefore, surgical resection of PS is the preferred and definitive treatment of choice after the diagnosis is made.

The conventional surgical procedure is open posterolateral thoracotomy, which is safe and feasible, however, this technique might lead to greater trauma and pain, and patients recover more slowly [3, 26]. More recently many surgeons have confirmed the feasibility of VATS for PS, because of its minimally invasive, pain relief and quick recovery [10‐14]. However, surgeons’ pursuit of ultimate minimally invasive goals never stops. At present, UVATS has become an increasingly popular approach for surgical treatment of thoracic diseases, including PS. The potential advantages of UVATS include more intuitive vision, less postoperative pain, reduced paresthesia, and better cosmetic results compared with the conventional multiple-port VATS [27, 28].

Nevertheless, UVATS remains many difficulties, as they still some controversies regarding the safety and feasibility associated with this technique, including small operating space, instruments interfering with each other and fewer entry points for introducing staplers [15]. In addition to the PS patients, repeated infections lead to dense adhesion of the pleural cavity, and more importantly, the aberrant arteries are very concealed and difficult to handle. All of the aforementioned challenges may be the contraindications of the uniportal access for the resection of PS.

In our institute, we have quite a lot of UVATS experience, in addition to conventional lobectomy and segmentectomy, and many complex operations, such as bronchus sleeve lobectomy, double sleeve lobectomy, and trachea resection can be performed, which have overcome some limitations of the UVATS itself. However, to our knowledge, only few previous studies of UVATS in the treatment of PS were published [16‐19, 29]. The first challenging step is to separate the presence of extensive adhesions. The following is to make the identification and closure of the aberrant artery, which is a supply from the systemic circulation. In case of failure to safely remove aberrant arteries, it can lead to fatal catastrophic hemorrhage. In this case, it is necessary and relatively safe to follow the principle of “first abnormal blood vessels, posterior pulmonary blood vessels”, priority to closure aberrant arteries.

In this study, anatomical lung resections of PS were carried out using the UAVTS approach successfully with no significant postoperative complications and no perioperative death in all 24 cases. In terms of skills and details during operation, the following conclusions are made: (i) Preoperative preparations must be sufficient, as for patients with symptoms of infection, antibiotics must be used to control the symptoms of infection, because repeated infections not only suggest that patients may have extensive pleural adhesions, but patients in the infected period are prone to postoperative sepsis, it also increases the difficulty of identifying aberrant arteries. In addition, preoperative CTA, if necessary combined with MRI or DSA, to identify the caliber and number of aberrant arteries, is essential for surgical planning. As the principle of “first abnormal blood vessels, posterior pulmonary blood vessels” is followed, it is an indispensable rule to get the basic information of the aberrant artery before surgery. (ii) The importance of a single incision is not negligible, an approximately 3 cm single incision is made in the fifth intercostal space along the anterior axillary line and slightly backward. Because the PS is basically in the lower lung, and the aberrant arteries are usually located in the inferior pulmonary ligament, and the incision is slightly backward to gain better exposure of the aberrant arteries, which can make the vision more intuitive and increase the safety of the operation. (iii) For most patients with PS, pleural adhesions are present, and 16 of our 24 patients had various kinds of adhesions. For pleural adhesions, we should carefully and alternately use the gauze with oval forceps and electrocoagulation hook, as little as possible lung injury and extensive oozing, less lung air leakage, and postoperative drainage, fully loosening adhesions, mainly increase lung freeness, easy to flip, adjust the angle, get a better surgical vision. Of course, thoracotomy or multiple-port VATS is a wise choice when the adhesions are too dense for dissection by UVATS. (iv) Before any lung resection is performed, the most important step is to find out the aberrant arteries. Combined with the preoperative images and clinical experience, the aberrant artery is mainly located in the inferior pulmonary ligament and enters the lung tissue. Note that some uncommon local sources, such as abdominal aorta and intercostal artery, and so on, in this study, most of the aberrant arteries could be identified by preoperative CTA and other tests, without damage to aberrant arteries, the mean intraoperative blood loss was 94 ml (range, 10-300 ml) and the most bleeding patient was 300 ml, mainly due to dense adhesion of the pleural cavity. (v) Drawing on our experience, removal of the aberrant arteries should depend on their caliber and avoid blind clamping, cutting and sewing. The smaller aberrant artery was first ligated proximally using a non-absorbable suture, then proximally and distally clipped with hemo-o-Lock clips, and then finally was cut with scissors. However, the bigger aberrant artery was also first ligated proximally using a non-absorbable suture and then divided using a vascular endostapler. Due to the local infection, lacking of muscle layers and high pressure of aberrant artery, it is easy to rupture and hemorrhage, so suture ligation is very necessary to reduce the risk of bleeding. Following make sure that all aberrant arteries are processed. Sometimes more than one aberrant artery may exist, if there are any omissions, and the pulmonary veins are divided first, it will cause the congestion of the lungs to occupy most of the chest, which will interfere with the surgical field and increase the risk of surgery. In addition, if the aberrant artery branch left unprocessed, it may encounter unpredictable damage that causes the aberrant arteries to retract to the mediastinum or inside the diaphragm causing uncontrollable bleeding. We strongly recommend that for a wider inferior pulmonary ligament, careful dissection must be done to ensure that the isolated aberrant arteries are not missing. Besides the number of aberrant arteries determined should be consistent with the preoperative images, and any suspect aberrant artery should be treated with caution. In our studies, one patient was found to have rapid hyperemia and swelling of the diseased lung after the inferior pulmonary vein was cutting off. Almost half of the chest cavity was occupied, and the anesthesiologist found that there was also oozing in the double-lumen endotracheal. After careful investigation, a small diameter of about 8 mm was presented in the lower part of the inferior pulmonary vein originated from the descending aorta. After the dissection of this aberrant artery, hyperemia and swelling of the diseased lung and oozing in the double-lumen endotracheal were stopped. (vi) For ILS patients, although literature reported that sublobar resection was feasible, we recommend lobectomy to reduce the likelihood of recurrence. We have previously reported the UVATS lobectomy procedure [20]. For ELS patients; only need a mass excision, but because the anatomical location is close to the esophagus, surgery should be careful to avoid injury to the esophagus, if necessary, a stomach tube can be applied to assist operation preoperative or intraoperative. (vii) Last but not least, in the surgical operation surface, especially on the stump of the aberrant arteries, the fibrin glue is covered to reduce the air leakage, exudation and drainage, so that the chest tube can be removed early and the hospital stay can be shortened.

Additionally, the potential limitations of the present study may include a small size of retrospective cases study, and a lack of statistical data analysis with other surgical approaches. In our further study, we would increase the sample size and further investigate the clinical outcomes to confirm the safety and feasibility of UVATS technique for anatomical lung resection of pulmonary sequestration.

In virtue of the surgical technical advantages, anatomical lung resection for PS patients using the UVATS approach ensured the safety and feasibility of the procedure and might benefit more patients with PS from minimally invasive treatment. Moreover, UVATS approach might be associated with less postoperative pain, reduced paresthesia, and better cosmetic results compared with the conventional thoracotomy or multiple-port VATS approach.