Master Techniques in Surgery: Thoracic Surgery: Lung Resections, Bronchoplasty, 1st Ed.

11. Open Middle Lobectomy

Gunda Leschber

 INDICATIONS/CONTRAINDICATIONS

Indications

Middle lobectomy is indicated for pathologic changes involving the middle lobe. This includes mainly malignancies of the lung like primary lung cancer or lung metastases from extrapulmonary tumors. Bronchiectasis, middle lobe syndrome, and bullous changes of the middle lobe or large hamartochondroma are benign changes that justify middle lobe resection. Removal of the middle lobe is the least common resection of all pulmonary lobes. Only approximately 6% of lung cancer originates from the middle lobe.

Complete resection of the middle lobe with additional systematic lymphadenectomy is the treatment of choice for lung cancer limited to segment 4 and 5. However, in the presence of central tumor growth or tumor invasion of the upper vein, upper bilobectomy becomes necessary. Mostly, the middle lobe vein originates from the upper vein; therefore, separation of these two veins is often difficult or even impossible when attempting R0 resection in malignant disease.

Sometimes tumors in the upper or the lower lobe invade the interlobium thereby infiltrating the middle lobe. In these cases an upper or lower bilobectomy (upper or lower lobe as well as the middle lobe) is indicated. The same holds true in case of infiltration of the interlobar artery in lower lobe tumors or lesions at the origin of the lower lobe bronchus, because the middle lobe bronchus is often located just opposite of the bronchus of segment 6 (apical segment of lower lobe).

Neoadjuvant therapy may decrease the size of a tumor which then can be removed as middle lobectomy instead of more extensive resection. Neoadjuvant therapy is also indicated in case of operable patients if lymph node involvement is proven (N2 disease).

Besides surgical management of middle lobe malignancies, radio- or chemotherapy are nowadays accepted alternative treatment strategies in evidence-based medicine.

Placement of stents in an occluding tumor is rarely indicated as the middle lobe bronchus is very small and difficult to be stented.

The so-called “middle lobe syndrome” is a problem of recurrent infection of the middle lobe resulting in local lymph node swelling (around the middle lobe bronchus) that leads to further occlusion of the middle lobe and subsequent retention of secretions. The aetiology of the middle lobe syndrome could be infectious disease (i.e., granulomatous, tuberculosis) but often it remains unclear; sometimes a long and small middle lobe bronchus may be the cause of this syndrome.

Contraindications

As the middle lobe is the smallest lobe, resection seldom results in severely impaired lung function. However, because the risk of pneumonectomy is relevant (see Complications), an alternative treatment to surgery should be chosen if the patient is potentially inoperable in view of lung function or general condition.

 PREOPERATIVE PLANNING

In case of pulmonary nodules, suspicious for malignancy (size, margins, radiologic pattern, growth), an attempt should be made to achieve histology prior to surgery.

Bronchoscopy with transbronchial biopsies is the least invasive procedure to gain samples for histologic examination. Furthermore, the investigation discloses endobronchial tumor growth and defines resection margins. Extensive resections like sleeve resections or bilobectomy are indicated in cases of endobronchial tumor growth in the intermediate bronchus.

In addition, bronchoscopy offers the option to achieve microbiologic specimen, especially if infection is part of the tumor problem or if the lesion is thought to be rather of infectious than malignant origin. Accordingly, antibiotic treatment and inhalation therapy should be initiated and hence the patient’s condition optimized for surgery.

If bronchoscopy does not reveal the etiology of the lesion, CT-guided needle biopsy is recommended.

Prior to surgery examination of the functional status, that is, lung function tests, diffusion capacity testing, blood gas analysis, ECG, etc. according to guidelines should be performed.

Nowadays all patients have CT scans prior to surgery; this should be done with contrast agent to allow separation of pulmonary vessels from lymph nodes on CT scans. In case of malignancy most patients will receive FDG-PET/CT as well.

It is important that the surgeon studies the CT scan and is familiar with the specific anatomy of the patient prior to surgery.

Positioning

Middle lobectomy can be performed as open (thoracotomy) or as thoracoscopic procedure (video-assisted thoracoscopic surgery [VATS]). For anterolateral thoracotomy, the patient is placed in the lateral position with the operated side upward and the table slightly turned backward. The arms are positioned in forward elevation. The surgeon stands anteriorly and the assistant posteriorly to the patient. For posterolateral thoracotomy, the patient is slightly turned forward exposing scapula and spine. The surgeon stands posteriorly and the assistant anteriorly to the patient. In VATS we prefer the anterior approach as the intercostal spaces are wider in the anterior than in the posterior part and less musculature overlaps the ribs. Both, surgeon and assistant, stand anteriorly with the video monitor placed opposite of them. The patient is intubated which allows single-lung ventilation of the nonoperated side.

The patient is secured to the operative table with one safety strap over the hips and pads posteriorly at the lower spine and the upper thoracic spine and anteriorly to the pubic bone. The upper part of the body is stabilized anteriorly by placing the arms on well-padded boards in forward position. From the spine to the sternum the whole thorax is prepped with a chlorhexidine–alcohol solution including also the axilla and upper part of the upper arm.

 SURGERY

Technique

The following description will be detailed for the open approach but it is basically true for the thoracoscopic approach as well. When performing the procedure by VATS one should have a low threshold to convert to the open technique in cases of impaired visualization or complications. Because the vessels to the middle lobe come from the interlobar artery and drain into the upper pulmonary vein respectively, insufficient visualization may lead to accidental transection or disrupture of vessels of the upper or lower lobe. This would result in additional lobectomy, in the worst case even in right-sided pneumonectomy.

We prefer anterolateral approach for thoracotomy as all important structures are located ventrally. The incision is carried out through the subcutaneous tissue and the musculature of the thoracic wall (M. serratus ant.) is spread. The latissimus dorsi muscle as well as the pectoralis major muscle is kept intact. Along the upper rim of the fourth or fifth rib the intercostal muscles are divided until the thoracic cavity is entered. A self-retaining retractor is inserted. Inspection for adhesions (often encountered in patients with bronchiectasis) or any intrapleural pathology is performed and the lobes are explored. The major fissure often is well developed allowing separation of the lower and middle lobe whereas the minor fissure (between the upper and middle lobe) shows broad parenchymal bridging in many cases. Inspection also includes the lymph node stations before it can be determined whether pathology is resectable.

Hilar Dissection

Dissection starts at the anterior hilum by incision of the mediastinal pleura. To do so, the lung is pushed dorsally and held in this position either with a sponge stick or a parenchymal clamp (i.e., Duval lung forceps). This maneuvre exposes the anterior hilum with the vessels, fatty tissue, lymph nodes (station 10), and phrenic nerve. Care has to be taken to prevent harm to the phrenic nerve which lies close to the hilar vessels and may be buried in fatty tissue. There are always small vessels accompanying the nerve longitudinally which are better visible than the nerve itself (Fig. 11.1). The pleura overlying the pulmonary vessels is grasped with DeBakey forceps and incised perpendicular to the axis of the vein with electrocautery or Metzenbaum scissors (Fig. 11.2). Preparation of vessels is performed until the vessel wall is bare. The upper pulmonary vein is the first vessel encountered as it partially overlaps the mainstem of the pulmonary artery (Fig. 11.3).

Figure 11.1 Situs with anterior hilum: Mediastinal pleura overlying the vascular structures. Phrenic nerve, vena cava, and azygos vein clearly visible.

Figure 11.2 Grasping of the mediastinal pleura for incision. Upper lobe is pushed dorsally.

Dissection of Veins

Dissection is started at the upper pulmonary vein with exposure of the branches to the middle lobe and those to the upper lobe. A small sponge stick is used for blunt dissection of surrounding tissue from the vessel wall. Mobilization of the different veins is facilitated by pushing toward the lung parenchyma. The branching of the pulmonary vein becomes visible, allowing identification of the parts to the middle and upper lobe (Fig. 11.4). Once the middle lobe veins are clearly identified, a right-angle clamp is passed behind the vessel and a suture or small vessel loop (1 mm) may be placed to lift the vein up for better dissection of its posterior wall. Directly behind the vein, the interlobar artery is located. Care has to be taken to stay away from the underlying interlobar pulmonary artery which sometimes sends early branches to the middle lobe that may be harmed if the clamp is passed too forcefully. The wall of the artery usually presents as a more yellow structure behind the vein which appears more bluish because of its thinner vessel wall.

Figure 11.3 Mediastinal pleura incised exposing partially dissected upper pulmonary vein and arteries to middle and lower lobe as well as lymph nodes.

Figure 11.4 Exposure of venous branches to middle and upper lobe.

The middle lobe veins are closed either by using a vascular stapler or a ligature and transfixation ligature (Figs. 11.5 and 11.6). For the ligature we prefer resorbable suture material (i.e., Vicryl) and for the transfixation ligature monofilar material (i.e., PDS) but it can also be done by silk or nonresorbable material (i.e., Prolene). For small venous vessels a single 2.0 or 3.0 ligature is sufficient. A further alternative especially in VATS procedures may be the closure with self-locking vascular clips (i.e., Hemolock or PDS clips). In general it is sufficient to place a metal clip at the peripheral side which will then be removed with the specimen.

Figure 11.5 Closure of middle lobe vein by suture ligation and clip application.

Figure 11.6 Passing of an Overhold clamp behind the second middle lobe vein.

Dissection of Arteries

Once the middle lobe veins are separated, the proximal branch of the middle lobe artery is encountered as a vessel originating medially from the interlobar artery within the interlobium (Fig. 11.7). As additional safety measure we tend to encircle the central pulmonary artery with a vessel loop at the beginning of the operation. In case of bleeding the main pulmonary artery can safely be occluded by tightening the vessel loop allowing less stressful closure of any vascular bleeding.

Figure 11.7 Dissection of middle lobe artery.

Figure 11.8 Dissection of major fissure.

However, as there are mostly more than one middle lobe arteries, complete visualization of all arterial branches is recommended. Therefore, the middle lobe is now placed anteriorly exposing the major fissure.

Dissection in the interlobium (Fig. 11.8) will lead to the interlobar part of the pulmonary artery which is usually found at the confluence of the major and minor fissures. The visceral pleura is held up with a DeBakey forceps and incised by electrocautery or Metzenbaum scissors. In this area there is rarely a complete bridging of lung parenchyma, so dissection can be carried down to the artery which presents itself again as a yellowish structure. Here, lymph nodes of station 11 are lying on top of the interlobar artery and as soon as they are lifted up the wall of the vessel becomes visible.

Resection of lymph nodes in the interlobium is often necessary before the artery and the whole vascular situation is clearly understood. Once the visible wall of the interlobar artery is completely freed from surrounding tissue, further dissection upward (centrally) with the scissors or bluntly with the small sponge stick will identify further lymph nodes next to the branches of the middle lobe arteries. Lymph nodes are again gently grasped at their capsule and dissected from the arterial wall. Removal of the lymphatic tissue off the arterial branches is performed over a distance of 0.6 to 1 cm to allow easy and safe closure of the vessel. It also enables the vessel to stretch if further manipulation is performed at the level of the interlobar artery. This might be necessary if there are two separate arteries to the middle lobe when only the distal branch may be encountered from the interlobium.

Once all arterial branches are identified and dissected, a right-angle clamp is passed behind each middle lobe artery and closure and transsection is started. Again, either stapling devices, clips or ligatures and transfixation ligatures are used in analogy to the venous closure.

In case of benign disease the order of vein and artery separation can be changed.

Dissection of Bronchus

Removal of the lymph nodes in the interlobium (station 11) also gives a better exposure of the middle lobe bronchus which lies posteriorly to the middle lobe artery (Fig. 11.9). The bronchus originates from the intermediate bronchus just opposite of the bronchus to the apical segment of the lower lobe (B6). Once the middle lobe artery is transected, the bronchus is clearly visible. It is a rather small structure with the typical cartilaginous impression when palpating. By pulling the middle lobe anteriorly, the bronchus can be identified by placing it between the thumb and index finger. In general the external diameter is not larger than 6 to 7 mm.

Figure 11.9 Exposure of middle lobe bronchus and middle lobe artery which run parallel.

While dissecting along the wall of the bronchus one will encounter bronchial arteries which have a diameter of less than 0.5 mm but a strong arterial wall as they belong to the high pressure system. They are grasped and coagulated before being transected. However, one has to be careful using diathermy in the proximity of the wall of the bronchus because thermic lesions in the bronchial wall will impair healing and can cause insufficiency of the bronchial closure.

Once the bronchus is completely freed from the surrounding tissue, an Overhold clamp can encircle it (Fig. 11.10) and a stapler is passed. The bronchus should be transected close to its origin from the intermediate bronchus. Due to the small diameter of the middle lobe bronchus a medium-size stapler is usually sufficient.

Alternatively, open transsection of the bronchus can be performed with hand sewn closure of the stump. For this maneuvre, the bronchus is held upward with a surgical forceps and dissected with scissors 1 mm off its origin (Fig. 11.11). The advantage of open resection is direct inspection of the resection margin for residual disease, which can also be confirmed by frozen section. If necessary, bleeding from bronchial arteries is punctually coagulated.

For closure of the bronchus we use interrupted stitches with resorbable monofilar suture (PDS, 4.0 or 3.0), alternatively nonresorbable sutures can be used. We close the bronchus with three to four stitches, but running suture may also be an option. The bronchial wall is stabilized by holding it with a surgical forceps when the sutures are placed. One should grasp the bronchial wall only exteriorly as the mucosa and endothelium are very vulnerable to manipulation. The sensitive bronchial mucosa can easily be harmed, especially if bruised by blunt forceps like DeBakey. Surgical forceps in contrast have a pin that indents the mucosa just at one place. This is of advantage if the complete bronchial wall needs to be grasped with the placement of one branch of the forceps on the inside and the other on the outside. Sutures are placed 0.5 mm from the resection line. The first suture is placed at the junction of the membranous to the cartilaginous part of the bronchial wall bringing the cartilaginous parts together. The end of the suture is secured with a hemostat and held without tension allowing the bronchus to stay open while the following stitches are placed 1 mm apart from one another. The next stitches are placed anteriorly (toward the surgeon) again in the cartilaginous wall and only the last stitch is the one that approximates the membranous part of the bronchial wall. Once all sutures are laid, the assistant pulls up on the hemostat which approximates the bronchial wall and facilitates placement of the knots by the surgeon. No force is needed while tying the knots as the bronchial wall approximates well and normal postoperative swelling will further increase tightness of the sutures. Too much tension on the other hand buries the risk of necrosis of the bronchial wall.

Figure 11.10 Passing of an Overhold clamp behind the middle lobe bronchus.

Figure 11.11 By pulling the middle lobe bronchus upward, transsection of it close to its origin from the intermediate bronchus is facilitated.

Figure 11.12 Placement of stapler to transect minor fissure.

After closing the bronchus, patency proof is performed by underwater inspection of the bronchial stump while the anesthesia reinflates the lung. Inflation of the lung also allows to distinguish the level at which the parenchyma has to be transected if the minor fissure is not well developed. The inflated part of the upper lobe is clearly differentiated from the noninflated parenchyma of the middle lobe. The use of a stapler (80-mm stapler or even two cartridges of medium-length staples) is generally recommended (Figs. 11.1211.14). If, in contrast, the minor fissure is well developed, division of it can be performed by using electrocautery, bipolar current or Ultrascision/Harmonic scalpel. No alteration of the parenchyma of the upper lobe will result in a well-developed fissure, so there is no need for additional parenchymal closing. The same holds true for the division in the major fissure between middle and lower lobe. Here often well-defined fissure will allow separation of the parenchyma without the need of a stapling device. An alternative to stapling devices is clamping of the parenchyma of the remaining lobe and transecting it above the clamp. The parenchyma will then be closed with a running suture (i.e., Vicryl) underneath the clamp going back- and forward. The suture is tied on both ends; the clamp removed and the visceral pleura closed with another absorbable suture by approximation of the visceral pleura above the first suture line.

Figure 11.13 Minor fissure divided.

Figure 11.14 Situs after removal of middle lobe.

There is no need for placing stay sutures to hold the remaining lobes in place, as insufflation will result in complete expansion of the upper and lower lobe, closing the place of the former middle lobe completely.

One thoracic drain placed dorsoapically with its tip located in the apex is generally sufficient. However, a second drain may be placed further caudally if felt necessary by the surgeon.

 POSTOPERATIVE MANAGEMENT

Patients undergoing middle lobe resections will be observed postoperatively in an ICU or IMC because of the thoracic drain(s) in situ. As soon as they are awake oral intake is permitted starting with water or tea and proceeding to a light meal at the evening of the operation. Patients should be mobilized out of bed early on and intensive respiratory exercise including coughing, deep breathing, and inhalation is also started on the day of surgery to prevent atelectasis or pneumonia. The use of an incentive spirometer needs instruction of the patient and should be done throughout the whole postoperative course.

A chest x-ray is taken in the ICU to observe expansion of the remaining lung and the placement of the chest tube. There is no need for prospective administration of antibiotics unless clinical evidence of infection.

Postoperative bronchoscopy is rarely indicated; however, if secretion retention due to poor coughing develops one should perform a bronchial lavage to prevent atelectasis or pneumonia.

Adequate pain management is essential in the postoperative course. Particularly in open lobectomies (thoracotomy) displacement of ribs in the costovertebral and costosternal joints by the self-retaining rib spreader can cause long-standing pain. Sufficient pain medication in the early postoperative phase by epidural catheter or patient-controlled analgesia (PCA) can prevent the development of a postthoracotomy syndrome. Not only thoracotomy but also patients undergoing VATS procedures need adequate pain medication as alteration of intercostal nerves can be produced by either procedure itself or by the chest tube which irritates the parietal pleura.

The thoracic drain is observed for air leak and secretion and can be removed as soon as no air leak is observed for >8 hours. Here, the usage of a digital pump device is beneficial as it shows the air leak in a diagram over time. There is a discussion about the maximum amount of drainage which indicates the time of removal: In Europe 200 mL/24 h are commonly accepted, up to 400 mL/24 h in the United States. A chest x-ray in two dimensions is suggested in the postoperative period prior to drain removal and an additional one the day after the drain removal.

Postoperative subcutaneous injection of heparin is started and continued throughout the hospital stay to minimize the risk of venous thrombosis and pulmonary embolism.

 COMPLICATIONS

Complications following middle lobe resection are rare, more common are problems during the procedure itself.

Concerning the anatomy of the middle lobe, there are some characteristics which are important to know by any thoracic surgeon. The arteries to the middle lobe originate from the interlobar part of the pulmonary artery, mostly as two separate arteries (A4 and A5). The arteries are encountered when dissecting the interlobium caudally to the branching of the anterior pulmonary truncus (A1–3) but prior to the origin of the ascending A2. Sometimes there are variations in the form of just one middle lobe artery or a middle lobe artery originating more distally in the interlobium. In rare cases one branch of the middle lobe artery comes off the artery to the anterobasal segment (A8).

Especially in chronic infectious situation enlarged or even calcified lymph nodes may be strongly adherent to the segmental arteries. To avoid massive bleeding, proximal control of the right main pulmonary artery is advisable at the beginning of the operation.

The venous drainage of the middle lobe in general goes into the upper pulmonary vein either as two separate veins or one larger vein with distal branching. However, there is a wide anatomical variety of smaller veins draining into branches of the upper lobe veins, especially into the V2.

The range of anatomical variations includes venous drainage into the lower pulmonary vein or even the combination of one middle lobe vein draining into the upper and one draining into the lower pulmonary vein. Complete exposure of the middle lobe veins is warranted as occlusion of venous drainage from other lobes may lead to hemorrhagic infarction of the involved segments.

The bronchus of the middle lobe originates from the ventral side of the intermediate bronchus. It may be just opposite of the upper segmental bronchus of the lower lobe (B6) or sometimes even almost distal to the branching of B6.

The challenge of middle lobe resection lies in the specificity of having one part of the resection close to the upper lobe (the vein) and the other close to the lower lobe (the artery and bronchus). Accidental confusion of the anatomy may result in an unforeseen pneumonectomy.

The rate of exploratory thoracotomy is higher in middle lobe tumors than tumors of other locations—this is also due to the anatomic relations.

Postoperative complications are the same as in all other lobectomies: Infections, retention of secretion, arrhythmia, and so on. There is hardly a risk of torsion of the remaining lobes; in general the space of the former middle lobe is immediately filled by the expanding upper and lower lobe. This is also the reason why disrupture of the bronchial stump closure is virtually unknown.

 RESULTS

It is difficult to find reports on results of middle lobe resection as the number of cases is relatively low: Only 6.4% to 7.3% of all lung cancers have their origin in the middle lobe and survival rates are not generally split into type of lobe resection. However, Rivera et al. (2014) reported that in right-sided lung tumors prognosis did not depend on the type of lobar resection (middle lobe) but on pTNM status when compared to other right-side lobes. Over time (1980 to 2009) they noted a decrease in the rate of pneumonectomy or exploratory thoracotomy for middle lobe cancers.

 CONCLUSION

Middle lobe resection is the least often lobar resection performed because tumors rarely arise in this lobe and other diseases are uncommon as well. As the middle lobe has anatomic peculiarities with the venous drainage shared with the upper lobe and the arterial and bronchial structures in close relation to the lower lobe, the key element to successful resection lies in perfect knowledge and exposure of the anatomy. Otherwise, the risk of unintended bilobectomy or even pneumonectomy is high. Postoperative complications are rare especially bronchial stump insufficiency.

Tumor patients are treated according to their stage and followed regularly.

Recommended References and Readings

Edward M, Kent EM, Blades B. The anatomic approach to pulmonary resection. Ann Surg. 1942;116:782–794.

Gudbjartsson T, Gudmundsson G. Middle lobe syndrome: A review of clinicopathological features, diagnosis and treatment. Respiration. 2012;84:80–86.

Miura H, Kato H, Konaka C, et al. Primary lung cancer of the middle lobe. Is its prognosis poor? Lung Cancer. 1996;14:273–279.

Peleg H, Antkowiak JG, Lane WW, et al. Prognosis after resection of non-small cell lung cancer of the right middle lobe. J Surg Oncol. 1987;35:230–234.

Riquet M, Hidden G, Debesse B. Direct lymphatic drainage of lung segments to the mediastinal nodes. An anatomic study on 260 adults. J Thorac Cardiovasc Surg. 1989;97:623–632.

Rivera C, Mordant P, Pricopi C, et al. Is the rate of pneumonectomy higher in right middle lobe lung cancer than in other right-sided locations? Ann Thorac Surg. 2014;97:402–407.

Sakao Y, Okumura S, Mingyon M, et al. The impact of superior mediastinal lymph node metastases on prognosis in non-small cell lung cancer located in the right middle lobe. J Thorac Oncol. 2011;6:494–499.



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