Lung Segmentectomy and Limited Pulmonary Resection

Although lung segmentectomy has always been popular for resection of suppurative lesions and nonmalignant masses, some experts have also recommended it for very early lung cancer.[1, 2, 3] The choice for patients with lung cancer is usually a lobectomy, but in some patients with minimal lung reserve, lung segmentectomy may be an option.[4, 5, 6]

The essence of lung segmentectomy is to remove the lung disease without removing excess normal lung. Because the technique is technically demanding, some surgeons simply prefer to wedge out the lung lesion using a stapler. However, the recurrence rate after a wedge resection remains higher.[7]

With the resurgence of Mycobacterium tuberculosis and development of drug-resistant strains, lung segmentectomy is again becoming a popular technique.[8] Segmentectomy and extended lung resection are also used to treat various fungal infections and congenital lung malformations.

Both lobectomy and pneumonectomy are widely used to treat cancerous lesions of the lung. However, many thoracic patients have chronic obstructive pulmonary disease (COPD) or emphysema and have minimal lung reserve. These patients simply are not able to tolerate extensive lung resections. Segmentectomy is a good option in such patients.

Both segmentectomy and lesser lung resections can be performed via thoracotomy or via video-assisted thoracoscopic surgery (VATS).[9, 10, 11] VATS is fast becoming an option for most patients with thoracic pathology. The technique has been shown to yield better outcomes, less pain, and shorter recovery than traditional techniques.

VATS is currently the criterion standard for both lesser lung resections and segmentectomy. VATS is a better choice than thoracotomy in these settings and is performed with general anesthesia using a camera and a small non-rib-spreading incision. The technique of lesser lung resection and segmentectomy is very similar to the open technique, except that instruments are used to retract and dissect the segmental planes.[9]

Many surgeons remove isolated lung lesions with a wedge resection using VATS.[12] Wedge resection saves time but involves removal of a significant amount of normal lung tissue. Wedge resection is appropriate only for noncancerous lesions or for resecting metastatic lesions. The standard of care for malignant lesions is still lobectomy.[13]

Indications for segmentectomy and lesser lung resections include the following:

• Bronchiectasis
• Early stage I cancer (usually in a patient who has significantly limiting cardiopulmonary disease)
• Lung nodules
• Tuberculosis
• Suppurative lesions

Segmentectomy and lesser lung resections should not be performed in people who have no pulmonary reserve or have numerous comorbidities for a thoracotomy.

Relative contraindications include the following:

• Coagulopathy
• Skin infection over the site
• Diffuse lung disease
• Extensive metastases

Anatomy

When operating on the right side of the chest, the surgeon should be aware that the bronchus is the most posterior hilar structure. The upper-lobe branches of the pulmonary artery are the most superior hilar structures in the chest. When the major fissure is opened, the pulmonary artery can be visible, allowing the surgeon to follow its continuation into the lower lobe.[7]

In the middle lobe, the medial and lateral branches are always opposite one another. In most cases, a posterior segmental artery may arise and supply the posterior segment of the upper lobe.

In the left chest, the pulmonary artery again crosses superiorly above the left mainstem bronchus to become the most posterior hilar structure. The apical posterior, anterior, and segmental branches are readily visible in the anterior and superior direction. As on the right side, a separate posterior segmental artery may be found posteriorly on the main pulmonary artery, either just at or above the major fissure.

In the major fissure, the lingular branches anteriorly and the superior segment branch posteriorly often form a cross on the continuation of the pulmonary artery.

During segmentectomy, it is vital for the surgeon to be aware of the high degree of arterial variability. Each branch must be identified and correctly ligated.

In all cases of segmentectomy, the artery and respective bronchus are divided and ligated. The order of the division depends on which segment is being removed.

When performing segmentectomy of the apical and anterior segment of the right upper lobe, the artery is always ligated first and then gently elevated to locate the segmental bronchus.

For segmentectomy of the posterior right upper lobe, it is sometimes easier to dissect the bronchus first and then ligate the artery. The artery is often deep and not readily visible. Great care must be taken; inadvertent injury can lead to massive bleeding.

On the left side, the pulmonary artery branches to the upper lobe are more easily identified chiefly because the bronchus is the middle structure on that side.

If unsure about the bronchial anatomy, the surgeon may alternatively inflate and deflate the lung on that side to determine the plane of dissection. However, even if a segment is deflated, it may fill via collateral ventilation from accessory bronchi.[7]

After excision of noncancerous lesions with either segmentectomy or wedge resection, most patients do well.[14] However, when these procedures are performed in patients with compromised lung function, the morbidity can be high. In addition to the removal of the lung mass, the thoracic incision and general anesthesia also carry high morbidity in people with no lung reserve. Old data suggest that the overall mortality in healthy people is about 1% but may run as high as 4-6% in individuals with compromised lung function. Even with VATS, more recent mortality figures are in a similar range.[15]

Morbidity and mortality after a segmentectomy are similar to those after a lobectomy. The major complications that increase morbidity include prolonged bronchopleural fistula, empyema, and persistent airspace. All of these are interrelated and may occur in combination. These complications generally arise when the dissection in the intersegmental planes is difficult or there is significant inflammation.

Patients with tuberculosis experience the highest morbidity associated with segmentectomy. As many as 33% of patients with tuberculosis who are candidates for lung resection (lobectomy, wedge resection, or segmentectomy) develop persistent airspace problems, which inevitably result in infection. The resulting pleural cavity empyema is then treated initially with thoracostomy tube drainage and antibiotics.

Morbidity after a lesser lung resection (wedge resection) is minimal. Potential complications include either retention of secretions or pleural problems. Persistent airspace occurs with an incidence of less than 10%.

Segmentectomy is a much less benign procedure than lobectomy or pneumonectomy. Mortality is usually below 1% when the procedure is performed in patients with good pulmonary function. However, in patients with poor lung function and in those who have undergone prior lung surgery, mortality can be as high as 4-6%.[7]

Several large studies have examined wedge resections performed in patients with metastatic lesions.[16] On average, the 5-year survival rate in patents with colon or breast cancer and isolated lung metastases has been about 35%.[17]

Preoperative education of the patient should include techniques of maintaining good bronchial hygiene. The patient must be taught how to generate an effective cough and use the incentive spirometer. Pillows should also be provided to help patients exhale forcefully.

All thoracic surgery procedures carry risks. Preoperative risk identification and amelioration enhance postoperative outcomes. Factors that increase postoperative risk include the following:

• American Society of Anesthesiologists (ASA) class greater than 2
• Advanced age
• Coronary artery disease (CAD)
• Chronic obstructive pulmonary disease (COPD), asthma
• Emergency procedure
• Extensive lung resection
• Immunocompromised individual
• Morbid obesity
• Prolonged surgery
• Extensive bleeding during surgery
• Smoking

If any of the above factors are present, it is important to work up the patient so as to avoid unnecessary complications. Important components of the preoperative workup include the following:

• Thorough history and physical examination
• Pulmonary function test
• Spirometry, blood gas
• Split lung function tests (selectively)
• Cardiopulmonary stress test

Routine pulmonary function tests that must be performed in all thoracic surgery patients include lung volume, lung mechanism, airflow, and gas exchange. Pulmonary function criteria for lung resection include a forced expiratory volume in 1 second (FEV1) of greater than 60%.

Cardiac workup

It is also important to assess the cardiac risk factors in patients undergoing segmentectomy. Thoracic procedures have the highest incidence of associated postoperative congestive heart failure, arrhythmias, and myocardial reinfarction. A thorough cardiac history is vital in the preoperative evaluation of thoracic surgery patients, and the findings should be correlated with appropriate physical finding and results of laboratory testing.

Patients who are completely asymptomatic and have no cardiac risk factors for CAD, regardless of age, usually do not need cardiac testing. Patients with symptomatic heart disease or electrocardiographic (ECG) or laboratory evidence of a cardiac dysfunction suggestive of cardiac disease need further assessment. If symptoms of cardiac disease are present, stress testing should be considered.

Management after segmentectomy or wedge resection is no different from that after lobectomy. Unlike lobectomy, however, segmental and lesser lung resections do not significantly affect lung function.

The decision to initiate or continue mechanical ventilation is usually based on assessment of gas exchange, impending respiratory failure, and the ability to protect the airway. Patients undergoing thoracic surgery usually have an arterial line inserted in the operating room (OR). This allows dynamic blood pressure monitoring and facilitates single-lung ventilation. Arterial blood gas should be frequently sampled to assess both arterial oxygen tension (PaO2) and arterial carbon dioxide tension (PaCO2). Most patients do well with oxygen delivered via facemask or nasal cannula. The thoracic incision does make it painful to take deep breaths; consequently, adequate analgesia is recommended.

Most patients who undergo these procedures can be extubated in the OR. Most patients are transferred to the surgical floor postoperatively, but an overnight stay in the intensive care unit (ICU) is occasionally recommended. To reduce fluid overload, thoracic patients are kept on the dry side. Unless the patient is not eating at all, intravenous (IV) fluids are maintained at a minimum.

Chest tubes are monitored for both air leakage and fluid drainage every 8 hours. Blood work is usually performed once on the following day to assess hemoglobin and renal function. Postoperative chest radiography is routine. Unless the patient has a problem, some surgeons obtain radiographs only before and after removal of a chest tube.[18]

Most patients need good pain control. Today, patient-controlled analgesia (PCA) and epidural catheterization are routinely available in most hospitals and help ease the pain for several days following the procedure. Once the chest tubes are removed, the patient can receive oral narcotics augmented with nonsteroid anti-inflammatory drugs (NSAIDs). If epidural catheters cannot be placed or are contraindicated, pain pumps can be placed in the OR just prior to closure.

Other factors in postoperative care include chest physiotherapy, tracheal suctioning, and ambulation. To prevent atelectasis, incentive spirometry is vital and should be a part of preoperative teaching. The cardiovascular system also has to be closely monitored after surgery. Arrhythmias and myocardial infarction can occur; thus, cardiac monitoring for the first 48 hours is required. The incidence of cardiac complications is higher in elderly patients and in those with preexisting cardiac risk factors.

Most patients remain in the hospital until the chest tubes have been removed and they are able to ambulate and at least tolerate a semisolid diet. Occasionally, in the context of a prolonged air leak, patients are discharged with chest tubes remaining.

Physical therapy is a vital component of postoperative care and should be encouraged.

Prophylaxis of deep vein thrombosis (DVT) is highly encouraged even if patients are ambulatory.

Because most thoracic surgery patients are present or past smokers, oxygen and nebulizer therapy are common.

The average stay after a thoracotomy ranges from 3 to 5 days, but patients who undergo segmentectomy via VATS may be able to go home sooner pending resolution of their air leak. Several series show that VATS allows rapid recovery, is associated with significantly less pain, and reduces postoperative complications.

Irrespective of the type of surgery, most patients need a prescription-strength pain medication for a few weeks at home. Others may benefit from a fentanyl patch.

All patients are seen within 1-2 weeks after discharge. At the first postoperative visit, staples (if placed) may be removed, and a wound check is performed. Chest radiography is performed to assess for full lung expansion, pneumothorax, or pleural effusion. If the procedure was performed for a benign tumor or bronchiectasis, subsequent follow-up is with a pulmonologist. If the mass removed was malignant, continued follow-up with both the surgeon and an oncologist is common.

All patients are encouraged to continue with physical therapy.

Several small studies indicate that thoracoscopic segmentectomy for lung cancer or for congenital and acquired lung disease leads to greater preservation of lung function and exercise capacity as compared with a formal lobectomy. However, there is a need for continued follow-up to ensure that there is no disease recurrence.[19, 20, 21, 22, 23, 24]

Segmentectomy is performed with the patient in the standard lateral decubitus position. Proper padding of the knees, elbows, and dependent axilla is provided.[7]

Various instruments should be used to hold the patient stable in this position, including placement of sandbags under the operating table mattress, rolled sheets in the front and back, and a beanbag.

The dependent arm is flexed at the elbow. If shaving is necessary, only the hair in the incision line should be removed. It is often helpful to outline the proposed incision with a marking pen. Most segmental resections are ideally performed via a fifth interspace incision.

The standard incision usually starts in front of the anterior axillary line and curves about 4 cm under the tip of the scapula. The incision then proceeds vertically between the posterior midline over the vertebral column and the medial edge of the scapula. It is usually unnecessary to go farther than the level of the spine of the scapula. The procedure can also be performed minimally invasively, either with video-assisted thoracoscopic surgery (VATS) or via a robotic approach.

A double-lumen endotracheal tube is preferred.

Once the chest cavity is entered, the lung is collapsed and the entire pleural cavity is examined.

Before the segmentectomy is started, the hilum is identified. All surgeons who perform segmentectomy via VATS or an open approach must be familiar with the anatomy of the bronchus, pulmonary artery, and veins.[25, 26, 27]

With a double-lumen endotracheal tube, it is easy to inflate the entire lung and clamp the bronchus concerned. Once the segment is identified, the rest of the lung can be deflated. The inflated segment will remain filled with air for some time, allowing easier dissection. Once the bronchus has been identified, it can be divided manually or with the use of a mechanical stapler. Unlike with a lobectomy, additional coverage of bronchial closure is usually unnecessary.[7]

Once the artery and bronchus are ligated, traction is applied on the bronchus, and the segment is removed in a retrograde fashion. This plane is developed with gentle blunt dissection, but the pleura is usually divided with scissors. The pulmonary veins come into view as they cross in the intersegmental planes. The segmental veins provide the best view of segmental anatomy. All the individual vein branches are isolated and divided sequentially. This can also be done with a stapler to avoid possible air leakage. (See the image below.)

Apical segmentectomy.

After the lung specimen is removed, the raw surfaces of the lung parenchyma are examined for bleeding. The lung must be expanded gently and assessed for any bleeding or air leakage. If the dissection was done in a segmental fashion, air leakage should be minimal or nonexistent. Minor air leaks often seal within a few minutes after lung expansion.

If an air leak is present, however, it should be addressed. Moderate-sized leaks caused by segmentectomy can persist and lead to infections and residual airspace. If the moderate leak persists, the area may have to be reinforced with a pleural flap or a pulmonary sealant. Suturing the two adjacent lung segments is not recommended, because it may lead to tearing of the lung parenchyma.[28]

Once the lung is expanded, one or two chest tubes should be placed: one in the apex (size 20) and one in the base (size 28). The tubes should be connected to an underwater drainage system, but suction should be avoided until after extubation. Suction with positive-pressure ventilation often leads to an increase in air leaks. Once the patient is breathing spontaneously, the tubes can be connected to suction. At no time should these chest tubes be clamped during transfer of the patient from the operating room (OR) to the recovery room or the intensive care unit (ICU).

Subsequent management of the chest tubes is the same as that for any other lung surgery.

Because of the complexity of performing segmental resection, most surgeons today simply perform a nonanatomic lung resection, better known as wedge resection (see the image below). This technique is widely used to resect lung masses, metastatic lesions, and even localized suppurative infections. Almost any metastatic lesion can be excised by using a wedge resection technique. The technique can also be used to excise multiple lesions from the same lobe or to excise segment(s) from multiple lobes.

Pulmonary wedge resection.

The one negative aspect of performing an anatomic lung resection is that it removes a significant amount of normal lung. This may be of no significance in healthy people, but it may compromise breathing in patients with limited lung reserve.[7]

Limited lung resection may be approached via a standard thoracotomy; sternotomy may be an option in patients with bilateral lung disease. The procedure can also be performed by means of VATS.[29, 16]

Most patients who undergo the procedure via lateral thoracotomy undergo general anesthesia. A double-lumen endotracheal tube is preferred. After the chest cavity is entered, the entire pleural cavity is examined for disease. The lung should be thoroughly palpated to identity any metastatic lesions. Today, the use of staples has made nonanatomic resection very easy.

The lung is grasped along the edges and a stapler is fired. These staplers fire a row of staples while simultaneously transecting the lung tissue. The lesion may be wedged out in a V- or U-shaped incision.

If an electrocautery device is used, a superficial linear incision is first made over the lung with a staple or a clamp. The cautery device is then used to cut out the lung tissue. However, the edges of the lung must be reinforced with a running suture to ensure hemostasis and to avoid air leaks. At higher power, the electrocautery coagulates most small blood vessels. The biggest disadvantage of this approach is that the cautery tip persistently sticks to lung tissues and needs to be scraped constantly.

Postoperative care is the same as that for lobectomy.

Three major complications that can occur during surgery include massive hemorrhage due to injury to the pulmonary artery or its branches, cardiac arrhythmias, and development of a contralateral pneumothorax.

The complications following a segmentectomy and those following a wedge resection are very similar.[30, 31]  The most common complications include the following:

• Air leakage - Most leaks seal within a few days, but large leaks may persist for weeks
• Bleeding can occur at the suture line or if the ligature from the blood vessel has slipped off; thus, it is vital to ensure good hemostasis before leaving the OR
• Residual airspace is uncommon but can occur when a large amount of lung is resected
• Infection of the pleural space can occur when a residual airspace persists; in some cases, the patient may need a muscle flap or an apical tent to close off the residual space and eliminate the infection
• Respiratory failure is not a direct complication of surgery; patients who have borderline lung function are more likely than healthy people to develop respiratory distress in the postoperative period; if the preoperative workup was not adequate or if a high-risk patient underwent surgery, he or she may require prolonged ventilation and even a tracheostomy
• Cardiac complications may include acute myocardial infarction and arrhythmias