Introduction

Pulmonary sequestration (PS) is a rare congenital lung anomaly defined as an area of lung tissue with an anomalous systemic blood supply and various forms of venous drainage. This lung tissue does not communicate with the tracheobronchial tree and has histologically abnormal bronchial epithelium. PS most commonly present as recurrent pneumonia [1]. Thirty per cent of pulmonary sequestration is incidental findings [2]. The gold standard of treatment for PS is surgical resection via thoracotomy or video-assisted thoracic surgery (VATS) [3]. The technique of visualizing the demarcation line using indocyanine green contrast dye (ICG) during pulmonary resection has recently been developed, and it has a relatively high success rate.

Case Presentation

Patient 1

A 44-year-old male patient was admitted to our hospital due to cough and recurrent episodes of pneumonia during the last 2 years. CECT chest showed multiloculated cystic solid and low-density mass in the right lower lung (Fig. 1A, B). The area of the lesion received its blood supply from anomalous systemic artery originating from coeliac trunk (Fig. 1C). Muscle-sparing moderate anterolateral thoracotomy was performed. Intraoperatively, the boundary of the sequestration was not clear. The aberrant arterial supply was identified and ligated distally. Intraoperative, indocyanine green was injected into the atypical vessel (10 ml ICG (2.5 mg ICG)), and pulmonary sequestration turned green. A sequential atypical lung resection could be completely removed with parenchyma preservation (Fig. 3C, D). Postoperative course was uneventful, and the patient was discharged on postoperative day 8. Pathological findings of the resected specimen showed inflammatory lung tissue, with multiple cystic spaces willed with purulent secretions.

Fig. 1
figure 1

A, B Chest CT showing a section of pulmonary sequestration and the systemic feeder artery (white arrow), C feeding vessel coursed from the coeliac trunk directly into the cystic solid mass (white arrow)

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Patient 2

The second patient was a 53-year-old lady presenting with chest pain, cough and expectoration for 2 years not responding to general management and antibiotics. The patient had a history of smoking and pulmonal emphysema. CECT showed a low-density mass in the right lower lung lobe, with a feeding arterial vessel arising from the abdominal aorta (Fig. 2). As in the first case, atypical wedge resection was performed via a muscle-sparing anterolateral right thoracotomy. This was diagnosed as PS and resected using per-operative indocyanine green with parenchymal preservation and ligation of feeding vessel (Fig. 3). A sequential atypical lung resection could be completely removed with parenchyma preservation. The postoperative course was uneventful, and the patient was discharged on postoperative day 9. The postoperative chest radiograph demonstrates well-expanded lungs with interlobar effusion (Fig. 4C, D). Pathogenic analysis revealed an aberrant artery, a dilated bronchus, bronchitis and alveolitis with multiple cystic spaces. One-year after surgery, she is going well.

Fig. 2
figure 2

A–C Computed tomography of a 53-year-old female patient diagnosed with pulmonary sequestration and with the systemic feeder artery (white arrow). D, E An aberrant arterial supply arising from the abdominal aorta is indicated (white arrow)

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Fig. 3
figure 3

A, B Intraoperative findings of aberrant artery (white arrow). Distal clamping of aberrant vessel (black arrow). C, D Intraoperative visualization of pulmonary sequestration after injection of ICG into the aberrant artery

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Fig. 4
figure 4

A, B Preoperative chest radiograph with pulmonary multiloculated cystic solid and low-density mass in the right lower lobe. C, D Postoperative chest radiograph demonstrates well-expanded lungs with interlobar effusion (patient 2)

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Discussion

This report shows in two cases of intralobar PS the safety and utility of ICG-guided pulmonary resection for intralobar pulmonary sequestration. PS is a very rare anomaly and accounts for 0.15 to 6.4% of all congenital lung malformations [4]. In most cases, PS has a single feeding artery; among the total blood supplied, 70% originates from the thoracic aorta and (6.9–31.6%) from abdominal aorta [5]. For the therapy of PS, there are various options such as surgical resection of PS combined with percutaneous endovascular embolization of the feeding systemic vessel. The gold standard of PS involves surgical resection especially for symptomatic patients, while asymptomatic patients are often treated with surgery to avoid infection, massive haemoptysis and damage to the lung parenchyma. In our cases, thoracoscopic surgery was not possible in adulthood because of severe adhesions after recurrent pneumonia and recurrent pleuritis. Sublobar resection is usually performed for small sequestration. Traditionally, the boundaries were identified intraoperatively with inflation/deflation of the target segment by clamping and unclamping the relevant bronchus.

Intraoperatively, the extent and delineation of PS was not clear, so ICG was used as part of an open-surgical procedure. A parenchyma-saving wedge resection was performed after thoracotomy and visualization of PS by injection of ICG into the aberrant vessel. PS could be visualized 3–8 min after injection. In contrast to methylene blue, ICG has been used as a contrast agent for intraoperative detection of PS because of its hepatic clearance and its limited systemic side effects [6]. Only few cases of pulmonary resection for intralobar pulmonary sequestration using ICG have been reported. In most cases, ICG is given intravenously and repeatedly [7,8,9]. In our cases, the ICG was injected directly into the aberrant artery. However, the incidence of anaphylactic shock due to ICG used for angiography at doses of 25 to 75 mg was reported to be 0.05%. Although the dose of ICG was quite low at 3 mg in the present cases, the demarcation line of target segment was clearly identified, so this dose of ICG was sufficient for identification of the segmental line. Using such a low dose of ICG is safe, as well, by helping avoid anaphylactic shock.

Conclusions

The intraoperative use of Indocyanine green can greatly facilitate the presentation of the extent of a lung sequestration and safe resection.