Postoperative cavitating infarction following lobectomy: the importance of variant pulmonary anatomy

Abstract

A 75-year-old woman was admitted to hospital with haemoptysis, fever and shortness of breath. She had undergone a right video-assisted thoracoscopic surgery upper lobectomy for an apical lung cancer 4 weeks earlier, and had been treated with antibiotics for 1 week prior to admission for a suspected postoperative lung abscess. Review of preoperative imaging found that she possessed a lobar pulmonary artery variant, with postoperative imaging confirming that the right lower lobe segmental pulmonary artery had been divided alongside the upper lobe vessels. The diagnosis of a lung abscess was thus revised to a cavitating pulmonary infarct. There are numerous variations of the pulmonary vasculature, all of which have the potential to cause a range of serious vascular complications if not appreciated preoperatively. Measures to mitigate the risk of complications resulting from vascular anomalies should be considered by both radiologists and surgeons, with effective lines of communication essential to safe working.

Background

Lung cancer is responsible for the majority of cancer-related deaths worldwide.¹ However, over the last decade, there has been a significant increase in patients with primary lung cancer undergoing lung resection with curative intent, largely secondary to a rise in minimally invasive video-assisted thoracoscopic surgery (VATS).² While VATS procedures are considered safe and effective, a proportion of patients will nonetheless experience postoperative complications.³ This risk is compounded by anatomical variation of the pulmonary vessels,⁴ of which a large number are recognised, often identified incidentally on imaging.^{5 6}

We report a case in which a rare pulmonary artery variant led to a significant postoperative complication in a patient undergoing a VATS lobectomy. This serves to highlight several points, including the need for awareness of surgically significant variant anatomy among both radiologists and clinicians, the importance of careful review of relevant anatomy preoperatively and which approaches may reduce the risk of similar complications occurring in future.⁷

Case presentation

A 75-year-old woman was admitted to hospital complaining of shortness of breath, haemoptysis and fever. This followed a recent elective admission under thoracic surgery just over 1 month prior, during which she had undergone a right VATS upper lobectomy for a T3 N0 M0 squamous cell lung carcinoma. She had been discharged without apparent complication 5 days postoperatively, and routinely reviewed in primary care 2 days later.

One week prior to this emergency admission, the patient had been seen in ambulatory care complaining of severe right scapula pain, and reporting having felt nauseous and intermittently dyspnoeic since discharge. Following a chest radiograph and CT pulmonary angiogram (CTPA), she had been diagnosed with a lung abscess and sent home with oral ciprofloxacin, re-presenting as described when her symptoms worsened.

On examination, she was hypoxic with oxygen saturations of 94% and tachycardic at 94 bpm. Examination of the chest was unremarkable, and all surgical wounds appeared clean.

Investigations

The patient’s initial diagnosis of lung cancer had been made when a right upper lobe (RUL) mass was identified incidentally on a chest radiograph, during a previous admission for a myocardial infarction. Subsequent CT had confirmed the presence of a 2.3 cm right upper lobe nodule (figure 1), which demonstrated marked fluorodeoxyglucose avidity on Positron Emission Tomograpy (PET) CT (figure 2). Mild avidity at the right lung apex was also concerning for a satellite nodule, conferring T3 status. Following lung cancer multidisciplinary review, the patient was listed for curative right upper lobectomy.

Figure 1.

Axial CT image demonstrating a 2.3 cm nodule within the posterior right upper lobe on both lung and mediastinal windows.

Figure 2.

Axial and coronal fluorodeoxyglucose PET-CT images demonstrating an avid right upper lobe lesion.

Three weeks postoperatively, the patient had undergone a CTPA to investigate severe pleuritic chest pain. This had shown a 5 cm gas-filled cavity (figure 3) in the apical segment of the right lower lobe (RLL), and a postoperative lung abscess had been postulated by the general on-call radiologist.

Figure 3.

Post-lobectomy lung-windowed axial and coronal CT images demonstrating a 5 cm cavity in the apical right lower lobe.

A week after treatment with antibiotics, she was admitted with haemoptysis, dyspnoea and fever. Her inflammatory markers were raised (white cell count: 16.6×10⁹/L and C reactive protein: 248 mg/L). She was also mildly anaemic (haemoglobin: 110 g/L).

Chest radiograph on admission showed a doubling in size of the RLL cavity (figure 4). Imaging was reviewed by a cardiothoracic radiologist in the Respiratory-Radiology meeting, where retrospective review of prior cross-sectional imaging revealed that the preoperative staging CT had demonstrated a rare pulmonary artery anatomy variant. The apical RLL pulmonary artery arose from the posterior RUL pulmonary artery, rather than arising from the interlobar pulmonary artery as normal (figure 5).

Figure 4.

Postero-Anterior (PA) chest radiograph showing a large right upper zone cavity.

Figure 5.

Pre-lobectomy axial and coronal CT images showing a common origin for the right posterior upper lobe and right apical lower lobe segmental pulmonary arteries. Red arrows indicate the normal origin of the right posterior segmental upper lobe pulmonary artery from the truncus anterior. Yellow arrows show the ectopic origin of the right lower lobe apical segmental pulmonary artery from the same origin.

Subsequent scrutiny of the postoperative cross-sectional imaging showed that the apical RLL pulmonary artery was no longer discernible, with staple material in the ostial vicinity implying the vessel had been divided alongside the RUL vessels during lobectomy (figure 6). Diagnosis was thus revised to an ‘infected, cavitating infarct’.

Figure 6.

Post-lobectomy coronal and sagittal CT images showing the absence of both the right upper lobe vessels and the right lower lobe segmental pulmonary artery.

Treatment

Due to a previous reaction to co-amoxiclav, the patient had been taking oral ciprofloxacin prior to admission. Given her lack of response to treatment, her case was discussed with microbiology, who advised switching therapy to oral clindamycin. Her inflammatory markers gradually improved on revised antibiotic treatment. Six days after admission, the patient was discharged home with a further 1 month course of clindamycin.

Outcome and follow-up

On review, 4 months after admission, a further chest radiograph demonstrated a significant reduction in the size of the cavity (figure 7), which correlated with markedly improved symptoms. The patient returned to routine postoperative follow-up.

Figure 7.

Postero-Anterior (PA) chest radiograph showing a reduction in the size of the previously demonstrated right lower lobe cavity.

This case serves to highlight a number of issues, including the importance of pulmonary vascular variations, how they may lead to intraoperative error and the vascular complications that may result.

Discussion

Anatomical variation

An estimated 11% of patients undergoing lobectomy demonstrate significant variation in the branching pattern of their segmental pulmonary arteries.⁸ This is most marked within the upper lobes, particularly on the left, where a total of 29 different pulmonary arterial distributions have been described, and the number of pulmonary artery branches supplying the lobe varies from 2 to 7.⁹ The variant described in this case—a common origin of the posterior upper lobe segmental pulmonary artery and apical segmental lower lobe pulmonary artery— is recognised,¹⁰ although the prevalence is debated, with rates varying from 2% to 12%.^{8 9 11}

Although rare, vessel injury accounts for up to 60%–80% of VATS lobectomy intraoperative complications.^12–14 Furthermore, severe vascular complications have been shown to occur predominantly during upper lobectomy,^{12 15} where, as hypothesised, marked variety in the architecture of the upper lobe pulmonary arteries increases the risk of technical error. As such, the presence of variant anatomy may significantly increase the risk of a host of vascular complications, as described below.

Pulmonary infarction

Pulmonary infarction is a rare complication of lobectomy, which may result from vascular injury secondary to perioperative technical issues, or lobar torsion as described below.¹⁶ The probability of iatrogenic injury is compounded by atypical anatomy as described, although both variant vascular and non-vascular structures may influence the risk.¹⁷ Patients typically present with haemoptysis, although the interval between symptom onset is highly variable. Subsequent cavitation and infection may be accompanied by fever, pleuritic chest pain and shortness of breath, as described in our patient.^{16 18 19} While infarction may be treated conservatively with antibiotics, as in this case, it often requires revision surgery for the removal of the affected lobe.^{16 20}

Arterial haemorrhage

The major group of life-threatening vascular complications which occur during VATS lobectomy relate to acute haemorrhage, with thorough appreciation of individual pulmonary artery anatomy essential to minimising risk.²¹ Where massive bleeding does occur intraoperatively, it may necessitate emergency thoracotomy,²² with 0.5%–5.2% of patients undergoing unplanned conversion as a result of bleeding, as well as presenting a significant cause of mortality in its own right.²³ Bleeding occurring postoperatively is more commonly secondary to venous injury, or slippage of a ligature from a major pulmonary vessel.²⁴ As with intraoperative bleeding, resuscitation and further surgical intervention are typically warranted.

Venous haemorrhage

The pulmonary veins vary in number and distribution in up to 30% of patients,¹⁰ with such variation contributing substantially to intraoperative bleeding risk.²⁵ There are multiple reports of inadvertent transection of the pulmonary veins in patients with unusual or complicated variants,^{26 27} leading to life-threatening haemorrhage and/or requiring conversion to open thoracotomy. As with variant arterial anatomy, preoperative evaluation of pulmonary vein anatomy on cross-sectional imaging is essential for surgical planning.²⁸ The basic principles of management are as for arterial haemorrhage.

Lobar torsion

Torsion describes the rotation of a lobe of the lung about the bronchovascular pedicle, leading to ischaemia, and ultimately haemorrhagic infarction.²⁹ This is most commonly seen in the right middle lobe following upper lobectomy. While the impact of abnormal pulmonary artery anatomy on the risk of torsion is unclear, variation in vascular pedicle length is an important risk factor for the development of torsion, with longer pedicles demonstrating increased risk.³⁰ Patients will commonly exhibit fever, tachycardia and shortness of breath.³¹ Diagnosis is best made on contrast-enhanced CT, which demonstrates abrupt tapering of the proximal pulmonary artery and bronchus, alongside loss of normal parenchymal enhancement, ground-glass attenuation and interlobular septal thickening within the affected lobe. Surgical intervention is the mainstay of management.³²

Stump thrombosis

Stump thrombosis is often identified incidentally as a filling defect within the arterial stump on CT; patients may be asymptomatic, but are considered at risk of subsequent central extension, or microembolic disease.³³ Given that the predominant risk factor for stump thrombosis is increasing arterial stump length,³⁴ variations in surgical procedure necessitated by variant anatomy may influence the frequency with which this occurs.

Solutions

Means by which to support careful review of imaging preoperatively should be considered. Preoperative CT checklists have been pioneered in some specialties, such as ear, nose and throat, more than doubling the proportion of relevant anatomical variants identified prior to operative intervention.³⁵ Similar checklists used in review of thoracic imaging might cover the more common pulmonary vessel variants.

Patient workup could also make use of novel imaging techniques as a means of highlighting anatomical variants and vessel branching patterns to the clinico-radiological team.^36–39 Research into the routine use of three-dimensional CT as a tool for detailed preoperative assessment of the pulmonary vasculature prior to lobectomy has demonstrated statistically significant reductions in both intraoperative bleeding and operative time.³⁷ Improving operative safety and accuracy through the assessment of individualised patient anatomy would also be in keeping with the progressive shift towards more personalised medicine.

Effective communication should also be considered essential. Constructive intraoperative communication between members of the theatre team has been shown to reduce error rates⁴⁰ and may help complex anatomical variants to be identified perioperatively. However, effective liaison between subspecialist radiologists and clinicians is equally important, allowing for safe and timely identification of potential issues preoperatively, as well as rapid identification as to the nature and cause of complications postoperatively. Means of facilitating this include clinico-radiological meetings, verbal communication of key findings and ensuring radiologist contactibility.⁴¹

Patient’s perspective.

I knew something wasn’t right shortly after being discharged following the operation; I kept feeling breathless after eating and felt something was wrong. The next fortnight was similar, although I began to feel really unwell about 3 weeks after discharge, developing a severe pain in my right scapula. It got so bad that I had to go to ambulatory A&E, and had a CT scan which I was told showed a lung abscess. I was given antibiotics for this, and sent home, but spent the next few days being very sick. After going into hospital again for an x-ray and blood tests, I was told the inflammation markers in the blood were very high, and I had to go straight to A&E, where I was admitted. The next few days were a very grim time indeed; I felt dreadful, and wasn’t able to eat anything, even after being started on the clindamycin treatment. I have never felt so ill.

I was stable enough to go home about 6 days later, but felt awful. I still have a limited appetite, and find it harder to exercise than before. Having said that, I’m much better than I was, and am now managing to walk for about an hour most days.

Looking back at things, it took some time from the symptoms of the complication arising to getting the right treatment for it, and I wonder whether better cohesion between the teams looking after me would improve things. It seems to me that effective communication is essential for good individualised care, and would help with both diagnosis and treatment of such problems.

Overall, my main feeling is of relief, both at having the tumour removed, and at the fact I’m now recovering. Deciding to undergo the operation in the first place was a really difficult decision, so I do feel grateful that the outcome was positive This experience has obviously affected how I live my life now, and has imposed many restrictions. Understanding what happened and why, however, has meant a great deal to me as I begin to move on with my life.

Learning points.

• A variety of anatomical variations of the pulmonary vasculature exist. Failure to recognise variant anatomy preoperatively may increase the risk of a range of intraoperative and postoperative vascular complications.

• Lung abscess post lobectomy is rare, and infarct should be considered for the evolution of a peripheral cavity postoperatively.

• There are a range of approaches to reducing morbidity and mortality from complications relating to abnormal pulmonary vascular anatomy; effective communication should be considered particularly essential.