Lung torsion is the rotation of a lung or lung lobe about its bronchovascular pedicle and resulting in ischemia. It is very rare and typically occurs in the setting of lobectomy or pneumonectomy. It has also been reported as a rare complication of less invasive procedures such as video-assisted thoracic surgery (VATS) 11, following large-volume thoracentesis 15, or even spontaneously in the native lung.
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Epidemiology
It has a reported incidence of 0.09-0.4% 12.
Pathology
Torsion results from rotation of a lobe (or entire lung) around hilar structures. The degree of rotation is variable, ranging from 90° to 360° (most commonly 180°).
The torsed lung creates a trifold compromise of the airways, arterial blood supply and the venous-lymphatic drainage 13 due to luminal kinking. The affected lobe often shows hemorrhagic infarction or necrosis.
Risk factors
Described predisposing factors include 7 :
- presence of a pneumothorax and/or pleural effusion
- existence of a free and long vascular pedicle to the lung
- existence of a non-ventilated lobe
Location
In the setting of a prior lobectomy this has been classically described affecting the middle lobe where there has been a right upper lobe resection 18.
Radiographic features
Plain radiograph
On plain film, it can be suspected when a collapsed/consolidated lobe is seen in an unusual position especially in the context of a recent pneumonectomy 4. The affected lobe is often opacified 5. Rapid opacification of the lung following trauma/surgery or marked change in position of the opacified lobe on short interval serial radiographs or an unusual position of a collapsed lobe can aid to the diagnosis. Other radiographic findings include inappropriate hilar displacement and a reticular pattern from venous congestion.
CT
Findings are often non-specific and the involved lung may simply appear atelectatic. A high index of suspicion, particularly in the post-surgical setting, is required. CT angiography, especially with maximum intensity projection (MIP) reconstruction, is particularly useful in demonstrating a twisted pulmonary artery morphology 16.
- bronchovascular findings
- tapered obliteration of the proximal pulmonary artery and accompanying bronchus (may appear similar to mucus plugging 16)
- antler sign: abnormal curved orientation of the main pulmonary artery with branch vessels appearing to originate from a single side (versus normally-distributed arborisation) 16
- amorphous soft-tissue attenuation at the hilum
- pulmonary parenchymal findings
- loss of normal parenchymal enhancement
- poorly-enhancing consolidation with increased volume
- ground-glass attenuation
- interlobular septal thickening
- intralobular linear attenuation
- abnormal appearance of the fissure
- post-lobectomy "neofissure" can appear to bulge, with unusual orientation
- change or unexpected position of lobectomy surgical staples may also provide evidence for abnormal rotation 17
Treatment and prognosis
Lung torsion is considered a medical emergency. The optimal therapeutic approach remains controversial 14. The decision for detorsion or lobectomy usually depends on the viability of the torsed lung which is better appreciated after open thoracotomy. Detorsion offers lung salvage but if inappropriate, it may lead to thoracotomy and lobectomy.
Differential diagnosis
Other early or late post lobectomy complications (pneumonia, vascular occlusion) with similar clinical presentation.
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