|Year : 2008 | Volume
| Issue : 3 | Page : 121-123
Diverticulum of kommerell: Role of imaging revisited
Venkatraman Bhat, Mariam Al Kuwari
Department of Radiology, Hamad Medical Corporation, Doha, Qatar
|Date of Web Publication||17-Jun-2010|
Department of Radiology, Hamad Medical Corporation, Doha
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bhat V, Al Kuwari M. Diverticulum of kommerell: Role of imaging revisited. Heart Views 2008;9:121-3
| Introduction|| |
A case of kommerell's diverticulum arising from the origin of left subclavian artery in association with right aortic arch and demonstrated by dynamic MRA is presented.
Diagnosis of vascular impression was initially suspected by a contrast esophagogram, subsequently confirmed by Gadolinium enhanced dynamic angiography. Modern imaging methods play key role in the investigation of suspected vascular impressions. Algorithms for the workup of suspected vascular impression with or without respiratory symptoms are different in view of need for demonstration of airway anatomy in patients with signs of airway compression. Magnetic resonance angiography (MRA) is traditionally considered as preferred modality for vascular anatomy  . However multidetector computed tomography (MDCT) has its own merits in assessing airways in addition to the vascular anatomy. Comparative roles of computed tomography versus magnetic resonance angiography are presented in this article. Importance of 3D surface rendering of imaging data in the evaluation of vascular structures as well as airways is emphasized.
| Case Presentation|| |
A five-month-old male patient was investigated for attacks of choking. Clinical examination was unremarkable. Radiography of the chest revealed hyperinflated lung fields. [Figure 1] A. No clear impression can be made regarding the position of the aortic arch. Visceral situs was normal. For exclusion of gastro-esophageal reflux (GER), the patient underwent barium esophagography. Extrinsic, predominantly posterior indentation was demonstrated [Figure 1] B in the upper esophagus on esophagogram, leading to suspicion of a vascular anomaly.
Patient underwent Gadolinium (Gd) enhanced dynamic Magnetic resonance angiography for demonstration of suspected vascular anomaly. Contrast enhanced MRA demonstrated presence of right aortic arch with aberrant left subclavian artery. The origin of the aberrant vessel was aneurysmal indicating a Kommerell's diverticulum [Figure 2] A. Focal area of relative luminal narrowing was shown just beyond the diverticulum. 3D surface rendered display optimally demonstrated the vascular anatomy as well as the short segment of narrowing [Figure 2] B.
Patient was recommended for MDCT evaluation but did not turn up for the study.
| Discussion|| |
Diverticulum of Kommerell represents a dilated vascular structure from the remnants of the 4th aortic arch, at the origin of the subclavian arteries. Burckhard Friedrich Kommerell first described it in 1936 in his scholarly description of the aortic diverticulum, which bears his name. In the international literature, however, the name of Kommerell survives only as an eponym.
The diverticulum often arises from the origins of aberrant subclavian arteries. Large diverticulum may lead to signs of esophageal, bronchial or pulmonary arterial compression. Multidetector computed tomography or Magnetic resonance angiography are the studies of choice for demonstration of this anomaly. Many authors consider magnetic resonance angiography as a first choice, however the role of these imaging modalities needs to be reviewed in the light of recent advances in MDCT imaging. Indication for the study of anomaly may be prospective when investigating cases of suspected esophageal vascular impression or at times for best possible assessment of associations when diagnosis is already made with another study.
Diverticulum of Kommerell is a relatively rare vascular anomaly of the aortic arch ,, . Kommerell in 1936 reported an aberrant right subclavian artery originating from the descending thoracic aorta of a left-sided arch in association with persistence of a remnant of the right dorsal aorta. Diverticulum of Kommerell may either arise from the left arch with right aberrant subclavian or from the right aortic arch with the left aberrant subclavian artery. When the aortic arch is right sided there are more complex associations like fibrous band, tracheal compression, etc , .
Compression of the trachea can occur with both right aortic arch - aberrant left subclavian artery and with left aortic arch-aberrant right subclavian artery. However, the patterns of compression are different. With a right arch-aberrant left subclavian artery, compression may be at the level of the aortic arch and/or aberrant subclavian artery, often associated with a Kommerell's diverticulum. Compression of the distal airway with a midline descending aorta may also be present additionally  . Donnelly et al. found compression of the distal airway (carina or main bronchi) remote in location from the arch and Kommerell's diverticulum. This distal compression cannot be explained by the presence of a tight ring at the level of the arch and subclavian artery or Kommerell's diverticulum alone. These patients all had an associated abnormal midline position of the descending aorta  . Such associations need careful scrutiny since it may constitute indication for surgery. Keeping these factors in mind, imaging methods should maximize the yield for demonstrating all associations. Although common teaching that left aortic arch with an aberrant right subclavian artery is not associated with symptomatic airway compression, there are patients of airway symptoms in this category, who on cross sectional imaging had compression of the trachea at the level of the arch and aberrant subclavian artery  .
Computed Tomographic angiography (CTA) and MR imaging methods are equally employed in demonstration of these anomalies  . Magnetic resonance imaging has traditionally been the imaging modality of choice in evaluating these patients  . Advantages of the technique include not utilizing radiation and use of small volume of non-iodinated contrast. Distinctive limitations are the need for longer sedation, limited availability and poor assessment of the airway. However, with the recent advances in helical CT with faster image acquisition, CT imaging is increasingly taking a larger role in the evaluation of these patients  . Both CT and MR imaging have been reportedly useful in describing the anatomy associated with right aortic arch and aberrant left subclavian artery. When to use MDCT as against MRA depends upon whether or not patient has airway related complaints. In equivocal cases, MDCT may be preferred as additional information about the pulmonary pathology which may be valuable in patient's management. Multi-detector CT has the advantage of rapid imaging which reduces the need for sedation in patients with compromised airways  . Our patient was investigated with MRA alone. MDCT examination definitely would have added valuable pulmonary or airway related information.
Complicating factors in the management of the patients are size, location of the aneurysm, additional aneurysm in the adjacent aorta, association of additional fibrous bands or cardio-vascular anomalies, stenosis of the distal artery and location and extent of airway compression. Vascular stenosis of the subclavian artery as noted in our patient has not been previously reported in the English literature. The exact incidence of the total spectrum of anomaly may become more evident with larger database and routine usage of non-invasive modalities in all clinically suspected cases.
With newer CT units with faster image acquisition and lower radiation dose, there is much better display of airway anatomy. 3D rendered image of the airway is most optimal for displaying airway anatomy. Also, superimposition of angiographic data over the airways shows precisely the nature of compression. Even those remote compressions over the distal trachea by the distal aorta are easily identifiable. With all these added advantages, CTA techniques may be preferred over MR despite the inevitable radiation dose.
| Conclusion|| |
In view of complex associations with this condition, altering management options, relative merits of current non-invasive imaging methods, namely CTA and MRA, in achieving maximum yield are discussed. MDCT examination is recommended as a first choice in patients with respiratory symptoms.
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[Figure 1], [Figure 2]