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MDCT of Anomalous Unilateral Single Pulmonary Vein

¹ All authors: Department of Diagnostic Imaging, The Ottawa Hospital, Civic Campus, 1053 Carling Ave., Ottawa, ON K1Y 4E9, Canada.

Received November 22, 2003; accepted after revision January 12, 2004.

 
Address correspondence to J. M. Seely (jeseely{at}ottawahospital.on.ca).

Introduction

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We report the imaging findings in a rare case of a unilateral single pulmonary vein identified on chest radiography and contrast-enhanced chest CT. Only a few cases have been reported in the literature describing this interesting rare anomaly that is often confused with arteriovenous malformation and hypogenetic lung syndrome (scimitar syndrome). However, the distinctive imaging features enable the diagnosis to be made and preclude any further intervention.

Case Report

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A 66-year-old woman underwent preoperative chest radiography for open reduction and internal fixation of a displaced ulnar fracture. The chest radiograph (Fig. 1A) showed a tortuous tubular structure originating from the superior aspect of the right hilum. On interrogation, the patient stated she had had previous chest radiographs that were variably diagnosed as scimitar syndrome or "opacity of unknown origin." An arteriovenous malformation was suspected, and 5-mm contrast-enhanced helical CT of the chest was performed. The diagnosis of an arteriovenous malformation was suggested, but because the contrast enhancement was suboptimal, thin-slice MDCT was scheduled to better characterize the lesion. MDCT was performed on a Light-Speed Plus scanner (GE Healthcare) using 2.5-mm slice thickness reconstructed at 1-mm intervals with contrast material (Omnipaque 300 [iohexol], Amersham Health) injection at a rate of 4 mL/sec for maximum opacification of the pulmonary arterial system. An abnormal right superior pulmonary vein draining the right middle and upper lobes was visualized (Fig. 1B). This "wandering" pulmonary vein was seen coursing through the apicoposterior segment of the right upper lobe, extending posteriorly and inferiorly into the right middle lobe, and finally draining into the right inferior pulmonary vein rather than directly into the left atrium (Fig. 1C). No evidence was seen of an abnormal arterial supply to this vessel. The left superior and left inferior pulmonary veins were normal in their course. Hypoplasia of the right middle lobe bronchus was seen, as were accessory fissures in the right middle lobe (Fig. 1D) and the apical segment of the right upper lobe. The bronchial anatomy was otherwise normal, and no other congenital abnormalities were seen. The complex vascular anatomy was better visualized on the volume-rendered images, which clearly showed a wandering vein ultimately draining into the left atrium (Fig. 1E).

View larger version (152K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —66-year-old woman with anomalous unilateral single pulmonary vein. Posteroanterior chest radiography shows tubular tortuous structure originating from superior aspect of right hilum.

View larger version (88K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —66-year-old woman with anomalous unilateral single pulmonary vein. Contrast-enhanced CT scan shows marked enhancement of tubular structure corresponding to abnormal right superior pulmonary vein.

View larger version (96K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —66-year-old woman with anomalous unilateral single pulmonary vein. Anomalous right superior pulmonary vein (solid straight arrow) is seen draining into inferior pulmonary vein (curved arrow), thereby forming a single pulmonary vein (open arrow) before draining into left atrium.

View larger version (140K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D. —66-year-old woman with anomalous unilateral single pulmonary vein. Anomalous right superior pulmonary vein (solid straight arrow) is seen coursing through right middle lobe, which shows accessory fissure (curved arrow). Single right pulmonary vein (open arrow) is also noted.

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1E. —66-year-old woman with anomalous unilateral single pulmonary vein. Volume-rendered image (posterior view) clearly depicts anomalous right superior pulmonary vein (short arrow) joining inferior pulmonary vein (long arrow) before draining into left atrium. Normal vascular anatomy on contralateral side is also visualized.

Discussion

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The pulmonary venous system is subject to various congenital anomalies. The vein may be anomalous in its drainage, its course, or both. In our patient, the right superior pulmonary vein followed an anomalous course but drained normally into the left atrium. This unusual entity was first described by Kozuka and Nosaki [1] as an anomalous unilateral single pulmonary vein. An anomalous unilateral single pulmonary vein is a single vein that enters alone on the ipsilateral side into the left atrium after collecting from all the pulmonary veins. This anomaly may also be associated with hypogenetic lung (seen in our patient) and needs to be distinguished from the hypogenetic lung (scimitar) syndrome. However, the anomalous vein has a normal drainage into the left atrium; hence, no shunt is produced. This anomaly contrasts with the scimitar syndrome, in which the vein crosses the diaphragm and drains into the inferior vena cava.

The other entity that needs to be differentiated from an anomalous unilateral single pulmonary vein is the arteriovenous malformation. However, the absence of any feeding artery supplying an anomalously coursing vascular structure precludes a diagnosis of arteriovenous malformation.

To our knowledge, only a few cases in the literature describe anomalously coursing pulmonary veins [1-5]. Rey et al. [2] summarized 17 cases of an anomalous unilateral single pulmonary vein that most commonly occurred on the right side. Bilateral anomalous single pulmonary veins have also been reported by Hidvegi and Lapin [3], who used 3D reconstructions of helical CT sections for establishing the diagnosis. A closely related entity is the "meandering" vein, which was first described by Goodman et al. [4]. Those authors reported a case of an abnormally coursing vein draining the entire right lung and entering the left side of the left atrium [4]. A meandering vein implies an anomalous course and may or may not represent the sole drainage of the ipsilateral lung. The case described by Goodman et al. was in fact another case of anomalous unilateral single pulmonary vein [3].

Congenital pulmonary venous abnormalities are related to the complex development of the venous system. In the embryo, drainage of the pulmonary venous blood is via the splanchnic plexus into the primordium of the systemic venous system, including the cardinal and the umbilicovitelline veins [6]. Caudal and cranial outpouchings develop from the sinoatrial regions of the heart and extend toward the lung buds, with subsequent regression of the caudal portion [6]. The cranial portion then continues to develop as the common pulmonary vein and by 28-30 days of gestation communicates with the pulmonary venous plexus, which is now being separated from the main splanchnic plexus [6, 7]. By 30-32 days, most connections with the splanchnic plexus are lost and the common pulmonary vein becomes incorporated into the left atrial wall, with the four pulmonary veins separately entering the chamber [7, 8]. Incomplete incorporation of the common pulmonary vein into the left atrium results in a persistent accessory preatrial chamber in the form of a cor triatriatum [8-10]. An anomalous development of the atrial septum or failure of common pulmonary vein to develop can result in a total anomalous pulmonary venous connection [7, 8]. A partial anomalous pulmonary venous connection is due to an incomplete fusion of the common pulmonary vein with the pulmonary venous plexus. As a result, some pulmonary veins retain communication with the cardinal or umbilicovitelline venous system and drain into the right-sided chamber [7-9].

The cause of abnormally coursing pulmonary veins is not well known. Several theories have been proposed. To account for the tortuous course of these veins, it has been postulated that the union of the common pulmonary vein with the pulmonary venous plexus is delayed, which results in pulmonary venous connections with both the umbilicovitelline veins and the left atrium [8, 11]. Obliteration of the splanchnic connection and the persistence of the left atrial connection result in the meandering vein [8, 12].

No treatment is required for anomalous unilateral single pulmonary vein because no vascular shunt is produced [5]. In contrast, hypogenetic lung (scimitar) syndrome and arteriovenous malformation may require surgery [13] or embolization [14] to correct the shunt. It is therefore essential to correctly differentiate an anomalous unilateral single pulmonary vein from these two entities.

In our patient the diagnosis was established with certainty on the contrast-enhanced chest CT scan obtained on an MDCT scanner with volume-rendered reconstructions that show the vascular anatomy in excellent detail. Recognition of this entity is important, and it should be differentiated from scimitar syndrome and arteriovenous malformation, with which it shares some features. Diagnosis of an anomalous unilateral single pulmonary vein precludes the use of invasive diagnostic or therapeutic procedures.

References

Top Introduction Case Report Discussion References

 

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11. Gazzaniga AB, Matloff JM, Harken DE. Anomalous right pulmonary venous drainage into the inferior vena cava and left atrium. J Thorac Cardiovasc Surg1969; 57:251 -254[Medline]
12. Morgan JB, Forker AD. Syndrome of hypoplasia of the right lung and dextroposition of the heart: scimitar sign with normal pulmonary venous drainage. Circulation1971; 43:27 -30[Abstract/Free Full Text]
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This Article Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Agarwal, P. P. Articles by Matzinger, F. R. Search for Related Content PubMed PubMed Citation Articles by Agarwal, P. P. Articles by Matzinger, F. R. Social Bookmarking                      What's this?