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| Discussion |
Case Report: A three-year-old child presented with history of recurrent cough and cold since two years and failure to gain weight. Over a period of the past few months, she had often been investigated for recurrent lower respiratory tract infection and failure to thrive. She had been unsuccessfully treated with antibiotics.
Chest radiograph on admission as well as those acquired at various occasions prior to this admission, revealed increased transradiancy of the left lung field with the mediastinum being shifted to the right.(Figs 1 & 2).
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Fig: 1 |
Fig: 2 |
The differential diagnosis of a congenital lobar emphysema and obstructive lesion of the left bronchus was considered and, for further evaluation, a CT scan of the chest was performed. This revealed an anomalous pulmonary vein coursing through the right lung and draining into the infradiaphragmatic vena cava (Figs 3-8).
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Fig: 3 |
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An abnormal branching pattern of the right main bronchus was noticed. An anomalous “upper lobe” bronchus was observed arising form the right main bronchus - being associated with a unilobar right lung. The right main pulmonary artery appeared to be hypoplastic and monosegmental l(Figs 9-12)
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Fig: 9 |
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The anomalous pulmonary vein draining into the infradiaphragmatic IVC can be better appreciated on the sagittal reconstructed image (Fig 13)
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Fig: 13 |
A diagnosis pf Scimitar syndrome was made.
DISCUSSION:
Scimitar syndrome is a rare pulmonary anomaly with abnormal pulmonary venous drainage below the level of diaphragm. It represents a constellation of anomalies that could present variably in any particular case.
The anomalies seen in Scimitar syndrome are:
Various synonyms that have been used for Scimitar syndrome are as follows
The syndrome represents a constellation of above mentioned features – though it is very rare to find all of them in a given patient. Anomalous pulmonary vein and right lung hypoplasia are the most consistent findings.
The word "scimitar" is probably derived from French cimeterre or directly from Italian scimitarra and is appplied to any sword with a curved blade (Fig 14). .
The silhoutte caused by the anomalous pulmonary vein draining into the infrahepatic IVC resembles a Scimitar (sword with a curved blade) , and hence the name.
The respiratory system develops from the ventral wall of the foregut at 3–4 weeks’ gestation. The tracheo-bronchial tree develops between days 24 and 36 of gestation. At 28–30 days, the lung buds continue to elongate, forming the primary bronchi. The right lung grows faster than the left, being both larger and having more generations of bronchial branching. The pulmonary artery develops from the sixth aortic arch and gives off branches that parallel the development of the airways. The common pulmonary vein becomes incorporated into the many pulmonary veins that drain into the left atrium.
As the development and growth of the tracheo-bronchial tree and the pulmonary venous system are parallel, anomalies in the development of one system would adversely affect the other system and would hence, coexist.
Clinical presentations of this syndrome are variable ranging from asymptomatic adults to respiratory distress in a child. Severe pulmonary hypertension and subsequent cardiac failure is a commoner presentation in children than in adults, in whom it is often an incidental finding.
A classic triad that should alert a physician regarding the possibility of Scimitar syndrome includes respiratory distress, right lung hypoplasia and dextroposition of the heart.
Chest radiograph would reveal dextrocardia , scimitar vein and non specific pulmonary disease in the right mid and lower zones. Often, this is because of pulmonary venous congestion secondary to inadequate drainage via the scimitar vein. Clinical suspicion is usually that of infection that fails to clear in spite of adequate antibiotic treatment. This is when, usually a CT scan of the chest is called in for.
CT Chest reveals abnormal pulmonary venous drainage into the infradiaphragmatic IVC/hepatic vein, anomalies of the tracheobronchial tree, and right lung hypoplasia or unilobar right lung and anomalies of the aortic arch.
2D ECHO is indicated to detect the presence of intra and extra cardiac shunts and to quantify the magnitude and directionality of the shunt.
Cine MR with 3D Contrast Enhanced MR angiography are fast becoming the one stop shop in the evaluation of patients in whom the Scimitar syndrome is suspected. Cardiac MRI accurately delineates the anatomical details of the pulmonary arterial as well as venous system, the exact anatomy of the tracheobronchial tree and presence of sequesteration. An added advantage is that of accurate quantification of intracardiac and extra cardiac shunts as well as the presence of pulmonary hypertension that has an important bearing on the further management of the patient.
3D MR angiography may obviate the need for invasive cardiac catheterization in these patients with accurate delineation of the shunts and anomalous vessel anatomy.
There are two indications for surgical intervention:
Surgical treatment is best managed in two steps:
Surgical intervention should be limited to those patients with lung sequestration or recurrent serious chest infections of the affected lung or those with right ventricle overload due to a major left/right shunt. As the syndrome is rare and less number of patients undergo surgical treatment, knowledge regarding the efficacy and complications of the procedure is limited.
Thrombosis or fibrosis of the redirected scimitar vein is a serious complication of the surgical reimplantation procedure, often needing rethoracotomy with resection of the remaining lung .
Prenatal diagnosis of Scimitar syndrome is suspected on fetal 2D ECHO on finding pulmonary venous confluence behind the right atrium and presence of a vertical pulmonary vein.
