Case Based Pediatrics For Medical Students and Residents
Department of Pediatrics, University of Hawaii John A. Burns School of Medicine
Chapter VIII.8. Pulmonary Vascular Anomalies
Jason H. Brown and Edward W. Fong, MD
March 2003

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This is a 5 year old female who presents to the clinic with shortness of breath, a cough with "lots of mucus" for the last two days, and fever as high as 39.0 degrees C two days ago to 37.0 degrees C this morning. Her parents are worried that she has been getting many chest colds with fevers for the last year and that she coughs and feels out of breath even when she isn't sick. Dextromethorphan cough syrups have not helped her symptoms. Exertion makes her cough worse. There are no other associated symptoms including muscle weakness, cyanosis, hemoptysis, chest pain or dizziness. Her past medical history shows no major illnesses or hospitalizations. Her growth and development have been good. Her family history is not contributory. Review of systems is non-contributory.

Exam: VS T 37.0, HR 85, RR 40, BP 110/68, oxygen saturation 97% in room air. Height and weight are at the 25th percentile. She is a pleasant, comfortable, alert, well-developed, well-nourished 5 year old who is non-toxic and in no acute distress. HEENT and neck exams are normal with no lymphadenopathy. Her cardiac exam is abnormal with the PMI 3 cm right of the midline of the sternum, a palpable sternal lift, a widely split S2, and a grade 2/6 systolic ejection murmur heard greatest over the pulmonic area. Some jugular venous distention is also present. Her respiratory exam shows moderate tachypnea with normal chest percussion and symmetrical chest movements. Some fine crackles are heard throughout the lung bases bilaterally. Her abdomen is soft and non-tender, but notable for hepatomegaly with the inferior liver margin extending 4 cm below the right costal margin. Her back is non-tender. Her extremities show normal muscle bulk, tone and strength, with normal DTRs and peripheral pulses.

A CXR shows dextrocardia, cardiomegaly, right lung hypoplasia, a dilated right main pulmonary artery, increased right pulmonary vascular markings, and right-sided pulmonary infiltrates versus atelectasis. A large vein in the right hemithorax raises the possibility of scimitar syndrome. An EKG shows right axis deviation (presumably due to dextrocardia), but is otherwise normal. An echocardiogram shows a dilated right atrium and right ventricle consistent with volume overload and 2 aberrant veins draining 70% of the pulmonary venous return into the vena cava instead of the left atrium. A large 1.5 cm artery off the aorta is present, feeding into the right lower lobe. No ASD (atrial septal defect) is found. CT scans confirm the findings of the echocardiogram. A cardiac catheterization is performed to determine the pressure in the left atrium, which is found to be elevated.

She is diagnosed with pneumonia and scimitar syndrome consisting of 2 anomalous pulmonary veins draining into the vena cava and a large systemic artery 1.5 cm in diameter originating from the aorta perfusing part of the lung. In addition, pulmonary pressure is elevated and with signs of right heart failure (including JVD and hepatomegaly) due to the increased pressure within the pulmonary system. Her pneumonia is treated with antibiotics.

Upon resolution of the pneumonia 2 weeks later, her pulmonary hypertension and CHF are determined to be improved enough for her to undergo surgical correction. The shunt and feeding artery are removed without complications and over time, her symptoms of CHF and pulmonary hypertension resolve.

Scimitar Syndrome (Partial Anomalous Pulmonary Venous Return):

Normal pulmonary venous circulation carries oxygenated blood from the alveolar capillaries to the left side of the heart for systemic distribution. In the Scimitar syndrome (approximately 1-3 per 100,000 births), an anomalous vein connects between the pulmonary venous circulation and systemic venous circulation which creates a left-to-right shunt that is determined by: 1) size and number of abnormal draining veins, 2) the source of venous blood flow (i.e., veins from the inferior lobe in an upright individual drains more blood than those of the superior lobe), 3) the level of pulmonary vascular resistance, and 4) the presence of other cardiovascular abnormalities. This anomalous pulmonary venous return can be either partial (PAPVR) or total (TAPVR), each with respective clinical presentations. The syndrome associated with PAPVR has been given many names in the past: pulmonary venolobar syndrome, pulmonary vascular syndrome, hypogenetic lung syndrome, and right pulmonary artery syndrome, but it is now more commonly known as "Scimitar syndrome" (1), due to the resemblance of the abnormal curvilinear pulmonary vein to a Turkish sword.

The anomalous venous connections and associated malformations are almost exclusively right-sided, with only a few reports of left-sided occurrence. The syndrome is composed of findings of: 1) An anomalous right pulmonary venous connection to the systemic venous circulation either above or below the diaphragm, most commonly to the inferior vena cava. This vein is what produces the characteristic "scimitar" shadow on X-ray. 2) Anomalous systemic arterial supply to the right lower lobe from the aorta. 3) Hypoplastic (or absent) right pulmonary artery. 4) Right lung hypoplasia with dextrocardia (the dextrocardia is typically the non-situs inversus type, and therefore, is usually a consequence of the right sided pulmonary hypoplasia). Other findings may include: a) Abnormal lobulation of the lung, b) Horseshoe lung, and c) Accessory hemidiaphragm.

Approximately 25% of presenting patients have an associated cardiac malformation, most often an ostium secundum defect (a type of ASD). Racial, sexual, and genetic predilections are largely unknown. PAPVR, was a diagnosis made at autopsy until the advent of echocardiography, cardiac catheterization, and CT/MRI scanning. The abnormal drainage of blood in the lungs can overload the right atrium and ventricle as well as decrease the preload for the left ventricle. This can lead to right ventricular dilation and decreased cardiac output. Additionally, flow from the perfusing artery stemming from the aorta may be greater than the outflow from anomalous veins, leading to increased left-sided volume loading, accelerated pulmonary hypertension, and associated symptoms of cardiac failure (2). This is not normally the case, as most symptoms arise from increased volume loading of the right heart (due to increased venous return) and pulmonary artery pressure is generally normal (3). The most common early clinical manifestation is an increased frequency of pulmonary infections.

Manifestation of clinical symptoms is dependent on the size of the shunt magnitude, expressed as pulmonary flow (Qp) to systemic flow (Qs), and can become serious when this ratio becomes >2:1. Clinical symptoms mainly manifest late in life, depending on the shunt magnitude, but occasionally they may present in childhood. These include: 1) symptoms of recurrent respiratory infections, 2) dyspnea, 3) exercise intolerance, 4) palpitations, 5) hemoptysis, 6) chest pain, 7) symptoms of associated abnormalities (e.g., ASD, pulmonary sequestration, etc.). Symptoms 2 through 6 are rare except in advanced cases where pulmonary hypertension and heart failure are present.

Physical exam reveals symptoms similar to an atrial septal defect:

1. A precordial bulge, which is a left parasternal lift due to right ventricular dilation, and possible pulsation in the 2nd intercostal space due to pulmonary artery dilation (in the absence of dextrocardia).

2. Systolic ejection murmur heard over the pulmonic area.

3. Widely split heart sound (S2) with possible normal respiratory variation.

4. This is usually a non-cyanotic condition unless there is the presence of ASD with pulmonary hypertension for shunt reversal.

5. Right-sided heart failure (include jugular venous distension, hepatomegaly, and peripheral edema).

The differential diagnosis includes: 1) atrial septal defect (clinical picture is almost indistinguishable), 2) total anomalous pulmonary venous return, 3) pulmonary sequestration, 4) ventricular septal defect.

The diagnosis of scimitar syndrome rests on demonstration of the aberrant pulmonary veins and associated abnormalities. Chest X-ray, ultrasound (echocardiography), and MRI are the choice imaging modalities for this purpose, with cardiac catheterization providing additional information in many cases. Treatment of PAPVR is symptomatic for resultant CHF, but the most definitive treatment for prevention of further complications is surgical correction of the shunt. A contraindication for surgical repair is the presence of pulmonary hypertension, which can increase the mortality rate to >50%.

A common complication of untreated PAPVR is recurrent pneumonia. The chronic, increased pressure within the pulmonary venous system can lead to pulmonary vascular and cardiac remodeling with complications of arrhythmias, right-sided cardiac failure and pulmonary vascular disease (rare). These manifest themselves to varying degrees throughout life depending on shunt size, and may be the cause of morbidity and mortality from the disease.

Pulmonary Sequestration:

Pulmonary sequestration is a segment of nonfunctioning lung tissue that usually does not associate with the tracheobronchial tree (airways within the sequestration rarely communicate with the trachea) and receives all of its blood supply from an anomalous systemic artery. The table below distinguishes Scimitar syndrome from pulmonary sequestration. The main distinguishing points are the tracheobronchial communication and the venous drainage. There are two different types of sequestrations: intrapulmonary (formerly called intralobar) and extrapulmonary (formerly called extralobar), which collectively make up approximately 6% of congenital pulmonary malformations. The development of these abnormalities is hypothesized to be from the development of a primitive lung bud from the foregut during embryonic development.

Table 1 - Comparison of Scimitar syndrome and sequestration
Clinical Feature
Scimitar syndrome
Pulmonary sequestration
Located within the lung
Intrapulmonary-Yes, Extrapulmonary-Technically No
Arterial supply from systemic artery branch
Venous drainage into vena cava
Intrapulmonary-No, Extrapulmonary-Yes (or right atrium or azygous vein)
Airways communicate with trachea
May involve the entire lung (13)
Recurrent pulmonary infections
Intrapulmonary-Yes, Extrapulmonary-Usually No
Intrapulmonary-Yes, Extrapulmonary-Usually No

Intrapulmonary sequestrations are more common (75-90% of sequestrations) and are located within the lung tissue, usually in the posterior basal segment of the left lower lobe. This lesion usually occurs by itself with no associated congenital abnormalities and by definition, does not have a separate pleural covering. Communication with the tracheobronchial tree may occur via fistulas, but this is rare. 66% of lesions occur within the left lung and 99% are usually found in the posterior lung bases with venous drainage into the left atrium (4). The etiology of this lesion is unknown. Classically, intrapulmonary sequestrations do not present symptomatically until adolescence or adulthood. In fact, they are often an incidental finding on a chest X-ray performed for other reasons. When they do present clinically, it is with non-specific symptoms of cough, fever, wheezing, recurrent pulmonary infections, and rarely hemoptysis. Surgical resection of the lesion is curative and lobectomy is necessary because these are often poorly-defined masses.

Extrapulmonary sequestrations differ from intrapulmonary sequestrations in many respects: 1) the presence of a distinct and separate pleura, 2) the association with other congenital abnormalities (diaphragmatic hernia, colonic duplication, vertebral abnormalities, and pulmonary hypoplasia) (5), 3) >60% of cases present in infancy before age 6 months with a 4:1 male-to-female incidence, and 4) venous drainage is normally into the right atrium via the azygous system (11). The lesion is normally asymptomatic until associated abnormalities, infection, or shunting becomes severe. Although infants can present with cough, dyspnea, and difficulty feeding caused directly by the size of the lesion, a high degree of shunting will indirectly cause respiratory distress and CHF (7). Older children and adults usually present with chest pain and infection. Similar to intrapulmonary sequestration, if the patient is not diagnosed with an extrapulmonary sequestration during infancy because of no complications due to vascular causes (i.e., shunting), extrapulmonary sequestration will often be diagnosed as a result of an investigation for other associated anomalies. Complications are recurrent infection and hemorrhage in addition to those associated with other congenital abnormalities. Treatment is resection of the abnormality, which does not involve a lobectomy because it is a well-defined mass.

The anatomy can be further defined with the assistance of CT, MRI and angiography.

Physical examination reveals similar findings in both intra and extrapulmonary sequestrations:

1. Dullness to percussion over the lesion.

2. Decreased breath sounds over the lesion.

3. Rales may occur with a pneumonia.

4. Systolic murmur or continuous bruit associated with the arterial supply to the lesion may be present.

The differential diagnosis includes: 1) cystic adenomatoid malformation, 2) bronchogenic cyst, 3) bronchiectasis, 4) pulmonary atelectasis, 5) bronchial foreign bodies, and 6) pneumonia.

Scimitar syndrome and sequestration can both be categorized as venolobar syndromes. They both involve the lung, at least to some varying degree, and they both have cardiovascular involvement or at least the potential for cardiovascular involvement. However, while the cardinal cardiac lesion in Scimitar syndrome is partial or hemianomalous venous drainage, sequestration may not have an anomalous vascular connection. Sequestration is a disconnected or abnormally communicating bronchopulmonary mass or cyst with normal or anomalous arterial supply or venous drainage (12).

Sequestration is primarily considered to be a congenital lung malformation and because of the extra-parenchymal tissue, angiogenesis may occur causing an anomalous vascular supply. Scimitar syndrome, on the other hand, begins as a congenital cardiac malformation (usually an abnormal right pulmonary artery with or without other aberrant systemic arteries), which then causes abnormal lung development (ranging from minor abnormal bronchial branching all the way to a hypoplastic lung) and all of it is drained by the hallmark feature, an anomalous vein. In fact, bronchogenic cysts and extrapulmonary sequestrations have been found in association with Scimitar syndrome. It is because of these embryologic differences that on chest X-ray, sequestration usually appears as a cystic lesion or consolidation, while Scimitar syndrome has the characteristic Scimitar appearance with hypoplasia of the right lung.

For the above reasons, sequestration tends to be more of a condition for pulmonology specialists (pulmonology, CT, pediatric surgery), while scimitar syndrome tends to be more of a condition for cardiology specialists (cardiology, cardiac cath angiography, cardiovascular surgery).


1. What shunt fraction is considered clinically significant for the manifestation of symptoms in Scimitar Syndrome?

2. Why would you want to correct the underlying condition of scimitar syndrome early?

3. What are the complications of untreated pulmonary sequestrations?

4. What type of shunt is typical in extrapulmonary sequestration?

5. What type of sequestration is associated with a diaphragmatic hernia?

6. List three or more ways in which Scimitar syndrome differs from pulmonary sequestration.

Related x-rays

Scimitar Syndrome case: Rosen LM. Hemoptysis in a 11-Year Old: Scimitar Syndrome. In: Yamamoto LG, Inaba AS, DiMauro R (eds). Radiology Cases In Pediatric Emergency Medicine, 1996, volume 5, case 13. Available online at:

Pulmonary Sequestration case: Nakamura CT. Pulmonary Sequestration. In: Yamamoto LG, Inaba AS, DiMauro R (eds). Radiology Cases In Pediatric Emergency Medicine, 1996, volume 5, case 14. Available online at:


1. Halasz NA, et al. Bronchial and arterial anomalies with drainage of the right lung into the inferior vena cava. Circulation 1956;14:826-846.

2. Ericifskil J, et al. Non-surgical closure of anomalous artery supplying right lung lobe. Case Rep Clin Pract Rev 2001;2(2): 126-128.

3. Dupuis C, et al. The "adult" form of the Scimitar Syndrome. Amer J Cardiol 1992;70:502-507.

4. Larsen GL, et al. Chapter 17 - Respiratory Tract and Mediastinum. In: Hay WW, et al (eds). Current Pediatric Diagnosis and Treatment, 15th edition. 2001, New York: McGraw-Hill, pp. 449-450.

5. Bernstein D. Chapter 433.4 - Partial Anomalous Pulmonary Venous Return. In: Behrman RE, et al (eds). Nelson Textbook of Pediatrics, 16th edition. 2000, Philadelphia: WB Saunders, p.1367.

6. Stein RC. Chapter 384.5 - Pulmonary Sequestration. In: Behrman RE, et al (eds). Nelson Textbook of Pediatrics, 16th edition. 2000, Philadelphia: WB Saunders, p.1273.

7. Schnapf BM, et al. Pulmonary Sequestration. eMedicine Journal 2002:3(3).


9. Vaughan DJ, et al. Partial Anomalous Pulmonary Venous Connection. eMedicine Journal 2001:2(3).

10. Hughes JMB, Luce JM. Chapter 53 - Pulmonary Arteriovenous Malformations and Other Pulmonary Vascular Abnormalities. In: Murray JF, et al (eds). Textbook of Respiratory Medicine, 3rd edition. 2000, Philadelphia: WB Saunders, pp. 1557-1573.

11. Krummel TM. Chapter 14-Congenital Malformations of the Lower Respiratory Tract. In: Chernick V, Boat TF (eds). Kendig's Disorders of the Respiratory Tract in Children, sixth edition. 1998, Philadelphia: W.B. Saunders Co, pp. 311-317.

12. Clements BS. Chapter 72-Congenital Malformations of the Lungs and Airways. In: Taussig LM, Landau LI (eds). Pediatric Respiratory Medicine. 1999, Carlsbad: Mosby, pp. 1123-1128.

13. Samson RA. Personal Communication. 2003.

Answers to questions

1. >2:1 pulmonary flow to systemic flow.

2. To prevent future complications such as: pneumonia, arrhythmia, and irreversible pulmonary hypertension (13).

3. Recurrent pulmonary infections, bronchiectasis and hemorrhage.

4. Typically, it is left-to-right venous drainage: systemic artery to the systemic venous system. Intrapulmonary sequestrations typically shunt systemic blood to the pulmonary vein (systemic artery to the pulmonary vein, which is left to left).

5. Extrapulmonary sequestration (30% are associated with diaphragmatic hernias).

6. 1) Sequestration contains bronchi that do not communicate with the trachea. 2) Two types of sequestration (intrapulmonary and extrapulmonary). 3) Dextrocardia and ASD usually accompany Scimitar syndrome. 4) Intrapulmonary sequestration venous drainage enters the left heart, while the venous drainage of Scimitar and extrapulmonary sequestration enters the right heart circulation.

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