Imaging congenital lesions of the respiratory tract (2024)

Abstract

Congenital lung lesions comprise a wide variety of uncommon conditions, some of which can be serious, e.g. vascular ring malformations, and some of which are usually benign such as pleural effusions. The natural history of other lesion types, probably comprising the largest group, has yet to be clearly defined.

A number of congenital respiratory tract malformations are detectable prenatally during routine ultrasound and a large proportion of these will be postnatally asymptomatic. These neonates pose management dilemmas and care is needed to avoid over-investigation and treatment owing to associated attendant parental anxieties.

This paper describes a number of conditions with case illustrations, concentrating on clinical presentation, imaging modalities and management principles. Patients have been subdivided into three groups: prenatal presentation, overt symptoms at birth, and presentation in childhood. Inevitably there will be some overlap between these groups.

Embryology

Respiratory tract development begins in the 4th week of gestation but is not complete until the 8th year of life. Bronchi and terminal bronchioles form between the 5th and 17th weeks, respiratory bronchioles and alveolar ducts at 16–25 weeks and terminal sacs (primitive alveoli) at 24 weeks plus. After birth respiratory bronchioles and alveoli increase in number until 8 years of age. The embryonic defects for most of the conditions discussed in this paper occur during or after the 6th week [1].

In order for lungs to develop normally in utero, adequate space is required within both the fetal chest and the maternal uterus. Oligohydramnios, or space occupying lesions, within the chest will prevent normal lung development and cause pulmonary hypoplasia. In addition to normal anatomical development, surfactant is necessary to optimize physiological lung function. Surfactant is produced by type 2 alveolar cells from 20 weeks, but the quantity is insufficient in premature infants less than 34 weeks of gestation. Furthermore, surfactant production is reduced by infection and interference with lung development as a whole. There is a rare protein B deficiency disorder that is manifest by surfactant deficiency.

Prenatal presentation

With the constantly improving resolution of ultrasound equipment and the increasing skills of sonographers, this group of prenatally diagnosed patients is now significant and includes a heterogeneous group of pathologies. Diagnosis depends on the loss of normal anatomical landmarks of the “four chamber” heart at 45° to the spine with hom*ogeneous lung either side. Lesions with a space occupying effect such as cystic adenomatoid malformations (CAM), sequestrations and diaphragmatic hernias are those most commonly seen. Prenatally these lesions are usually echogenic, containing cystic lucencies of varying sizes. Other features may help to narrow the differential diagnosis. Congenital diaphragmatic hernia is the most frequently diagnosed thoracic malformation. In left-sided hernia, the stomach bubble will be absent below the diaphragm and later in pregnancy peristalsis may be seen in the herniated bowel loops in the chest. On colour flow Doppler, a vessel seen arising from the aorta supplying the lesion is the pathognomonic prenatal finding of a sequestration [2] (Figure 1). Sequestrations are commonly associated with other abnormalities, unlike CAM. Other conditions such as congenital lobar emphysema, which may be seen as unilateral lung expansion with a slight increase in lung echogenicity and tracheal/laryngeal stenosis, with bilaterally over-expanded and echogenic lungs can also present prenatally. The presence of even severe midline shift can regress during pregnancy, but the presence of hydrops is usually a poor prognostic indicator in all these conditions (Figure 2). Unilateral lung agenesis also causes severe midline shift and may be associated with major abnormalities in other systems, particularly vertebral anomalies. The absence of a stomach bubble on prenatal scanning is strongly predictive of isolated oesophageal atresia (OA). In the majority of cases of OA the stomach will be visible owing to an associated tracheo-oesophageal fistula and prenatal diagnosis will not be possible. Pleural effusions in utero are also easily seen and can regress. They are associated with chromosomal abnormality, such as Turner's and Noonan's syndromes, in 10% of cases. Once a chromosomal problem has been excluded pleural effusions are only problematic if they are large, present early and do not resolve, making associated lung hypoplasia likely. Rare conditions such as skeletal dysplasia can cause lung hypoplasia secondary to short ribs. These tend to be lethal dysplasias such as thanatophoric dysplasia, osteogenesis imperfecta type 2, polydactyly short rib syndrome and asphyxiating thoracic dysplasia (Jeune syndrome).

Overview and postnatal imaging

The imaging of infants with prenatally detected abnormalities depends upon symptoms at birth and is controversial in the asymptomatic group. Up to 30% [2] (49% in our experience) of parenchymal lung abnormalities regress in utero and a high percentage will be asymptomatic at birth. The approach to postnatal imaging is variable countrywide and is often led by the paediatric surgeon and their attitude to follow-up and treatment of this group. Chest radiography will often reveal an abnormality, which may be subtle, but in some cases the radiograph will be normal. In our experience, further investigation with cross-sectional imaging will always reveal an abnormality (Figure 3), but whether such imaging is warranted is debatable. In general, further investigation is necessary in all symptomatic infants and is also advisable in the asymptomatic group, particularly when chest radiography shows a definite abnormality. In addition to the location and characteristics of an abnormality, the surgeon is most interested in identifying any abnormal vascular supply and other associated abnormalities.

The term bronchopulmonary foregut malformation encompasses a number of abnormalities [3]. These include primitive foregut malformations and CAM or lung bud abnormalities, which may occur in association with abnormal pulmonary vasculature, i.e. pulmonary sequestrations. A high percentage of bronchopulmonary foregut malformation were previously thought to present in the first year of life, but the new population of prenatally diagnosed lung lesions may alter this perception.

Pulmonary sequestrations are regions of abnormal lung parenchyma that do not have normal communications with the tracheobronchial tree or pulmonary arteries. They are supplied by either the thoracic or abdominal aorta [4]. There are two distinct types described, extralobar and intralobar. Extralobar sequestrations are least common (25%). They have their own pleural covering and abnormal venous drainage via the hemiazygous, azygous, portal vein or inferior vena cava. They are situated between the diaphragm and the lower lobe (commonly left), although infra-diaphragmatic suprarenal lesions can occur. Up to 50% of all pulmonary sequestrations have an associated diaphragmatic abnormality and cardiac, rib and vertebral abnormalities are not uncommon. A pulmonary sequestration can also be associated with other congenital thoracic lesions including oesophageal duplication, communication with the oesophagus and tracheobronchial tree, bronchogenic duplication cyst, CAM, congenital diaphragmatic hernia and congenital heart disease, hence the term bronchopulmonary foregut malformations. In utero hydrops, polyhydramnios and isolated pleural effusions on the affected side can be seen. Cardiac failure secondary to increased circulatory requirements can occur postnatally. Intralobar sequestrations are contained within normal visceral pleura and have normal venous drainage into pulmonary veins. Some do have bronchial communication. Considerable overlap between the two groups of pulmonary sequestration is now accepted.

CAM are hamartomatous lesions, which may communicate with the bronchial tree and have normal blood supply. Hybrid abnormalities of CAM and sequestration are increasingly recognized. Symptoms are varied, ranging from none to slight respiratory distress to full-blown respiratory distress requiring ventilation and even circulatory embarrassment.

The initial investigation is chest radiography. As previously mentioned, if the lesion has regressed in utero the radiograph may be normal or very subtly abnormal. If the lesion was easily visible throughout prenatal scanning it is usually obvious postnatally and may well be large and cause midline shift. These large lesions usually result in early postnatal respiratory distress.

The majority of these bronchopulmonary malformations, whether mixed lesions, sequestrations or CAM, will have solid regions with or without air-filled cystic areas depending on how soon after birth an X-ray is taken. The differential diagnosis is of congenital diaphragmatic hernia, which is occasionally misdiagnosed prenatally or can be seen in combination with a lung lesion. A lateral chest radiograph may be helpful. Ultrasound is the next investigation of choice; it is non-invasive, quick and can be performed at the cot side in the sick neonate. Peristalsing bowel within the chest or liver/spleen may be seen along with the absent diaphragmatic leaf. The abnormal lung lesion may be seen if it is mainly solid and adjacent to the diaphragm. The most important assessment is of the aorta, to look for abnormal feeding vessels, which are often sizeable. Colour flow Doppler is helpful for this.

Follow-up investigations depend on symptoms and local paediatric surgical management. In the symptomatic neonate, further investigation with cross-sectional imaging is necessary. MRI is the first line of investigation but availability, difficulty with sedation (or general anaesthetic) and length of examination makes the use of CT more common. MRI is useful for the further assessment of diaphragmatic problems on account of being able to image in coronal and sagittal planes. These imaging planes are also particularly useful when attempting to demonstrate abnormal aortic feeding vessels associated with pulmonary sequestration. Gadolinium enhancement and both cardiac and respiratory gating are necessary. CT scanning has the disadvantage of exposure to ionizing radiation, which will be high if thin slices are performed to reconstruct in the coronal/sagittal planes. In addition, CT requires iv contrast medium. Localization of the lung lesion and resolution of the lesion itself is superior in CT. It may be necessary to perform angiography if vascular anatomy cannot be clarified by cross-sectional imaging.

Occasionally, suspicion of an associated neurenteric/duplication cyst may warrant upper GI contrast studies and assessment of the spinal canal with MRI. The contrast swallow is considered the most helpful investigation in the investigation of suspected bronchopulmonary foregut malformations [3].

Bronchography is rarely performed. In CAM it may show abnormal truncation of the bronchial tree at the site of the abnormality, whereas in sequestration there will be displacement and draping of the bronchial tree over the lesion. Communication between bronchial tree and oesophagus is usually shown by contrast swallow.

Management

If prenatal regression is seen the pregnancy can be managed normally with radiography performed in the postnatal period.

If the lesion remains visible throughout pregnancy, and in particular there remains midline shift, in utero transfer to a centre with paediatric anaesthetic and surgical support is advised. These neonates are more likely to be symptomatic at birth and operative intervention is common [5]. Debate exists about the asymptomatic cohort, whether with a normal or abnormal chest X-ray. In the USA an abnormality is pursued and operative intervention is the norm. In the UK there is an increasing tendency not to operate unless there are symptoms, even in the presence of an abnormal X-ray. This group of patients may never have presented at all were it not for prenatal ultrasound examination and many consider it meddlesome to intervene. In our institution these patients are followed-up long-term and the surgeon will only intervene if the child becomes symptomatic with recurrent infections or other respiratory symptoms. There is another school of thought that a high percentage of these asymptomatic neonates will present with recurrent infection and should therefore be operated upon, but this is unpredictable and unquantified [6]. In addition there is a risk, yet to be quantified in this group, of malignancy developing in the congenital lung lesion [7]. The debate will continue until there is long-term follow-up of a large cohort in this group.

Overt symptoms at birth

Many conditions that are not diagnosed prenatally can present at birth with severe respiratory distress. These include tracheomalacia, isolated or associated with an underlying abnormality such as oesophageal atresia or tracheo-oesophageal fistula, a vascular ring malformation, or rare conditions such as tracheal stenosis and laryngeal cleft. These conditions usually present with noisy breathing, namely stridor related to inspiration. Dyspnoea, cyanosis and “near death” episodes related to feeding suggest any of the above diagnoses.

Laryngeal atresia may be picked up prenatally as previously mentioned. If it is not, it presents at birth with a cyanosed neonate and an inability to intubate.

The normal trachea has a large range of normal diameters, dilating on inspiration, narrowing on expiration and collapsing on cough and Valsalva manoeuvre [8]. Tracheomalacia is due to hypoplasia or dysplasia of the anterior tracheal cartilages, which cause occlusion of the trachea even in normal inspiration. There is a spectrum of severity.

In oesophageal atresia, the proximally dilated pouch causes compression on the upper trachea in utero and therefore causes secondary tracheomalacia. In 75% of infants with oesophageal atresia there is a distal fistula between the tracheobronchial tree and oesophagus, with air entering the stomach and small bowel. This abnormality is generally not detected prenatally, in contrast to infants with oesophageal atresia without fistula. Oesophageal atresia without fistula is less common but may be suspected prenatally on account of associated polyhydramnios and absent stomach. Both the above conditions can have a proximal pouch fistula. The rare H-type fistula abnormality is an isolated tracheo-oesophageal fistula without oesophageal atresia and can present later in childhood with repeated chest infections secondary to aspiration. This can also occur following surgery for oesophageal atresia when a proximal fistula is missed.

Vascular ring malformations are anomalies of the aortic arch. The majority present in neonatal life, although occasionally they can present later as a viral infection tips the balance of respiratory reserve. Embryologically, the 4th branchial arch forms the aortic arch and the 6th arch forms the pulmonary artery and ductus arteriosus. There are many types of major vessel malformation and the system of classification most relevant to radiologists is that related to appearances on contrast swallow, which is the lynch pin of diagnosis. The ring is usually closed by the ductus arteriosus, which may be a fibrotic structure at the time of diagnosis and not a true functioning vessel.

Congenital tracheal stenosis is a narrowing of the trachea caused by complete tracheal cartilaginous rings [9]. It is associated with other conditions such as bronchial stenosis, tracheal bronchus, H-type fistula, lung hypoplasia or agenesis, pulmonary sling and bridging bronchus [10]. The main narrowing is below the subglottic region, which is of normal calibre in this condition but always affected in acquired tracheal stenosis secondary to previous intubation [9].

Another rare group of conditions presenting at or around birth are those causing secondary abnormality of lung parenchyma. These include pulmonary lymphangiectasia, anomalous pulmonary venous drainage and protein B deficiency.

Pulmonary lymphangiectasia is due to abnormal development of the lymphatics in the subpleural and interlobar connective tissue [11]. It is a poorly documented condition that more commonly affects males and is seen in asociation with Noonan's, Turner's and Down's syndrome. The primary condition presents in the neonatal period with increasing respiratory compromise and recurrent pneumonia and cough. Parenchymal abnormality is associated with chylothoraces and prognosis is poor with a high mortality. However, if the neonatal period is survived, slow improvement can sometimes occur.

Pulmonary venous obstruction secondary to anomalous pulmonary drainage will give a similar appearance. This condition however can be unilateral.

Protein B deficiency is characterized by an inability to produce surfactant. A full-term infant will show appearances identical to respiratory distress of the newborn. Unfortunately this condition is fatal although in a few cases in the USA, heart-lung transplantation has been attempted.

Imaging

The initial chest X-ray may appear normal or show air trapping and overinflation. In some types of vascular ring there may be a difference in lung translucency as one bronchus may be preferentially compressed by the abnormal vasculature. Siting of the aortic arch should be attempted on plain radiography and any other tracheal indentation or displacement noted. Usually the trachea is slightly displaced to the right by the normal left aortic arch. A lateral X-ray will occasionally reveal a soft tissue mass between trachea and oesophagus of an aberrant, left pulmonary artery or obvious narrowing of the trachea in tracheo-bronchomalacia.

In suspected oesophageal atresia, X-ray following insertion of a weighted nasogastric (NG) tube (Replogal) will show the tube coiled in the upper pouch. If there is no associated tracheo-oesophageal fistula the stomach bubble will be absent. However, if a fistula is present, gaseous distension of bowel in the abdomen will be prominent. Looking for associated rib and vertebral anomalies will help in the diagnoses of VATERL association and other syndromes. A high tube potential filtered radiograph will give good definition of the tracheo-bronchial tree and the normal aortic indentation and normal bronchial situs [12]. It will also be helpful in assessing congenital tracheal stenosis, although in this condition CT has been found to be superior [9].

A prone contrast oesophagram is performed in our institution if a tracheo-oesophageal fistula is suspected. The neonate must be monitored for oxygen saturation during the procedure and medical support, oxygen and suction should be readily available. The procedure is video recorded and rapid sequence images can be taken. In our institution water-soluble, low-osmolar contrast medium is injected via a NG tube as the tube is slowly withdrawn. This achieves good distension of the oesophagus and the prone position maximizes the chances of outlining the fistula. However, some institutions have abandoned the prone position suggesting it too hazardous. Bronchoscopy is useful to look for an associated upper pouch fistula in infants with oesophageal atresia.

A conventional well distended upper GI contrast study will show an abnormal oesophageal indentation in the majority of infants with a vascular ring, or at least give rise to enough concern to warrant further assessment with another investigation. There are four patterns of indentation described. (1) Anterior compression of the trachea with a normal oesophagus. This is due to a normal innominate artery and can be seen during fluoroscopy of the trachea. This is not usually symptomatic and surgery is not usually indicated. (2) Anterior tracheal compression and posterior oesophageal compression. This is due to a double aortic arch formed by a right-sided aortic arch and aberrant left subclavian artery with a left descending aorta, a patent ductus closes the ring. Occasionally the left main bronchus may be compressed rather than the trachea, leading to hyperlucent left lung owing to air trapping. Usually one side of the double arch is dominant and larger. (3) Posterior tracheal and anterior oesophageal compression. This is caused by an aberrant left pulmonary artery, which causes a sling behind the trachea as it courses to the left (Figure 4). There is a soft tissue mass seen between trachea and oesophagus and the differential of this appearance is one of a bronchogenic cyst or of enlarged lymph nodes. This abnormality is occasionally associated with a right upper lobe tracheal bronchus and associated right upper lobe over-inflation. (4) Normal trachea with posterior oesophageal indentation. This is the most common finding and is due to an aberrant right subclavian artery or aberrant left subclavian artery on a right-sided arch. This is generally asymptomatic and causes oblique indentation of the oesophagus.

Once a vascular ring is suspected from the oesophagram, confirmation is required. MRI or MRA will usually give all the information required. Even if cross-sectional imaging, preferably with MRI but CT with contrast can also be used, gives adequate demonstration, the cardiac surgeons may still require angiography prior to surgical repair as the vascular anatomy may be complex. Bronchoscopy may be helpful in this group if there is a suggestion of associated tracheobronchial abnormality. However, this can be dangerous in an already severely compromised airway. Bronchography may also be helpful in assessing associated tracheobronchial abnormalities such as a right upper lobe tracheal bronchus.

The diagnoses of pulmonary lymphangiectasia, anomalous pulmonary venous drainage and protein B deficiency are suspected on chest radiograph appearances. Interstitial shadowing, with or without effusions, will be seen in lymphangiectasia and anomalous pulmonary venous drainage. An initial alveolar picture becoming interstitial with time is seen in protein B deficiency. Anomalous pulmonary venous drainage can be subtle on echocardiography and it is worth repeating the investigation if doubt remains. The diagnosis of lymhangectasia and protein B deficiency is generally confirmed by lung biopsy.

Management

Mild to moderate primary tracheomalacia can respond to physiotherapy and may improve spontaneously as the child's airways grow, usually around 4–5 months. In premature infants, respiratory support with ventilation and NG tube feeding with slow weaning of the ventilator may suffice. Otherwise, aortopexy with operative fixation of vascular structures onto the manubrium sterni, preserving the connective tissue between the artery and trachea in order to pull the trachea forward, may be necessary [13]. This is less effective in primary than secondary tracheomalacia. In more severe cases, tracheal resection and endotracheal stenting may also be considered as therapeutic options. Symptomatic vascular ring malformations need operative intervention, usually by ligation of the non-dominant arch. Tracheo-oesophageal fistulae, with or without oesophageal atresia, require primary surgical correction. Interposition with stomach or colon may be necessary if the proximal and distal oesophageal sections are short. Even if primary anatomoses is possible, complications with reflux and aspiration owing to abnormal oesophageal peristalsis or recurrent fistula formation may develop.

Late presentation: 6 months–16 years

This group contains CAM and sequestrations not diagnosed prenatally that become symptomatic, along with other conditions such as bronchogenic cysts, unilateral hypoplastic lung, Scimitar syndrome and congenital lobar emphysema (CLE).

CLE can be picked up prenatally [14]. However, in our experience this is not common and may be owing to the less prominent echogenicity of the abnormal fetal lung compared with some other lesions. Although, as previously mentioned, CLE can present at birth with respiratory compromise secondary to increasing air trapping, it can present later in childhood with infection and respiratory compromise or as an incidental finding on chest radiography performed for persistent cough. 20% of congenital lobar emphysema is associated with congenital heart disease. The underlying aetiology is still unclear but is thought to range from a developmental abnormality of alveoli, including polyalveolar lobe [15], i.e. an increase in number of otherwise normal airways and alveoli, obstruction of the bronchus by a mucus plug in utero or dysplastic bronchial cartilage in the affected lobe. Previously CLE was also thought to occur as a result of bronchial atresia. However, bronchial atresia is now considered to be a separate entity. The radiological appearances of bronchial atresia are varied and most commonly affect the left upper lobe. They include areas of focal hyperinflation, possibly associated with a medial opacity or cyst owing to fluid in the obstructed bronchus, or as a fluid filled lobe-suggesting tumour on chest radiography.

CAM, sequestration and other congenital lesions such as lung cysts can present at any age with recurrent infection and lack of resolution of radiographic changes (Figure 5). It is important to always consider the possibility of a previously dormant congenital lung lesion as a cause for symptoms and radiographic findings.

Unilateral lung hypoplasia is often asymptomatic and may again be found on routine chest radiography (Figure 6). Scimitar syndrome is unilateral lung hypoplasia on the right side combined with abnormal venous drainage into the systemic system. Drainage is usually by a large solitary vein, the “Scimitar”. This syndrome may be asymptomatic or present with repeated infections. Occasionally, if the draining vessel is large, it can present in infancy with heart failure secondary to the large shunt. It is part of the sequestration spectrum.

H-type tracheo-oesophageal fistulae can present in later childhood secondary to recurrent aspiration and infection. There may be established bronchiectasis by the time the condition is diagnosed.

Bronchogenic cysts may be small and asymptomatic and suddenly grow significantly in size causing collapse of a lobe or obstructive emphysema. They may present with recurrent infections or even central airway symptoms. The main differential is of mediastinal lymph node enlargement or of foreign body aspiration. Again, a delay in diagnosis may be significant if the possibility of bronchogenic cysts is not considered.

Imaging

On chest radiography in unilateral lung hypoplasia, the small lung will be hyperlucent with decreased vascular markings secondary to the associated ipsilateral hypoplastic pulmonary artery and there will be some midline shift to the affected side. Echocardiography to assess pulmonary arterial size can be helpful. Expiratory and inspiratory films will not show air trapping. Radionuclide ventilation-perfusion scanning will show both reduced ventilation and perfusion in the small lung. In Scimitar syndrome the appearances of a hypoplastic lung are accompanied by the Scimitar-like opacity of the anomalous draining vein coursing below the diaphragm to drain into the inferior vena cava. Ultraound to confirm the Scimitar vein is usually followed by angiography for further confirmation and to look for any associated anomalous arterial supply.

In congenital lobar emphysema the chest radiograph is the main examination with inspiratory and expiratory films taken to assess for air trapping. In contrast to pulmonary hypoplasia, the affected lobe will be over expanded causing collapse of adjacent lobes and there may be shift of the mediastinum away from the affected hypertranslucent lung. On an expiratory chest radiograph the over expanded lobe will show no volume loss and will remain hyperlucent. Occasionally lateral decubitus films may be helpful if an expiratory film cannot be obtained; the affected lobe will remain hyperinflated when in the dependent position. Ventilation and perfusion radionuclide scanning is very helpful in older, cooperative children. It will show reduced perfusion and significant reduction or absence of “washout” of tracer on delayed ventilation scans. The possibility of an inhaled foreign body should always be considered where there is unequal translucency or size of the lungs as seen in both pulmonary hypoplasia and congenital lobar emphysema. Bronchoscopy to exclude foreign body aspiration is advised, particularly in the presence of air trapping.

A contrast swallow should be performed to look for an H-type fistula when suspected, although in older patients prone swallows are not always practical. Good oesophageal distension is of great importance in order to demonstrate a fistula. Bronchoscopy may also be performed to exclude this diagnosis. A contrast swallow may also show extrinsic compression of the oesophagus and tracheobronchial tree, indicating a possible vascular ring or bronchogenic cyst as the cause of the child's symptoms. MRI and contrast enhanced CT are particularly useful for further assessment of possible underlying congenital thoracic abnormalities, especially those giving rise to an abnormal mediastinal contour on chest radiography, e.g. to differentiate a bronchogenic cyst from lymph node enlargement. However, we have found it unhelpful and confusing in congenital lobar emphysema.

Management

Surgical intervention is required for most of these conditions that have become symptomatic; resection of the affected lobe in lobar emphysema, CAM, sequestration and bronchogenic cyst or the fistulous tract in the H-type fistula. It is important to be confident that the possible co-existence of any associated abnormalities of bronchopulmonary foregut malformations or complex hybrid lesions have been considered prior to surgery. In unilateral hypoplastic lung, long-term follow up to assess the developing chest deformity and associated scoliosis is advised.

Conclusion

Congenital respiratory tract abnormalities are a group of diverse pathologies. Diagnosis rests initially on symptoms and plain radiographs. The need and type of further investigations is governed by the most likely considered diagnoses on assessment of age of the patient, symptoms and initial radiographs. It is important that, particularly in the older age groups, congenital thoracic lesions are considered in the differential in the interpretation of an abnormal chest radiograph. Prenatal ultrasound has presented a new group of patients who would previously have gone undetected and the issue of their best management is still under debate.

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