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Pulmonary sequestration (PMS) is a rare bronchopulmonary malformation. It has an incidence of between 0.15% to 1.7%. Likewise, cystic adenomatoid malformation (CCAM) is another relatively rare category of a bronchopulmonary malformation with a reported incidence of between 1 in 25,000 to 1 in 35,000. Moreover, a bronchopulmonary malformation with features allied to both of these forms is considered an even rarer entity. In general, bronchopulmonary malformations present with a range of non-specific symptoms. Radiological features can be non-specific yet distinctive when related to clinical features. Ultimately, definitive diagnosis depends upon histological assessment of lung tissue. We present an adult female with radiological features of both pulmonary sequestration and cystic adenomatoid malformation. This was an incidental finding unrelated to the patients presenting complaint. This case highlights the importance of using a structured and systematic approach when interpreting medical imagery.
A 30-year-old Caucasian female was referred to the Gastroenterology Clinic with intermittent post-prandial left iliac fossa pain. In addition, she also described recently having loose stools and suffering with generalised joint pain. Her past medical history was significant for a longstanding history of loose stools and abdominal pain. This was previously investigated by means of a magnetic resonance imaging (MRI) and colonoscopy. Following this a diagnosis of Crohn’s disease was made in 2001. Subsequently, she was successfully medically treated for her Crohn’s disease. However, in 2014 following an episode of abdominal pain she had a laparotomy which revealed no abnormalities. Nevertheless, she continued to follow a strict FODMAP diet in an attempt to alleviate what was considered to be her functional gastrointestinal symptoms. The only additional report from her past medical history included a single incidence of left sided pneumonia which required a hospital admission and raised an unconfirmed diagnosis of bronchiectasis. There were no other overt complaints or written documentations of any other respiratory symptoms.
On examination, she weighed 48.55kg, was not pale or jaundiced. There was no evidence of peripheral lymphadenopathy and her abdomen was soft and slightly tender in both iliac fossae. No mass or organomegaly was identified. At the time the best course of actions was determined as to explore whether her Crohn’s disease was active and the extent of any active Crohn’s disease.
Accordingly, investigations ordered included, full blood count, haematinics, liver function test, renal function test and inflammatory markers. However, these investigations were all within normal range. In addition, a MRI was also requested and distribution showed normal enteric structures. However, a 5cm haemorrhagic right ovarian cyst and several very small corpus luteal cysts were incidentally identified; potentially explaining her pelvic discomfort. Moreover, a further unexpected yet interesting observation was made. In particular, an anomalous artery was identified (figure 1). The artery was noticed as originating from the coeliac axis and supplying the lower lobe of the left lung. Subsequently, computed tomography (CT) of the chest with CT angiography was recommended and this established the presence a bronchopulmonary malformation (figures 2, 3A and 3B). In particular, a rudimentary bronchial tree was identified which did not appear to communicate with the main tracheobronchial system. Furthermore, it also appeared to be partially occluded by debris. Additionally, observed within this segment of lung were numerous small cysts ranging from 0.2cm to 2cm in size. These features are recognised radiological features pertaining to both PMS and CCAM. Accordingly, a hybrid type malformation is suspected.
In 1946 Pryce  first coined the term and identified the anatomy of a pulmonary sequestration (PMS). He specified that a PMS comprised a distinctive segment of lung, which could be a bronchopulmonary mass or a cyst, satisfying two conditions. Firstly, that it exists dissociated from the normal tracheobronchial tree and, secondly, that it be in receipt of an arterial blood supply from one or more systemic arteries as opposed to the customary pulmonary vessels . Furthermore, PMS are also categorised as either intralobar or extralobar. The former arises when visceral pleura is shared between normal lung tissue and adjacent abnormal tissue [1–3]. This is in contrast to the latter which occurs when there is a separate independent pleura encasing the abnormal lung viscera [1–3]. This differentiation is understood to be consequential to the particular embryological stage at which the fault in foetal lung and vasculature development arises . Nonetheless, this is a very rare malformation with an incidence believed to be in the range of 0.15% to 1.7% . On the other hand, congenital cystic adenomatoid malformation (CCAM) is another form of brochopulmonary malformation . It is considered a intraparenchymal lung disease characterised by the absence of normal alveoli and the presence of multiple variably sized cysts present within a segmental area of lung tissue [5,6]. It was first described by Chin and Tang in 1949 and is reported to have an estimated incidence of between 1 in 25,000 to 1 in 35,000 pregnancies [5–7]. CCAM can be classified into one of three categories depending upon the clinical, radiological and pathological assessments of the abnormal lung parenchyma [5,7]. Furthermore, in contrast to pulmonary sequestrations, CCAMs are typically connected to the normal tracheobronchial tree and draw blood from the normal pulmonary circulations .
Hybrid IPS and CCAM are relatively rare brochopulmonary malformations with no reported incidence ,. Here we have presented a case report of a young female demonstrating radiologically features of both intralobar pulmonary sequestration (IPS) and CCAM. To the best of our knowledge this is the first case report describing an adult with a IPS, with certain features of a CCAM, in receipt of an anomalous vessel arising from the celiac artery.
If we are to adhere specifically by Pryce’s  original description of a PMS a hybrid lesion should be viewed as a IPS with accompanying CCAM features. With regards to our case, we incidentally uncovered a left sided bronchopulmonary malformation involving an abnormal artery arising from the coeliac trunk. From a radiological perspective, this malformation has features of both ILS and CCAM, therefore, it is described as a hybrid type malformation. They have previously been recognised and described in the literature to a limited extent. In 1979, Savic’s analysis of 100 pathology reports identified that bronchiectatic forms of IPS can exist with polycystic features. Furthermore, in 1997 Cass described treating patients who had IPS with CCAM features. Between 1949 and 1999, 36 cases of pulmonary sequestration associated with CCAM have been described. More recently there have been a number of case reports documenting the descriptions of a PMS with features of CCAM [9–18]. However, the majority of these describe a extralobar pulmonary sequestration (EPS) malformation. We were only able to identify 7 cases pertaining to a IPS with CCAM associated features, [6,11,12] none of which refer to an aberrant artery arising from the celiac artery.
Regarding ILS, it is understood that the posterior basal segments of the lower lobes are the most commonly effected zones [19–21]. In addition, left sided malformations are reported in the literature to be more frequent than right sided [19,21]. In general, the arterial blood supply for ILS is thought to arise from the descending thoracic artery 74% of the time compared to 19% originating from the abdominal aorta . Although one of the earliest reports of an anomalous artery, associated to an ILS, arising from below the level of the diaphragm was described by Pryce in 1946 . Since 1946 we have been able to identify a number of reports which describe a ILS consisting of an anomalous artery derived from the celiac trunk [19,22–32]. Interestingly, the majority of the reports that we have identified refer to a right sided ILS with a celiac artery derived feeder vessel. We were only able to identify 3 reports that describe a left sided ILS with an anomalous celiac artery derived blood supply [29–31]. This would be the fourth report of a left sided ILS with a celiac artery derived bloody supply.
ILS appears to encompass a spectrum of clinical presentations[1–3]. In particular, presentations can range from an incidental finding in an otherwise asymptomatic individual to individuals who suffer with chronic bouts of bronchitis and recurrent pneumonia[1–4,21,33]. Particular symptoms which may be observed include chest pain, dyspnoea and haemoptysis [20,25,27,34,35]. Due to a combination of non-specific presenting symptoms, coupled with the rare nature of PMS, a misdiagnosis rate of 87% has been recognised . The majority of cases of ILS are diagnosed in the second decade of life and are rarely diagnosed in those older than 40 [2,33]. Overall, there is no gender predilection [1,2] although with advancement in age there appears to be a preference towards males being diagnosed with ILS .
A variety of imaging modalities can be utilised during the assessment of a potential PMS. Doppler ultrasonography (DUS) is an effective imaging modality for the antenatal identification of a PMS. DUS has the capability to recognise an aberrant vessel that may be feeding an abnormal lung mass which is perceived as an abnormal area of echogenicity. However, antenatal diagnosis requires serial imaging which can occasionally inaccurately demonstrate a disappearing lesion which is actually present postnatally[8,37]. In addition, it can be difficult to establish a diagnosis when using DUS as no specific PMS signs exist[7,8]. Chest radiography is a frequently used investigation for patients presenting with respiratory symptoms[20,25,27,35]. It is quick to perform, widely available, relatively cheap, and can direct the requirement for further investigation, consequently it is generally used as a first line investigation[20,25,27,35]. Common signs observed on a chest radiograph include radiopaque areas which may be indicative of nodules, reticular infiltration or masses[20,35]. These radiographic findings are frequently confused with other lung conditions such as pneumonia [35,36]. Hence, due to the non-specific nature of these radiographic signs and lack of capacity for the identification of vasculature, chest radiography is not considered to be specific enough when attempting to diagnose a PMS. CT imaging is commonly used when further assessment of the lung parenchyma is deemed necessary and to establish a definitive diagnosis of a PMS [20,21,29,35]. CT imaging is better able to delineate the anatomy of a suspected PMS [20,36]. Anatomical structures which can be identified on CT include a lung mass, a cyst and a fluid or air filled cavity [20,36]. Moreover, contrast enhanced CT imaging and CTA are considered the modalities of choice for the identification of arterial vasculature. In particular, with CTA vessels are demarcated as they are filled with contrast. This component of imaging, when factored in with the identification of the lung lesion, is fundamental for a definitive PMS diagnosis. Interestingly, pulmonary angiography is considered the gold standard for the diagnosis of a PMS . Nevertheless, CTA and magnetic resonance angiography (MRA) are utilised more often. This is for a number of reasons; firstly, CTA and MRA are less invasive. Secondly, both are able to identify the arterial vasculature to a good level of detail and are considered to give superior information with regards to the lung parenchyma. Finally, they are considered safer alternatives .
When a diagnosis has been established, active management is usually considered the best option –. Surgical resection, in particular an open lobectomy, is the mainstay of treatment for IPS and offers a good prognosis [20,21,35]. It is considered for all patients that are symptomatic and suitable for surgery . The earlier surgery is performed the better the prognosis for two main reasons. IPS is associated with chronic pulmonary infection which from a septic point of view may be fatal . In addition, longstanding pulmonary inflammation can destroy the lung parenchyma , both sacrificing lung function and ultimately making surgery more challenging due to the loss of surgical margins, risking a larger resection . In those who are asymptomatic, the benefits of surgery have been disputed . However, due to the risk of recurrent infection and subsequent need for a larger resection surgery is generally encouraged, nevertheless, conservative management may also be considered as an option in those who are asymptomatic . Novel therapeutic options which have been explored include the endovascular occlusion of the anomalous vessel and resection via minimally invasive techniques such as video assisted thoracoscopic surgery [29,36].
With regards to intralobar pulmonary sequestration the following differential diagnoses are considered: bronchiectasis, bronchogenic cysts, empyema, lung abscess, pneumonia and pulmonary neoplasm. Due to the relative commonness of these diagnosis interpretation and description of imaging has been more commonly established. In the majority of cases a chest radiograph is performed in the first instance as it is quick and provides important initial details. CT and MRI are subsequently performed as second line investigations if more detail is warranted.
The chronic airway dilatation and mucus secretion which occurs in bronchiectasis results in alteration in the lung parenchyma which can be observed on chest radiography and CT imaging . When considering chest radiography, tram-track opacities which can be observed are produced by thickened bronchial walls, increased bronchovascular markings with ill-defined pulmonary vasculature and ring shadows that are created by viewing terminal bronchi front-on can direct towards a diagnosis of bronchiectasis. Nevertheless, CT is considered the superior imaging modality. Three classical imagining features observed include the tram-track sign, signet sign and honeycomb appearance.
These congenital lesions are observed on chest radiography as variably sized yet well circumscribed areas of increased opacity . Furthermore, CT imaging can be used and demonstrates spherical or tubule masses of homogenous or variable attenuation . Moreover, MRI imaging may also be utilised. In particular, areas corresponding to bronchogenic cysts on T1 weighted MRI demonstrates variable signal intensity, whereas, on T2 weighted MRI high signal intensity regions are observed .
Pus which gathers in the pleural space is normally a consequence of a background pathology process. Chest radiography and CT are routinely requested when there is any suspicion of pus in the pleural space . The former demonstrates a unilateral-asymmetric biconvex fluid level which can be difficult to distinguish from a pleural effusion. While the latter identifies fluid collections as increased density in the pleural space which can sometimes arise with locules of gas. In addition, a thickened pleura may be observed and the split pleura sign can be appreciated.
Chest radiography and CT imaging are typically utilised to investigate this circumscribed collection of pus within lung tissue . Chest radiography typically demonstrates a cavity in the lung which contains a fluid level. CT imaging also identifies the cavity and the air-fluid level, as well as, demarcating the wall of the cavity.
Inflammation of the alveoli produces characteristic radiological features and signs which are identified with chest radiography and CT imaging . Less frequently MRI is used . In particular, with a chest radiograph areas of homogenous opacification are typically seen in a lobar pattern. Furthermore, when utilising CT imaging ground glass opacity is observed correspondingly in a lobar pattern. However, if the inflammation is extensive non-lobar patterned segments may be involved. Less commonly MRI is used; on a T2 weighted scan areas of high signal are observed from the lung areas that are infected.
Chest radiography and CT imaging are normally used when investigating suspected pulmonary positioned neoplasms . When utilising chest radiography, no specific findings as such are observed. However, radiological features such as hilar or perihilar opacification with mediastinal widening and central or peripheral nodules/zones of increased opacification may be indicative of a pulmonary neoplasm. With CT imaging, greater detail can be determined with reference to viewing of enlarged lymph nodes, infiltration of neoplasm into adjacent structures, lung atelectasis, cavitation and haemorrhage or necrosis of lung tissue associated with a neoplasm.
Resection of the congenital pulmonary malformation was considered as it was deemed to be the likely cause of this patient’s bronchiectasis features. Furthermore, it was hypothesised that the aberrant artery may be causing a steal like syndrome at the coeliac trunk which could potentially be causing her abdominal pain. However, she was subsequently managed conservatively after a respiratory follow up as firstly her lung function test was reported as sufficient, secondly, she did not encounter any further respiratory infections and finally her abdominal pain appeared to resolve with the use of regular analgesia.
A hybrid pulmonary sequestration (PMS) and congenital cystic adenomatoid malformation (CCAM) is a bronchopulmonary malformation that can be proficiently identified on a contrast enhanced CT scan. From this imaging modality the essential radiological description that is required for diagnosis includes the appreciation of an atypical artery supplying an abnormal territory of lung parenchyma that is noted to contain multiple cystic projections alongside a rudimentary bronchial tree.