Pulmonary Sequestration : Development, Types, Investigations, Treatment

• A mixed group of congenital malformations includes pulmonary sequestration. The name itself suggests sequestration, which means separation or isolation. If it is basically a congenital disorder in which there is aberrant lung tissue that does not get connected with the bronchus, and often its vascular supply is also found to be very different from the normal lung tissue. Pulmonary sequestration refers to a congenital anomaly where the lung tissue is not attached to the bronchus. Receive arterial supply from the systemic circulation, i.e., aortic branches.
• Drain venous blood into the inferior vena cava ( extralobar type) or into the pulmonary veins (intralobar type).  Functioned as a space-occupying lesion (SOL) and did not take part in gas exchange.  It is solid cystic lesion, occupies space and causes compressive symptoms and repeated infections, but they are not of any use as they don't take part in gas exchange. Collateral ventilation within intrapulmonary lesions via pores of Kohn can occur, rarely seen in pulmonary sequestration.

Why Does It Develops?

• There are three theories for the development of sequestration: -
  • First theory-sequestration develops as an aberrant outgrowth of the esophagus in embryonic life. Mainly, it says it is a derivative of the GI, which is a kind of metamorphosis into pulmonary tissue. Evidence of gastric, pancreatic, and rarely esophageal tissue in the sequestration mass.  This theory is not valid based on histopathological examination findings; no entity has been found. that esophageal outgrowth is not as common as it has been seen.  Some subsets of patients develop sequestration based on this mechanism,
  • Second theory-sequestration is not a congenital disorder; it is an acquired disorder. It occurs due to infection, inflammation followed by cystic changes occurring in specific portions of pulmonary tissue.  Evidence for this pulmonary sequestration is not that common in many newborn series, but its incidence slightly increased in late infancy.
  • Third theory, it is not a dependent entity at all. It is a variant or subtype of congenital pulmonary airway malformation (CPAM).

Also Read: Image Based Questions On Immune System

Common Features

• Chronic coughs,  Wheezing and/or recurrent pneumonia, Rarely, patients with sequestration present with hemoptysis, i.e., blood in the sputum, Physical Examination Findings- An area of dullness in percussion, decreased breath sounds over the lesion, uring infection, crackles may also be present, ue to aberrant vessels, a continuous or purely systolic murmur may be head-over-back.

Types Of Sequestration

• There are two varieties: the intralobar form and the extralobar form. The intralobar form will be inside the lobe of the lung, and it will not have an independent pleura. Most common variety. The extralobar will be outside the lung, and  it will have its own pleural coverage. In intrapulmonary sequestration present with infections, so repeated infections in that cyst are common, and because of those repeated infections, there is often a mass lesion that sometimes becomes cystic, and air fluid levels can also be seen.
• Extrapulmonary sequestration can also be sub-diaphragmatic, i.e., decompression outside the thorax in the abdominal cavity below the diaphragm can be present.

Q. What Is The Percentage Of Congenital Malformations In Sequestration?

Ans. Intrapulmonary sequestration that either does not show any congenital malformation or, if it does, is rare. So around 2% of intrapulmonary sequestrations show associated congenital malformations.

• In the case of 100 children with intrapulmonary sequestration or intralobar sequestration, only 2% were found to have congenital malformations. Extrapulmonary disease is associated with congenital malformations and is seen in 50% of these children.

Chest-X Ray Finding

• The chest X- ray finding - solid cystic mass in the absence of bronchial tissue. Diagnosis - sequestration of the lungs.

Q.Which variety will go for sequestration of lungs in diagnosis?

• It is present in the right lungs in the lower lobes, and they are solid cystic masses that are visible. So, it is an intrapulmonary sequestration that is present.

Investigations

• Prenatal USG, Chest-X ray, CT with contrast -investigation of choice,  CT shows the extent and vascularity of the disease. The goal standard is MR angiography; it is not always needed.

Treatment

• Treatment - surgical resection in most cases. In intrapulmonary variety, surgical resection in the form of either lobectomy or segmental resection.In extrapulmonary or extralobular variety,-surgical resection.Alternative- coil embolization of the supplying vessel. Its a non-surgical, radiology-guided, semi-invasive procedure that can be an alternative to surgical resection.

Bronchogenic Cysts

• Foregut derivative arises due to abnormal budding at the tracheal diverticulum before the 16th week of gestation. Lined by ciliated epithelium. Mostly, located on the right side, adjacent to a midline structure(most common). Peripheral lower lobes, perihilar region. They are lined by ciliated epithelium, if repeated infections occur in the bronchogenic cyst, this ciliated epithelium may be lost, and so the histological diagnosis of the bronchogenic cyst may be very difficult.
• That is why the bronchogenic cyst comes to attention in later life, in adulthood, and if there is a history of recurrent infections in the past, when doing histopathology, ciliated epithelium is not found, and again, it produces a diagnostic dilemma.In children, most of the ciliated epithelium is still intact.

Bronchogenic X-RAY

• It is a chest X-ray showing the features of a bronchogenic cyst.

Clinical Features, Diagnosis, And Management

• In clinical features- Fever, chest pain and a productive cough due to infections in the cyst.  It is very prone to infections. Dysphagia, some types of small cysts can even be asymptomatic.  For investigations or diagnosis: -  chest X-rays,  CT and MRI. A CT or MRI is needed for most of these patients.

Treatment

• Surgical excision because of the high rate of repeated infections. Infected cyst:- Antibiotics are used first. Later surgery will be performed. 

Also Read: Image Based Questions On Respiratory System

Congenital Pulmonary Lymphangiectasia

• Congenital present in the lungs; lymphang means lymph vessels are dilated. Abnormally dilated lymph vessels in the pulmonary system are called congenital pulmonary lymphangiectasia (CPL). CPL can arise in three scenarios-
• First scenario, whenever there is pulmonary venous obstruction,
  • e.g., any congenital heart disease. In any congenital disease where there is pulmonary venous obstruction due to back phrasal changes and due to pressure dynamics, the lymph vessels may get enlarged and dilated. So that is pulmonary venous obstruction.
• Second scenario, this lymphangiectasia can develop as part of a generalized lymphangiectasia. Lymphangiectasia can develop all over the body; they are present in the gut, lungs, and even the limbs. Generalized lymphangiectasia, they are usually milder in nature. The pulmonary manifestations are milder, and they occur in conditions like Noonan syndrome, Down syndrome, and  Turner syndrome.
• Third scenario, isolated /primary pulmonary lymphangiectasia, i.e., occur only in the lungs , and they occur as part of a disease process called Gorham-Stout disease. Gorham-Stout disease is also called "vanishing bone disease."This is a condition that is characterized by chylous effusion in  thorax and abdomen.Destructive bony cysts,  Lymphangiomas elsewhere in the body. Lymphangiomas are the other manifestations.

Clinical Features

• Clinical features depend on the underlined conditions. They are mild in the generalized forms where they are localized to the lungs. If they are part of pulmonary venous obstruction, they will be severe. Clinical features can be asymptomatic or symptomatic.
• Clinical features: -  Chylothorax, associated with dyspnea and cyanosis in the child. Dyspnea and cyanosis are most common with pulmonary venous obstruction and associated with other systemic diseases.
• Investigations: - lymphangiogram,  lung biopsy 

Treatment

• Supportive therapy:- Oxygen and mechanical ventilation to these children. Diuretics. Nutritional support in the form of medium-chain triglycerides (MCT) supplementation.
• Octreotide found useful in decreasing chylous effusion in many patients.

Also Read: Microdeletion Syndromes Part-3 : Williams Syndrome,  Rubinstein Taybi Syndrome, Smith Magenis  Syndrome

Broncho-billiary Fistula

• Fistulas communication between the bronchus and the biliary tract. Most commonly, occurs on the right side.  There is communication between the bronchus of the right middle lobe and the left hepatic biliary tract. It can be congenital (mc), or acquired form. Congenital forms are more common in children. Acquired form can occur as a complication of pyogenic liver abscess, but  not common in children.
• Females are more commonly affected than males. Recurrent infection in infancy is the common pattern. Some may have a delayed presentation. A definitive diagnosis requires endoscopy or exploratory surgery. During exploratory surgery,there is often a need to perform an intraoperative cholangiogram, where the dye is injected, and pattern is seen.
• Treatment - surgical excision of the entire intrathoracic portion of the fistula. Whenever there are recurrent infections in infancy,(not very common). Young infants will not be able to produce sputum.   Bile stained  expectoration or sputum production,  the signs seen  in older children.

Cholangiogram

• The white color arrow  show patent biliary tract; the dye was injected; and the dye is going all the way into the lungs. Diagnosis -bronchobiliary fistula.

Also Read: Key Points And Recommendations In Pediatric Advanced Life Support

Lung Hernia

• When lung exceeds or comes out of its thoracic boundary, it is called a lung hernia. Lung hernia refers to a lung extending beyond its thoracic boundaries.  Herniation of lung tissue occurring into the neck region, called as cervical type of lung hernia. The likely diagnosis - lung herniation.

Causes Of Lung Hernia

• It can be broadly divided into congenital causes and acquired causes. The congenital causes:-  Due to weakness of the muscles or any rib abnormalities. The acquired causes:-  Due to  thoracic trauma or thoracic surgery, or raised  intrathoracic pressure due to chronic coughing.  Chronic cough: - E.g., in cystic fibrosis, allergic cough, or asthma, there will be acquired lung herniation.

Cervical Herniation 

• The most common site of lung herniation is cervical herniation, in more than 50% of congenital forms and more than 90% of acquired forms. Cervical herniation -Occur between the scalenus anterior muscle and the sternocleidomastoid muscle. It can occur on the right side as well as the left side.
• Cervical herniation risk increased – Due to weakness of the suprapleural membrane (Sibson's fascia).  Cervical herniations were also called Sibson's herniations. It can develop on other sites:- paravertebral and parasternal. The parasternal arise due to weakness of the external intercostal muscles. Both paravertebral and parasternal are associated with rib abnormalities.

Clinical Features

• Asymptomatic. Appear as neck mass.  Neck mass becomes prominent during coughing or Valsalva. A chest X-ray and CT scan are done. Treatment-  only if the patient needs therapy for cosmetic reasons. or if there any coexisting abnormalities, very rare.  it is a benign condition that requires therapy.

Hope you found this blog helpful for your NEET SS Pediatrics pulmonology preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.